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Current implementation calls kprobe related functions before doing
ftrace recursion check in fprobe_kprobe_handler, which opens door
to kernel crash due to stack recursion if preempt_count_{add, sub}
is traceable in kprobe_busy_{begin, end}.
Things goes like this without this patch quoted from Steven:
"
fprobe_kprobe_handler() {
kprobe_busy_begin() {
preempt_disable() {
preempt_count_add() { <-- trace
fprobe_kprobe_handler() {
[ wash, rinse, repeat, CRASH!!! ]
"
By refactoring the common part out of fprobe_kprobe_handler and
fprobe_handler and call ftrace recursion detection at the very beginning,
the whole fprobe_kprobe_handler is free from recursion.
[ Fix the indentation of __fprobe_handler() parameters. ]
Link: https://lore.kernel.org/all/[email protected]/
Fixes: ab51e15d535e ("fprobe: Introduce FPROBE_FL_KPROBE_SHARED flag for fprobe")
Signed-off-by: Ze Gao <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Cc: [email protected]
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
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This patch replaces preempt_{disable, enable} with its corresponding
notrace version in rethook_trampoline_handler so no worries about stack
recursion or overflow introduced by preempt_count_{add, sub} under
fprobe + rethook context.
Link: https://lore.kernel.org/all/[email protected]/
Fixes: 54ecbe6f1ed5 ("rethook: Add a generic return hook")
Signed-off-by: Ze Gao <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Cc: <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
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Building with 'make W=1' reveals two function definitions without
a previous prototype in the audit code:
lib/compat_audit.c:32:5: error: no previous prototype for 'audit_classify_compat_syscall' [-Werror=missing-prototypes]
kernel/audit.c:1813:14: error: no previous prototype for 'audit_serial' [-Werror=missing-prototypes]
The first one needs a declaration from linux/audit.h but cannot
include that header without causing conflicting (compat) syscall number
definitions, so move the it into linux/audit_arch.h.
The second one is declared conditionally based on CONFIG_AUDITSYSCALL
but needed as a local function even when that option is disabled, so
move the declaration out of the #ifdef block.
Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Paul Moore <[email protected]>
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The commit 39d954200bf6 ("fprobe: Skip exit_handler if entry_handler returns
!0") introduced a hidden dependency of 'ret' local variable in the
fprobe_handler(), Smatch warns the `ret` can be accessed without
initialization.
kernel/trace/fprobe.c:59 fprobe_handler()
error: uninitialized symbol 'ret'.
kernel/trace/fprobe.c
49 fpr->entry_ip = ip;
50 if (fp->entry_data_size)
51 entry_data = fpr->data;
52 }
53
54 if (fp->entry_handler)
55 ret = fp->entry_handler(fp, ip, ftrace_get_regs(fregs), entry_data);
ret is only initialized if there is an ->entry_handler
56
57 /* If entry_handler returns !0, nmissed is not counted. */
58 if (rh) {
rh is only true if there is an ->exit_handler. Presumably if you have
and ->exit_handler that means you also have a ->entry_handler but Smatch
is not smart enough to figure it out.
--> 59 if (ret)
^^^
Warning here.
60 rethook_recycle(rh);
61 else
62 rethook_hook(rh, ftrace_get_regs(fregs), true);
63 }
64 out:
65 ftrace_test_recursion_unlock(bit);
66 }
Link: https://lore.kernel.org/all/168100731160.79534.374827110083836722.stgit@devnote2/
Reported-by: Dan Carpenter <[email protected]>
Link: https://lore.kernel.org/all/[email protected]
Fixes: 39d954200bf6 ("fprobe: Skip exit_handler if entry_handler returns !0")
Acked-by: Dan Carpenter <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
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It's trivial for user to trigger "verifier log line truncated" warning,
as verifier has a fixed-sized buffer of 1024 bytes (as of now), and there are at
least two pieces of user-provided information that can be output through
this buffer, and both can be arbitrarily sized by user:
- BTF names;
- BTF.ext source code lines strings.
Verifier log buffer should be properly sized for typical verifier state
output. But it's sort-of expected that this buffer won't be long enough
in some circumstances. So let's drop the check. In any case code will
work correctly, at worst truncating a part of a single line output.
Reported-by: [email protected]
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
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https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
Daniel Borkmann says:
====================
pull-request: bpf-next 2023-05-16
We've added 57 non-merge commits during the last 19 day(s) which contain
a total of 63 files changed, 3293 insertions(+), 690 deletions(-).
The main changes are:
1) Add precision propagation to verifier for subprogs and callbacks,
from Andrii Nakryiko.
2) Improve BPF's {g,s}setsockopt() handling with wrong option lengths,
from Stanislav Fomichev.
3) Utilize pahole v1.25 for the kernel's BTF generation to filter out
inconsistent function prototypes, from Alan Maguire.
4) Various dyn-pointer verifier improvements to relax restrictions,
from Daniel Rosenberg.
5) Add a new bpf_task_under_cgroup() kfunc for designated task,
from Feng Zhou.
6) Unblock tests for arm64 BPF CI after ftrace supporting direct call,
from Florent Revest.
7) Add XDP hint kfunc metadata for RX hash/timestamp for igc,
from Jesper Dangaard Brouer.
8) Add several new dyn-pointer kfuncs to ease their usability,
from Joanne Koong.
9) Add in-depth LRU internals description and dot function graph,
from Joe Stringer.
10) Fix KCSAN report on bpf_lru_list when accessing node->ref,
from Martin KaFai Lau.
11) Only dump unprivileged_bpf_disabled log warning upon write,
from Kui-Feng Lee.
12) Extend test_progs to directly passing allow/denylist file,
from Stephen Veiss.
13) Fix BPF trampoline memleak upon failure attaching to fentry,
from Yafang Shao.
14) Fix emitting struct bpf_tcp_sock type in vmlinux BTF,
from Yonghong Song.
* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next: (57 commits)
bpf: Fix memleak due to fentry attach failure
bpf: Remove bpf trampoline selector
bpf, arm64: Support struct arguments in the BPF trampoline
bpftool: JIT limited misreported as negative value on aarch64
bpf: fix calculation of subseq_idx during precision backtracking
bpf: Remove anonymous union in bpf_kfunc_call_arg_meta
bpf: Document EFAULT changes for sockopt
selftests/bpf: Correctly handle optlen > 4096
selftests/bpf: Update EFAULT {g,s}etsockopt selftests
bpf: Don't EFAULT for {g,s}setsockopt with wrong optlen
libbpf: fix offsetof() and container_of() to work with CO-RE
bpf: Address KCSAN report on bpf_lru_list
bpf: Add --skip_encoding_btf_inconsistent_proto, --btf_gen_optimized to pahole flags for v1.25
selftests/bpf: Accept mem from dynptr in helper funcs
bpf: verifier: Accept dynptr mem as mem in helpers
selftests/bpf: Check overflow in optional buffer
selftests/bpf: Test allowing NULL buffer in dynptr slice
bpf: Allow NULL buffers in bpf_dynptr_slice(_rw)
selftests/bpf: Add testcase for bpf_task_under_cgroup
bpf: Add bpf_task_under_cgroup() kfunc
...
====================
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
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If it fails to attach fentry, the allocated bpf trampoline image will be
left in the system. That can be verified by checking /proc/kallsyms.
This meamleak can be verified by a simple bpf program as follows:
SEC("fentry/trap_init")
int fentry_run()
{
return 0;
}
It will fail to attach trap_init because this function is freed after
kernel init, and then we can find the trampoline image is left in the
system by checking /proc/kallsyms.
$ tail /proc/kallsyms
ffffffffc0613000 t bpf_trampoline_6442453466_1 [bpf]
ffffffffc06c3000 t bpf_trampoline_6442453466_1 [bpf]
$ bpftool btf dump file /sys/kernel/btf/vmlinux | grep "FUNC 'trap_init'"
[2522] FUNC 'trap_init' type_id=119 linkage=static
$ echo $((6442453466 & 0x7fffffff))
2522
Note that there are two left bpf trampoline images, that is because the
libbpf will fallback to raw tracepoint if -EINVAL is returned.
Fixes: e21aa341785c ("bpf: Fix fexit trampoline.")
Signed-off-by: Yafang Shao <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Song Liu <[email protected]>
Cc: Jiri Olsa <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
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After commit e21aa341785c ("bpf: Fix fexit trampoline."), the selector is only
used to indicate how many times the bpf trampoline image are updated and been
displayed in the trampoline ksym name. After the trampoline is freed, the
selector will start from 0 again. So the selector is a useless value to the
user. We can remove it.
If the user want to check whether the bpf trampoline image has been updated
or not, the user can compare the address. Each time the trampoline image is
updated, the address will change consequently. Jiri also pointed out another
issue that perf is still using the old name "bpf_trampoline_%lu", so this
change can fix the issue in perf.
Fixes: e21aa341785c ("bpf: Fix fexit trampoline.")
Signed-off-by: Yafang Shao <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Song Liu <[email protected]>
Cc: Jiri Olsa <[email protected]>
Link: https://lore.kernel.org/bpf/ZFvOOlrmHiY9AgXE@krava
Link: https://lore.kernel.org/bpf/[email protected]
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Subsequent instruction index (subseq_idx) is an index of an instruction
that was verified/executed by verifier after the currently processed
instruction. It is maintained during precision backtracking processing
and is used to detect various subprog calling conditions.
This patch fixes the bug with incorrectly resetting subseq_idx to -1
when going from child state to parent state during backtracking. If we
don't maintain correct subseq_idx we can misidentify subprog calls
leading to precision tracking bugs.
One such case was triggered by test_global_funcs/global_func9 test where
global subprog call happened to be the very last instruction in parent
state, leading to subseq_idx==-1, triggering WARN_ONCE:
[ 36.045754] verifier backtracking bug
[ 36.045764] WARNING: CPU: 13 PID: 2073 at kernel/bpf/verifier.c:3503 __mark_chain_precision+0xcc6/0xde0
[ 36.046819] Modules linked in: aesni_intel(E) crypto_simd(E) cryptd(E) kvm_intel(E) kvm(E) irqbypass(E) i2c_piix4(E) serio_raw(E) i2c_core(E) crc32c_intel)
[ 36.048040] CPU: 13 PID: 2073 Comm: test_progs Tainted: G W OE 6.3.0-07976-g4d585f48ee6b-dirty #972
[ 36.048783] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.0-59-gc9ba5276e321-prebuilt.qemu.org 04/01/2014
[ 36.049648] RIP: 0010:__mark_chain_precision+0xcc6/0xde0
[ 36.050038] Code: 3d 82 c6 05 bb 35 32 02 01 e8 66 21 ec ff 0f 0b b8 f2 ff ff ff e9 30 f5 ff ff 48 c7 c7 f3 61 3d 82 4c 89 0c 24 e8 4a 21 ec ff <0f> 0b 4c0
With the fix precision tracking across multiple states works correctly now:
mark_precise: frame0: last_idx 45 first_idx 38 subseq_idx -1
mark_precise: frame0: regs=r8 stack= before 44: (61) r7 = *(u32 *)(r10 -4)
mark_precise: frame0: regs=r8 stack= before 43: (85) call pc+41
mark_precise: frame0: regs=r8 stack= before 42: (07) r1 += -48
mark_precise: frame0: regs=r8 stack= before 41: (bf) r1 = r10
mark_precise: frame0: regs=r8 stack= before 40: (63) *(u32 *)(r10 -48) = r1
mark_precise: frame0: regs=r8 stack= before 39: (b4) w1 = 0
mark_precise: frame0: regs=r8 stack= before 38: (85) call pc+38
mark_precise: frame0: parent state regs=r8 stack=: R0_w=scalar() R1_w=map_value(off=4,ks=4,vs=8,imm=0) R6=1 R7_w=scalar() R8_r=P0 R10=fpm
mark_precise: frame0: last_idx 36 first_idx 28 subseq_idx 38
mark_precise: frame0: regs=r8 stack= before 36: (18) r1 = 0xffff888104f2ed14
mark_precise: frame0: regs=r8 stack= before 35: (85) call pc+33
mark_precise: frame0: regs=r8 stack= before 33: (18) r1 = 0xffff888104f2ed10
mark_precise: frame0: regs=r8 stack= before 32: (85) call pc+36
mark_precise: frame0: regs=r8 stack= before 31: (07) r1 += -4
mark_precise: frame0: regs=r8 stack= before 30: (bf) r1 = r10
mark_precise: frame0: regs=r8 stack= before 29: (63) *(u32 *)(r10 -4) = r7
mark_precise: frame0: regs=r8 stack= before 28: (4c) w7 |= w0
mark_precise: frame0: parent state regs=r8 stack=: R0_rw=scalar() R6=1 R7_rw=scalar() R8_rw=P0 R10=fp0 fp-48_r=mmmmmmmm
mark_precise: frame0: last_idx 27 first_idx 16 subseq_idx 28
mark_precise: frame0: regs=r8 stack= before 27: (85) call pc+31
mark_precise: frame0: regs=r8 stack= before 26: (b7) r1 = 0
mark_precise: frame0: regs=r8 stack= before 25: (b7) r8 = 0
Note how subseq_idx starts out as -1, then is preserved as 38 and then 28 as we
go up the parent state chain.
Reported-by: Alexei Starovoitov <[email protected]>
Fixes: fde2a3882bd0 ("bpf: support precision propagation in the presence of subprogs")
Signed-off-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
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For kfuncs like bpf_obj_drop and bpf_refcount_acquire - which take
user-defined types as input - the verifier needs to track the specific
type passed in when checking a particular kfunc call. This requires
tracking (btf, btf_id) tuple. In commit 7c50b1cb76ac
("bpf: Add bpf_refcount_acquire kfunc") I added an anonymous union with
inner structs named after the specific kfuncs tracking this information,
with the goal of making it more obvious which kfunc this data was being
tracked / expected to be tracked on behalf of.
In a recent series adding a new user of this tuple, Alexei mentioned
that he didn't like this union usage as it doesn't really help with
readability or bug-proofing ([0]). In an offline convo we agreed to
have the tuple be fields (arg_btf, arg_btf_id), with comments in
bpf_kfunc_call_arg_meta definition enumerating the uses of the fields by
kfunc-specific handling logic. Such a pattern is used by struct
bpf_reg_state without trouble.
Accordingly, this patch removes the anonymous union in favor of arg_btf
and arg_btf_id fields and comment enumerating their current uses. The
patch also removes struct btf_and_id, which was only being used by the
removed union's inner structs.
This is a mechanical change, existing linked_list and rbtree tests will
validate that correct (btf, btf_id) are being passed.
[0]: https://lore.kernel.org/bpf/20230505021707.vlyiwy57vwxglbka@dhcp-172-26-102-232.dhcp.thefacebook.com
Signed-off-by: Dave Marchevsky <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
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Some netdevices may get unregistered before late_initcall(),
we have to move the hashtable init earlier.
Fixes: f1fc43d03946 ("bpf: Move offload initialization into late_initcall")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217399
Signed-off-by: Jakub Kicinski <[email protected]>
Acked-by: Stanislav Fomichev <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
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There is often significant latency in the early stages of CPU bringup, and
time is wasted by waking each CPU (e.g. with SIPI/INIT/INIT on x86) and
then waiting for it to respond before moving on to the next.
Allow a platform to enable parallel setup which brings all to be onlined
CPUs up to the CPUHP_BP_KICK_AP state. While this state advancement on the
control CPU (BP) is single-threaded the important part is the last state
CPUHP_BP_KICK_AP which wakes the to be onlined CPUs up.
This allows the CPUs to run up to the first sychronization point
cpuhp_ap_sync_alive() where they wait for the control CPU to release them
one by one for the full onlining procedure.
This parallelism depends on the CPU hotplug core sync mechanism which
ensures that the parallel brought up CPUs wait for release before touching
any state which would make the CPU visible to anything outside the hotplug
control mechanism.
To handle the SMT constraints of X86 correctly the bringup happens in two
iterations when CONFIG_HOTPLUG_SMT is enabled. The control CPU brings up
the primary SMT threads of each core first, which can load the microcode
without the need to rendevouz with the thread siblings. Once that's
completed it brings up the secondary SMT threads.
Co-developed-by: David Woodhouse <[email protected]>
Signed-off-by: David Woodhouse <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Michael Kelley <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc
Tested-by: Guilherme G. Piccoli <[email protected]> # Steam Deck
Link: https://lore.kernel.org/r/[email protected]
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The bring up logic of a to be onlined CPU consists of several parts, which
are considered to be a single hotplug state:
1) Control CPU issues the wake-up
2) To be onlined CPU starts up, does the minimal initialization,
reports to be alive and waits for release into the complete bring-up.
3) Control CPU waits for the alive report and releases the upcoming CPU
for the complete bring-up.
Allow to split this into two states:
1) Control CPU issues the wake-up
After that the to be onlined CPU starts up, does the minimal
initialization, reports to be alive and waits for release into the
full bring-up. As this can run after the control CPU dropped the
hotplug locks the code which is executed on the AP before it reports
alive has to be carefully audited to not violate any of the hotplug
constraints, especially not modifying any of the various cpumasks.
This is really only meant to avoid waiting for the AP to react on the
wake-up. Of course an architecture can move strict CPU related setup
functionality, e.g. microcode loading, with care before the
synchronization point to save further pointless waiting time.
2) Control CPU waits for the alive report and releases the upcoming CPU
for the complete bring-up.
This allows that the two states can be split up to run all to be onlined
CPUs up to state #1 on the control CPU and then at a later point run state
#2. This spares some of the latencies of the full serialized per CPU
bringup by avoiding the per CPU wakeup/wait serialization. The assumption
is that the first AP already waits when the last AP has been woken up. This
obvioulsy depends on the hardware latencies and depending on the timings
this might still not completely eliminate all wait scenarios.
This split is just a preparatory step for enabling the parallel bringup
later. The boot time bringup is still fully serialized. It has a separate
config switch so that architectures which want to support parallel bringup
can test the split of the CPUHP_BRINGUG step separately.
To enable this the architecture must support the CPU hotplug core sync
mechanism and has to be audited that there are no implicit hotplug state
dependencies which require a fully serialized bringup.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Michael Kelley <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc
Tested-by: Guilherme G. Piccoli <[email protected]> # Steam Deck
Link: https://lore.kernel.org/r/[email protected]
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Commit dce1ca0525bf ("sched/scs: Reset task stack state in bringup_cpu()")
ensured that the shadow call stack and KASAN poisoning were removed from
a CPU's stack each time that CPU is brought up, not just once.
This is not incorrect. However, with parallel bringup the idle thread setup
will happen at a different step. As a consequence the cleanup in
bringup_cpu() would be too late.
Move the SCS/KASAN cleanup to the generic _cpu_up() function instead,
which already ensures that the new CPU's stack is available, purely to
allow for early failure. This occurs when the CPU to be brought up is
in the CPUHP_OFFLINE state, which should correctly do the cleanup any
time the CPU has been taken down to the point where such is needed.
Signed-off-by: David Woodhouse <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Mark Rutland <[email protected]>
Tested-by: Mark Rutland <[email protected]>
Tested-by: Michael Kelley <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc
Tested-by: Guilherme G. Piccoli <[email protected]> # Steam Deck
Link: https://lore.kernel.org/r/[email protected]
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All users converted to the hotplug core mechanism.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Michael Kelley <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc
Tested-by: Guilherme G. Piccoli <[email protected]> # Steam Deck
Link: https://lore.kernel.org/r/[email protected]
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No more users.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Michael Kelley <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc
Tested-by: Guilherme G. Piccoli <[email protected]> # Steam Deck
Link: https://lore.kernel.org/r/[email protected]
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The CPU state tracking and synchronization mechanism in smpboot.c is
completely independent of the hotplug code and all logic around it is
implemented in architecture specific code.
Except for the state reporting of the AP there is absolutely nothing
architecture specific and the sychronization and decision functions can be
moved into the generic hotplug core code.
Provide an integrated variant and add the core synchronization and decision
points. This comes in two flavours:
1) DEAD state synchronization
Updated by the architecture code once the AP reaches the point where
it is ready to be torn down by the control CPU, e.g. by removing power
or clocks or tear down via the hypervisor.
The control CPU waits for this state to be reached with a timeout. If
the state is reached an architecture specific cleanup function is
invoked.
2) Full state synchronization
This extends #1 with AP alive synchronization. This is new
functionality, which allows to replace architecture specific wait
mechanims, e.g. cpumasks, completely.
It also prevents that an AP which is in a limbo state can be brought
up again. This can happen when an AP failed to report dead state
during a previous off-line operation.
The dead synchronization is what most architectures use. Only x86 makes a
bringup decision based on that state at the moment.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Michael Kelley <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc
Tested-by: Guilherme G. Piccoli <[email protected]> # Steam Deck
Link: https://lore.kernel.org/r/[email protected]
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There is no harm to hold sparse_irq lock until the upcoming CPU completes
in cpuhp_online_idle(). This allows to remove cpu_online() synchronization
from architecture code.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Michael Kelley <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc
Tested-by: Guilherme G. Piccoli <[email protected]> # Steam Deck
Link: https://lore.kernel.org/r/[email protected]
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No point in keeping them around.
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Tested-by: Michael Kelley <[email protected]>
Tested-by: Oleksandr Natalenko <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc
Tested-by: Guilherme G. Piccoli <[email protected]> # Steam Deck
Link: https://lore.kernel.org/r/[email protected]
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fix from Borislav Petkov:
- Make sure __down_read_common() is always inlined so that the callers'
names land in traceevents output and thus the blocked function can be
identified
* tag 'locking_urgent_for_v6.4_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking/rwsem: Add __always_inline annotation to __down_read_common() and inlined callers
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Borislav Petkov:
- Make sure the PEBS buffer is flushed before reprogramming the
hardware so that the correct record sizes are used
- Update the sample size for AMD BRS events
- Fix a confusion with using the same on-stack struct with different
events in the event processing path
* tag 'perf_urgent_for_v6.4_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf/x86/intel/ds: Flush PEBS DS when changing PEBS_DATA_CFG
perf/x86: Fix missing sample size update on AMD BRS
perf/core: Fix perf_sample_data not properly initialized for different swevents in perf_tp_event()
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fix from Borislav Petkov:
- Fix a couple of kernel-doc warnings
* tag 'sched_urgent_for_v6.4_rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched: fix cid_lock kernel-doc warnings
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With the way the hooks implemented right now, we have a special
condition: optval larger than PAGE_SIZE will expose only first 4k into
BPF; any modifications to the optval are ignored. If the BPF program
doesn't handle this condition by resetting optlen to 0,
the userspace will get EFAULT.
The intention of the EFAULT was to make it apparent to the
developers that the program is doing something wrong.
However, this inadvertently might affect production workloads
with the BPF programs that are not too careful (i.e., returning EFAULT
for perfectly valid setsockopt/getsockopt calls).
Let's try to minimize the chance of BPF program screwing up userspace
by ignoring the output of those BPF programs (instead of returning
EFAULT to the userspace). pr_info_once those cases to
the dmesg to help with figuring out what's going wrong.
Fixes: 0d01da6afc54 ("bpf: implement getsockopt and setsockopt hooks")
Suggested-by: Martin KaFai Lau <[email protected]>
Signed-off-by: Stanislav Fomichev <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Martin KaFai Lau <[email protected]>
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KCSAN reported a data-race when accessing node->ref.
Although node->ref does not have to be accurate,
take this chance to use a more common READ_ONCE() and WRITE_ONCE()
pattern instead of data_race().
There is an existing bpf_lru_node_is_ref() and bpf_lru_node_set_ref().
This patch also adds bpf_lru_node_clear_ref() to do the
WRITE_ONCE(node->ref, 0) also.
==================================================================
BUG: KCSAN: data-race in __bpf_lru_list_rotate / __htab_lru_percpu_map_update_elem
write to 0xffff888137038deb of 1 bytes by task 11240 on cpu 1:
__bpf_lru_node_move kernel/bpf/bpf_lru_list.c:113 [inline]
__bpf_lru_list_rotate_active kernel/bpf/bpf_lru_list.c:149 [inline]
__bpf_lru_list_rotate+0x1bf/0x750 kernel/bpf/bpf_lru_list.c:240
bpf_lru_list_pop_free_to_local kernel/bpf/bpf_lru_list.c:329 [inline]
bpf_common_lru_pop_free kernel/bpf/bpf_lru_list.c:447 [inline]
bpf_lru_pop_free+0x638/0xe20 kernel/bpf/bpf_lru_list.c:499
prealloc_lru_pop kernel/bpf/hashtab.c:290 [inline]
__htab_lru_percpu_map_update_elem+0xe7/0x820 kernel/bpf/hashtab.c:1316
bpf_percpu_hash_update+0x5e/0x90 kernel/bpf/hashtab.c:2313
bpf_map_update_value+0x2a9/0x370 kernel/bpf/syscall.c:200
generic_map_update_batch+0x3ae/0x4f0 kernel/bpf/syscall.c:1687
bpf_map_do_batch+0x2d9/0x3d0 kernel/bpf/syscall.c:4534
__sys_bpf+0x338/0x810
__do_sys_bpf kernel/bpf/syscall.c:5096 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5094 [inline]
__x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5094
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
read to 0xffff888137038deb of 1 bytes by task 11241 on cpu 0:
bpf_lru_node_set_ref kernel/bpf/bpf_lru_list.h:70 [inline]
__htab_lru_percpu_map_update_elem+0x2f1/0x820 kernel/bpf/hashtab.c:1332
bpf_percpu_hash_update+0x5e/0x90 kernel/bpf/hashtab.c:2313
bpf_map_update_value+0x2a9/0x370 kernel/bpf/syscall.c:200
generic_map_update_batch+0x3ae/0x4f0 kernel/bpf/syscall.c:1687
bpf_map_do_batch+0x2d9/0x3d0 kernel/bpf/syscall.c:4534
__sys_bpf+0x338/0x810
__do_sys_bpf kernel/bpf/syscall.c:5096 [inline]
__se_sys_bpf kernel/bpf/syscall.c:5094 [inline]
__x64_sys_bpf+0x43/0x50 kernel/bpf/syscall.c:5094
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x01 -> 0x00
Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11241 Comm: syz-executor.3 Not tainted 6.3.0-rc7-syzkaller-00136-g6a66fdd29ea1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/30/2023
==================================================================
Reported-by: [email protected]
Signed-off-by: Martin KaFai Lau <[email protected]>
Acked-by: Yonghong Song <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>
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Running the 'kfree_rcu_test' test case [1] results in a splat [2].
The root cause is the kfree_scale_thread thread(s) continue running
after unloading the rcuscale module. This commit fixes that isue by
invoking kfree_scale_cleanup() from rcu_scale_cleanup() when removing
the rcuscale module.
[1] modprobe rcuscale kfree_rcu_test=1
// After some time
rmmod rcuscale
rmmod torture
[2] BUG: unable to handle page fault for address: ffffffffc0601a87
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 11de4f067 P4D 11de4f067 PUD 11de51067 PMD 112f4d067 PTE 0
Oops: 0010 [#1] PREEMPT SMP NOPTI
CPU: 1 PID: 1798 Comm: kfree_scale_thr Not tainted 6.3.0-rc1-rcu+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015
RIP: 0010:0xffffffffc0601a87
Code: Unable to access opcode bytes at 0xffffffffc0601a5d.
RSP: 0018:ffffb25bc2e57e18 EFLAGS: 00010297
RAX: 0000000000000000 RBX: ffffffffc061f0b6 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff962fd0de RDI: ffffffff962fd0de
RBP: ffffb25bc2e57ea8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000000 R14: 000000000000000a R15: 00000000001c1dbe
FS: 0000000000000000(0000) GS:ffff921fa2200000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffc0601a5d CR3: 000000011de4c006 CR4: 0000000000370ee0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
? kvfree_call_rcu+0xf0/0x3a0
? kthread+0xf3/0x120
? kthread_complete_and_exit+0x20/0x20
? ret_from_fork+0x1f/0x30
</TASK>
Modules linked in: rfkill sunrpc ... [last unloaded: torture]
CR2: ffffffffc0601a87
---[ end trace 0000000000000000 ]---
Fixes: e6e78b004fa7 ("rcuperf: Add kfree_rcu() performance Tests")
Reviewed-by: Davidlohr Bueso <[email protected]>
Reviewed-by: Joel Fernandes (Google) <[email protected]>
Signed-off-by: Qiuxu Zhuo <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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This code-movement-only commit moves the rcu_scale_cleanup() and
rcu_scale_shutdown() functions to follow kfree_scale_cleanup().
This is code movement is in preparation for a bug-fix patch that invokes
kfree_scale_cleanup() from rcu_scale_cleanup().
Signed-off-by: Qiuxu Zhuo <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
Reviewed-by: Joel Fernandes (Google) <[email protected]>
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This commit adds a long_hold module parameter to allow testing diagnostics
for excessive lock-hold times. Also adjust torture_param() invocations
for longer line length while in the area.
Signed-off-by: Paul E. McKenney <[email protected]>
Reviewed-by: Joel Fernandes (Google) <[email protected]>
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Callbacks can only be queued as lazy on NOCB CPUs, therefore iterating
over the NOCB mask is enough for both counting and scanning. Just lock
the mostly uncontended barrier mutex on counting as well in order to
keep rcu_nocb_mask stable.
Signed-off-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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The rcu_tasks_invoke_cbs() function relies on queue_work_on() to silently
fall back to WORK_CPU_UNBOUND when the specified CPU is offline. However,
the queue_work_on() function's silent fallback mechanism relies on that
CPU having been online at some time in the past. When queue_work_on()
is passed a CPU that has never been online, workqueue lockups ensue,
which can be bad for your kernel's general health and well-being.
This commit therefore checks whether a given CPU has ever been online,
and, if not substitutes WORK_CPU_UNBOUND in the subsequent call to
queue_work_on(). Why not simply omit the queue_work_on() call entirely?
Because this function is flooding callback-invocation notifications
to all CPUs, and must deal with possibilities that include a sparse
cpu_possible_mask.
This commit also moves the setting of the rcu_data structure's
->beenonline field to rcu_cpu_starting(), which executes on the
incoming CPU before that CPU has ever enabled interrupts. This ensures
that the required workqueues are present. In addition, because the
incoming CPU has not yet enabled its interrupts, there cannot yet have
been any softirq handlers running on this CPU, which means that the
WARN_ON_ONCE(!rdp->beenonline) within the RCU_SOFTIRQ handler cannot
have triggered yet.
Fixes: d363f833c6d88 ("rcu-tasks: Use workqueues for multiple rcu_tasks_invoke_cbs() invocations")
Reported-by: Tejun Heo <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Currently, rcu_cpu_starting() is written so that it might be invoked
with interrupts enabled. However, it is always called when interrupts
are disabled, either by rcu_init(), notify_cpu_starting(), or from a
call point prior to the call to notify_cpu_starting().
But why bother requiring that interrupts be disabled? The purpose is
to allow the rcu_data structure's ->beenonline flag to be set after all
early processing has completed for the incoming CPU, thus allowing this
flag to be used to determine when workqueues have been set up for the
incoming CPU, while still allowing this flag to be used as a diagnostic
within rcu_core().
This commit therefore makes rcu_cpu_starting() rely on interrupts being
disabled.
Signed-off-by: Paul E. McKenney <[email protected]>
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The rcu_data structure's ->rcu_cpu_has_work field can be modified by
any CPU attempting to wake up the rcuc kthread. Therefore, this commit
marks accesses to this field from the rcu_cpu_kthread() function.
This data race was reported by KCSAN. Not appropriate for backporting
due to failure being unlikely.
Signed-off-by: Paul E. McKenney <[email protected]>
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The per-CPU rcu_data structure's ->cpu_no_qs.b.exp field is updated
only on the instance corresponding to the current CPU, but can be read
more widely. Unmarked accesses are OK from the corresponding CPU, but
only if interrupts are disabled, given that interrupt handlers can and
do modify this field.
Unfortunately, although the load from rcu_preempt_deferred_qs() is always
carried out from the corresponding CPU, interrupts are not necessarily
disabled. This commit therefore upgrades this load to READ_ONCE.
Similarly, the diagnostic access from synchronize_rcu_expedited_wait()
might run with interrupts disabled and from some other CPU. This commit
therefore marks this load with data_race().
Finally, the C-language access in rcu_preempt_ctxt_queue() is OK as
is because interrupts are disabled and this load is always from the
corresponding CPU. This commit adds a comment giving the rationale for
this access being safe.
This data race was reported by KCSAN. Not appropriate for backporting
due to failure being unlikely.
Signed-off-by: Paul E. McKenney <[email protected]>
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Currently, if there are more than 100 ready-to-invoke RCU callbacks queued
on a given CPU, the rcu_do_batch() function sets a timeout for invocation
of the series. This timeout defaulting to three milliseconds, and may
be adjusted using the rcutree.rcu_resched_ns kernel boot parameter.
This timeout is checked using local_clock(), but the overhead of this
function combined with the common-case very small callback-invocation
overhead means that local_clock() is checked every 32nd invocation.
This works well except for longer-than average callbacks. For example,
a series of 500-microsecond-duration callbacks means that local_clock()
is checked only once every 16 milliseconds, which makes it difficult to
enforce a three-millisecond timeout.
This commit therefore adds a Kconfig option RCU_DOUBLE_CHECK_CB_TIME
that enables backup timeout checking using the coarser grained but
lighter weight jiffies. If the jiffies counter detects a timeout,
then local_clock() is consulted even if this is not the 32nd callback.
This prevents the aforementioned 16-millisecond latency blow.
Reported-by: Domas Mituzas <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Currently, a callback-invocation time limit is enforced only for
callbacks invoked from the softirq environment, the rationale being
that when callbacks are instead invoked from rcuc and rcuoc kthreads,
these callbacks cannot be holding up other softirq vectors.
Which is in fact true. However, if an rcuc kthread spends too much time
invoking callbacks, it can delay quiescent-state reports from its CPU,
which can also be a problem.
This commit therefore applies the callback-invocation time limit to
callback invocation from the rcuc kthreads as well as from softirq.
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit uses rtp->name instead of __func__ and outputs the value
of rcu_task_cb_adjust, thus reducing console-log output.
Signed-off-by: Zqiang <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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pr_info() is called with rtp->cbs_gbl_lock spin lock locked. Because
pr_info() calls printk() that might sleep, this will result in BUG
like below:
[ 0.206455] cblist_init_generic: Setting adjustable number of callback queues.
[ 0.206463]
[ 0.206464] =============================
[ 0.206464] [ BUG: Invalid wait context ]
[ 0.206465] 5.19.0-00428-g9de1f9c8ca51 #5 Not tainted
[ 0.206466] -----------------------------
[ 0.206466] swapper/0/1 is trying to lock:
[ 0.206467] ffffffffa0167a58 (&port_lock_key){....}-{3:3}, at: serial8250_console_write+0x327/0x4a0
[ 0.206473] other info that might help us debug this:
[ 0.206473] context-{5:5}
[ 0.206474] 3 locks held by swapper/0/1:
[ 0.206474] #0: ffffffff9eb597e0 (rcu_tasks.cbs_gbl_lock){....}-{2:2}, at: cblist_init_generic.constprop.0+0x14/0x1f0
[ 0.206478] #1: ffffffff9eb579c0 (console_lock){+.+.}-{0:0}, at: _printk+0x63/0x7e
[ 0.206482] #2: ffffffff9ea77780 (console_owner){....}-{0:0}, at: console_emit_next_record.constprop.0+0x111/0x330
[ 0.206485] stack backtrace:
[ 0.206486] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.19.0-00428-g9de1f9c8ca51 #5
[ 0.206488] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-1.fc36 04/01/2014
[ 0.206489] Call Trace:
[ 0.206490] <TASK>
[ 0.206491] dump_stack_lvl+0x6a/0x9f
[ 0.206493] __lock_acquire.cold+0x2d7/0x2fe
[ 0.206496] ? stack_trace_save+0x46/0x70
[ 0.206497] lock_acquire+0xd1/0x2f0
[ 0.206499] ? serial8250_console_write+0x327/0x4a0
[ 0.206500] ? __lock_acquire+0x5c7/0x2720
[ 0.206502] _raw_spin_lock_irqsave+0x3d/0x90
[ 0.206504] ? serial8250_console_write+0x327/0x4a0
[ 0.206506] serial8250_console_write+0x327/0x4a0
[ 0.206508] console_emit_next_record.constprop.0+0x180/0x330
[ 0.206511] console_unlock+0xf7/0x1f0
[ 0.206512] vprintk_emit+0xf7/0x330
[ 0.206514] _printk+0x63/0x7e
[ 0.206516] cblist_init_generic.constprop.0.cold+0x24/0x32
[ 0.206518] rcu_init_tasks_generic+0x5/0xd9
[ 0.206522] kernel_init_freeable+0x15b/0x2a2
[ 0.206523] ? rest_init+0x160/0x160
[ 0.206526] kernel_init+0x11/0x120
[ 0.206527] ret_from_fork+0x1f/0x30
[ 0.206530] </TASK>
[ 0.207018] cblist_init_generic: Setting shift to 1 and lim to 1.
This patch moves pr_info() so that it is called without
rtp->cbs_gbl_lock locked.
Signed-off-by: Shigeru Yoshida <[email protected]>
Tested-by: "Zhang, Qiang1" <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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The ->lazy_len is only checked locklessly. Recheck again under the
->nocb_lock to avoid spending more time on flushing/waking if not
necessary. The ->lazy_len can still increment concurrently (from 1 to
infinity) but under the ->nocb_lock we at least know for sure if there
are lazy callbacks at all (->lazy_len > 0).
Signed-off-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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The shrinker resets the lazy callbacks counter in order to trigger the
pending lazy queue flush though the rcuog kthread. The counter reset is
protected by the ->nocb_lock against concurrent accesses...except
for one of them. Here is a list of existing synchronized readers/writer:
1) The first lazy enqueuer (incrementing ->lazy_len to 1) does so under
->nocb_lock and ->nocb_bypass_lock.
2) The further lazy enqueuers (incrementing ->lazy_len above 1) do so
under ->nocb_bypass_lock _only_.
3) The lazy flush checks and resets to 0 under ->nocb_lock and
->nocb_bypass_lock.
The shrinker protects its ->lazy_len reset against cases 1) and 3) but
not against 2). As such, setting ->lazy_len to 0 under the ->nocb_lock
may be cancelled right away by an overwrite from an enqueuer, leading
rcuog to ignore the flush.
To avoid that, use the proper bypass flush API which takes care of all
those details.
Signed-off-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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The shrinker may run concurrently with callbacks (de-)offloading. As
such, calling rcu_nocb_lock() is very dangerous because it does a
conditional locking. The worst outcome is that rcu_nocb_lock() doesn't
lock but rcu_nocb_unlock() eventually unlocks, or the reverse, creating
an imbalance.
Fix this with protecting against (de-)offloading using the barrier mutex.
Although if the barrier mutex is contended, which should be rare, then
step aside so as not to trigger a mutex VS allocation
dependency chain.
Signed-off-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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If the rcutree.rcu_min_cached_objs kernel boot parameter is set to zero,
then krcp->page_cache_work will never be triggered to fill page cache.
In addition, the put_cached_bnode() will not fill page cache. As a
result krcp->bkvcache will always be empty, so there is no need to acquire
krcp->lock to get page from krcp->bkvcache. This commit therefore makes
drain_page_cache() return immediately if the rcu_min_cached_objs is zero.
Signed-off-by: Zqiang <[email protected]>
Reviewed-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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When the fill_page_cache_func() function is invoked, it assumes that
the cache of pages is completely empty. However, there can be some time
between triggering execution of this function and its actual invocation.
During this time, kfree_rcu_work() might run, and might fill in part or
all of this cache of pages, thus invalidating the fill_page_cache_func()
function's assumption.
This will not overfill the cache because put_cached_bnode() will reject
the extra page. However, it will result in a needless allocation and
freeing of one extra page, which might not be helpful under lowish-memory
conditions.
This commit therefore causes the fill_page_cache_func() to explicitly
account for pages that have been placed into the cache shortly before
it starts running.
Signed-off-by: Zqiang <[email protected]>
Reviewed-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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By default the cache size is 5 pages per CPU, but it can be disabled at
boot time by setting the rcu_min_cached_objs to zero. When that happens,
the current code will uselessly set an hrtimer to schedule refilling this
cache with zero pages. This commit therefore streamlines this process
by simply refusing the set the hrtimer when rcu_min_cached_objs is zero.
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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The add_ptr_to_bulk_krc_lock() function is invoked to allocate a new
kfree_rcu() page, also known as a kvfree_rcu_bulk_data structure.
The kfree_rcu_cpu structure's lock is used to protect this operation,
except that this lock must be momentarily dropped when allocating memory.
It is clearly important that the lock that is reacquired be the same
lock that was acquired initially via krc_this_cpu_lock().
Unfortunately, this same krc_this_cpu_lock() function is used to
re-acquire this lock, and if the task migrated to some other CPU during
the memory allocation, this will result in the kvfree_rcu_bulk_data
structure being added to the wrong CPU's kfree_rcu_cpu structure.
This commit therefore replaces that second call to krc_this_cpu_lock()
with raw_spin_lock_irqsave() in order to explicitly acquire the lock on
the correct kfree_rcu_cpu structure, thus keeping things straight even
when the task migrates.
Signed-off-by: Zqiang <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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If kvfree_rcu_bulk() sees that the required grace period has failed to
elapse, it leaks the memory because readers might still be using it.
But in that case, the debug-objects subsystem still marks the relevant
structures as having been freed, even though they are instead being
leaked.
This commit fixes this mismatch by invoking debug_rcu_bhead_unqueue()
only when we are actually going to free the objects.
Signed-off-by: Zqiang <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Under low-memory conditions, kvfree_rcu() will use each object's
rcu_head structure to queue objects in a singly linked list headed by
the kfree_rcu_cpu structure's ->head field. This list is passed to
call_rcu() as a unit, but there is no indication of which grace period
this list needs to wait for. This in turn prevents adding debug checks
in the kfree_rcu_work() as was done for the two page-of-pointers channels
in the kfree_rcu_cpu structure.
This commit therefore adds a ->head_free_gp_snap field to the
kfree_rcu_cpu_work structure to record this grace-period number. It also
adds a WARN_ON_ONCE() to kfree_rcu_monitor() that checks to make sure
that the required grace period has in fact elapsed.
[ paulmck: Fix kerneldoc issue raised by Stephen Rothwell. ]
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit adds debugging checks to verify that the required RCU
grace period has elapsed for each kvfree_rcu_bulk_data structure that
arrives at the kvfree_rcu_bulk() function. These checks make use
of that structure's ->gp_snap field, which has been upgraded from an
unsigned long to an rcu_gp_oldstate structure. This upgrade reduces
the chances of false positives to nearly zero, even on 32-bit systems,
for which this structure carries 64 bits of state.
Cc: Ziwei Dai <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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This reverts the following commits:
4cd13c21b207 ("softirq: Let ksoftirqd do its job")
3c53776e29f8 ("Mark HI and TASKLET softirq synchronous")
1342d8080f61 ("softirq: Don't skip softirq execution when softirq thread is parking")
in a single change to avoid known bad intermediate states introduced by a
patch series reverting them individually.
Due to the mentioned commit, when the ksoftirqd threads take charge of
softirq processing, the system can experience high latencies.
In the past a few workarounds have been implemented for specific
side-effects of the initial ksoftirqd enforcement commit:
commit 1ff688209e2e ("watchdog: core: make sure the watchdog_worker is not deferred")
commit 8d5755b3f77b ("watchdog: softdog: fire watchdog even if softirqs do not get to run")
commit 217f69743681 ("net: busy-poll: allow preemption in sk_busy_loop()")
commit 3c53776e29f8 ("Mark HI and TASKLET softirq synchronous")
But the latency problem still exists in real-life workloads, see the link
below.
The reverted commit intended to solve a live-lock scenario that can now be
addressed with the NAPI threaded mode, introduced with commit 29863d41bb6e
("net: implement threaded-able napi poll loop support"), which is nowadays
in a pretty stable status.
While a complete solution to put softirq processing under nice resource
control would be preferable, that has proven to be a very hard task. In
the short term, remove the main pain point, and also simplify a bit the
current softirq implementation.
Signed-off-by: Paolo Abeni <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Jason Xing <[email protected]>
Reviewed-by: Jakub Kicinski <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Reviewed-by: Sebastian Andrzej Siewior <[email protected]>
Cc: "Paul E. McKenney" <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/netdev/[email protected]
Link: https://lore.kernel.org/r/57e66b364f1b6f09c9bc0316742c3b14f4ce83bd.1683526542.git.pabeni@redhat.com
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The current queue_work_on() docbook comment says that the caller must
ensure that the specified CPU can't go away, and further says that the
penalty for failing to nail down the specified CPU is that the workqueue
handler might find itself executing on some other CPU. This is true
as far as it goes, but fails to note what happens if the specified CPU
never was online. Therefore, further expand this comment to say that
specifying a CPU that was never online will result in a splat.
Signed-off-by: Paul E. McKenney <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Tejun Heo <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>
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cpuset_can_attach() can fail. Postpone DL BW allocation until all tasks
have been checked. DL BW is not allocated per-task but as a sum over
all DL tasks migrating.
If multiple controllers are attached to the cgroup next to the cpuset
controller a non-cpuset can_attach() can fail. In this case free DL BW
in cpuset_cancel_attach().
Finally, update cpuset DL task count (nr_deadline_tasks) only in
cpuset_attach().
Suggested-by: Waiman Long <[email protected]>
Signed-off-by: Dietmar Eggemann <[email protected]>
Signed-off-by: Juri Lelli <[email protected]>
Reviewed-by: Waiman Long <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>
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While moving a set of tasks between exclusive cpusets,
cpuset_can_attach() -> task_can_attach() calls dl_cpu_busy(..., p) for
DL BW overflow checking and per-task DL BW allocation on the destination
root_domain for the DL tasks in this set.
This approach has the issue of not freeing already allocated DL BW in
the following error cases:
(1) The set of tasks includes multiple DL tasks and DL BW overflow
checking fails for one of the subsequent DL tasks.
(2) Another controller next to the cpuset controller which is attached
to the same cgroup fails in its can_attach().
To address this problem rework dl_cpu_busy():
(1) Split it into dl_bw_check_overflow() & dl_bw_alloc() and add a
dedicated dl_bw_free().
(2) dl_bw_alloc() & dl_bw_free() take a `u64 dl_bw` parameter instead of
a `struct task_struct *p` used in dl_cpu_busy(). This allows to
allocate DL BW for a set of tasks too rather than only for a single
task.
Signed-off-by: Dietmar Eggemann <[email protected]>
Signed-off-by: Juri Lelli <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>
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