| Age | Commit message (Collapse) | Author | Files | Lines |
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If another lockdep report runs concurrently with an RCU lockdep report
from RCU_LOCKDEP_WARN(), the following sequence of events can occur:
1. debug_lockdep_rcu_enabled() sees that lockdep is enabled
when called from (say) synchronize_rcu().
2. Lockdep is disabled by a concurrent lockdep report.
3. debug_lockdep_rcu_enabled() evaluates its lockdep-expression
argument, for example, lock_is_held(&rcu_bh_lock_map).
4. Because lockdep is now disabled, lock_is_held() plays it safe and
returns the constant 1.
5. But in this case, the constant 1 is not safe, because invoking
synchronize_rcu() under rcu_read_lock_bh() is disallowed.
6. debug_lockdep_rcu_enabled() wrongly invokes lockdep_rcu_suspicious(),
resulting in a false-positive splat.
This commit therefore changes RCU_LOCKDEP_WARN() to check
debug_lockdep_rcu_enabled() after checking the lockdep expression,
so that any "safe" returns from lock_is_held() are rejected by
debug_lockdep_rcu_enabled(). This requires memory ordering, which is
supplied by READ_ONCE(debug_locks). The resulting volatile accesses
prevent the compiler from reordering and the fact that only one variable
is being accessed prevents the underlying hardware from reordering.
The combination works for IA64, which can reorder reads to the same
location, but this is defeated by the volatile accesses, which compile
to load instructions that provide ordering.
Reported-by: [email protected]
Reported-by: Matthew Wilcox <[email protected]>
Reported-by: [email protected]
Reported-by: Thomas Gleixner <[email protected]>
Suggested-by: Boqun Feng <[email protected]>
Reviewed-by: Boqun Feng <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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The reason that lockdep_rcu_suspicious() prints the value of debug_locks
is because a value of zero indicates a likely false positive. This can
work, but is a bit obtuse. This commit therefore explicitly calls out
the possibility of a false positive.
Reviewed-by: Boqun Feng <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit adds ->gp_max to show_rcu_gp_kthreads() output in order to
better diagnose RCU priority boosting failures.
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit adds ->rt_priority and ->gp_start to show_rcu_gp_kthreads()
output in order to better diagnose RCU priority boosting failures.
Signed-off-by: Paul E. McKenney <[email protected]>
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Currently, rcu_spawn_core_kthreads() is invoked via an early_initcall(),
which works, except that rcu_spawn_gp_kthread() is also invoked via an
early_initcall() and rcu_spawn_core_kthreads() relies on adjustments to
kthread_prio that are carried out by rcu_spawn_gp_kthread(). There is
no guaranttee of ordering among early_initcall() handlers, and thus no
guarantee that kthread_prio will be properly checked and range-limited
at the time that rcu_spawn_core_kthreads() needs it.
In most cases, this bug is harmless. After all, the only reason that
rcu_spawn_gp_kthread() adjusts the value of kthread_prio is if the user
specified a nonsensical value for this boot parameter, which experience
indicates is rare.
Nevertheless, a bug is a bug. This commit therefore causes the
rcu_spawn_core_kthreads() function to be invoked directly from
rcu_spawn_gp_kthread() after any needed adjustments to kthread_prio have
been carried out.
Fixes: 48d07c04b4cc ("rcu: Enable elimination of Tree-RCU softirq processing")
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit cleans up some comments and code in kernel/rcu/tree.c.
Signed-off-by: Zhouyi Zhou <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Commit 9ee01e0f69a9 ("x86/entry: Clean up idtentry_enter/exit()
leftovers") left the rcu_irq_exit_preempt() in place in order to avoid
conflicts with the -rcu tree. Now that this change has long since hit
mainline, this commit removes the no-longer-used rcu_irq_exit_preempt()
function.
Signed-off-by: Paul E. McKenney <[email protected]>
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func_states_equal makes a very short lived allocation for idmap,
probably because it's too large to fit on the stack. However the
function is called quite often, leading to a lot of alloc / free
churn. Replace the temporary allocation with dedicated scratch
space in struct bpf_verifier_env.
Signed-off-by: Lorenz Bauer <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Acked-by: Edward Cree <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
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Eliminate a couple needless kfree / kmalloc cycles by using
copy_array for jmp_history.
Signed-off-by: Lorenz Bauer <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
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Resizing and copying stack and reference tracking state currently
does a lot of kfree / kmalloc when the size of the tracked set changes.
The logic in copy_*_state and realloc_*_state is also hard to follow.
Refactor this into two core functions. copy_array copies from a source
into a destination. It avoids reallocation by taking the allocated
size of the destination into account via ksize(). The function is
essentially krealloc_array, with the difference that the contents of
dst are not preserved. realloc_array changes the size of an array and
zeroes newly allocated items. Contrary to krealloc both functions don't
free the destination if the size is zero. Instead we rely on free_func_state
to clean up.
realloc_stack_state is renamed to grow_stack_state to better convey
that it never shrinks the stack state.
Signed-off-by: Lorenz Bauer <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
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To make the purpose of the code more apparent, this commit moves the
tests of mem_dump_obj() to a new rcu_torture_mem_dump_obj() function
and calls it from rcu_torture_cleanup().
Signed-off-by: Paul E. McKenney <[email protected]>
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It will frequently be the case that rcu_torture_boost() will get a
->start_gp_poll() cookie that needs almost all of the current grace period
plus an additional grace period to elapse before ->poll_gp_state() will
return true. It is quite possible that the current grace period will have
(say) two seconds of stall by a CPU failing to pass through a quiescent
state, followed by 300 milliseconds of delay due to a preempted reader.
The next grace period might suffer only one second of stall by a CPU,
followed by another 300 milliseconds of delay due to a preempted reader.
This is an example of RCU priority boosting doing its job, but the full
elapsed time of 3.6 seconds exceeds the 3.5-second limit. In addition,
there is no CPU stall in force at the 3.5-second mark, so this would
nevertheless currently be counted as an RCU priority boosting failure.
This commit therefore avoids this sort of false positive by resetting
the gp_state_time timestamp any time that the current grace period is
being blocked by a CPU. This results in extremely frequent calls to
the ->check_boost_failed() function, so this commit provides a lockless
fastpath that is selected by supplying a NULL CPU-number pointer.
Signed-off-by: Paul E. McKenney <[email protected]>
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Currently, rcu_torture_boost() runs CPU-bound at real-time priority
to force RCU priority inversions. It then checks that grace periods
progress during this CPU-bound time. If grace periods fail to progress,
it reports and RCU priority boosting failure.
However, it is possible (and sometimes does happen) that the grace period
fails to progress due to a CPU failing to pass through a quiescent state
for an extended time period (3.5 seconds by default). This can happen
due to vCPU preemption, long-running interrupts, and much else besides.
There is nothing that RCU priority boosting can do about these situations,
and so they should not be counted as RCU priority boosting failures.
This commit therefore checks for CPUs (as opposed to preempted tasks)
holding up a grace period, and flags the resulting RCU priority boosting
failures, but does not splat nor count them as errors. It does rate-limit
them to avoid flooding the console log.
Signed-off-by: Paul E. McKenney <[email protected]>
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It is possible that a delayed grace period that rcu_torture_boost()
was polling for ended while rcu_torture_boost_failed() was printing the
failure splat. It would be good to know when this happens. This commit
therefore has rcu_torture_boost_failed() recheck the grace period after
printing the splat, and printing a message indicating whether or not
the grace period has ended.
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit consolidates two loops in rcu_torture_boost(), one of which
counts the number of boost-test episodes and the other of which computes
the start time of the next episode, into one loop that does both with but
a single acquisition of boost_mutex. This means that the count of the
number of boost-test episodes is incremented after an episode completes
rather than before it starts, but it also avoids the over-counting that
was possible previously.
Signed-off-by: Paul E. McKenney <[email protected]>
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If an rcu_torture_boost() kthread determines that its grace period
has not yet ended, it invokes rcu_torture_boost_failed() which checks
whether enough time has elapsed for this to be considered a failure of
RCU priority boosting, and, if so, flags the error.
Unfortunately, that kthread might be preempted for some seconds between
the time that it checks the grace period and the time that it checks the
time. This delay can result in a false positive, featuring a complaint
that a particular grace period has not ended, followed by a diagnostic
dump featuring a much later grace period.
This commit avoids these false positives by rechecking for the end of
the grace period after the time check.
Signed-off-by: Paul E. McKenney <[email protected]>
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Currently, rcutorture's testing of RCU priority boosting insists not
only that grace periods complete, but also that callbacks be invoked.
Although this is in fact what the user would want, ensuring that there
is sufficient CPU bandwidth devoted to callback execution is in fact
the user's responsibility. One could argue that rcutorture can take on
that responsibility, which is true in theory. But in practice, ensuring
sufficient CPU bandwidth to ksoftirqd, any rcuc kthreads, and any rcuo
kthreads is not particularly consistent with rcutorture's main job,
that of stress-testing RCU. In addition, if the system administrator
(say) makes very poor choices when pinning rcuo kthreads and then runs
rcutorture, there really isn't much rcutorture can do.
Besides, RCU priority boosting only boosts lagging readers, not all the
machinery required to invoke callbacks in a timely fashion.
This commit therefore switches rcutorture's evaluation of RCU priority
boosting from callback execution to grace-period completion by using
the new start_poll_synchronize_rcu() and poll_state_synchronize_rcu()
functions. When rcutorture is built in (as in when there is no innocent
workload to inconvenience), the ksoftirqd ktheads are boosted to real-time
priority 2 in order to allow timeouts to work properly in the face of
rcutorture's testing of RCU priority boosting.
Indeed, it is not as easy as it looks to create a reliable test of RCU
priority boosting without destroying the rest of the kernel!
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit adds a (*readlock_held)() function pointer to the
rcu_torture_ops structure in order to make the rcu_torture_one_read()
function's rcu_dereference_check() lockdep expression more appropriate
for a given run.
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit adds scale_type of acqrel, lock, and lock-irq to
test acquisition and release. Note that the refscale.nreaders=1
module parameter is required if you wish to test uncontended locking.
In contrast, acqrel uses a per-CPU variable, so should be just fine with
large values of the refscale.nreaders=1 module parameter.
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit adds a block comment that gives a high-level overview of
how RCU Rude grace periods progress. It also gives an overview of the
memory ordering.
Signed-off-by: Paul E. McKenney <[email protected]>
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This commit adds a block comment that gives a high-level overview of how
RCU tasks grace periods progress. It also adds a note about how exiting
tasks are handled, plus it gives an overview of the memory ordering.
Signed-off-by: Paul E. McKenney <[email protected]>
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An srcu_struct structure that is initialized before rcu_init_geometry()
will have its srcu_node hierarchy based on CONFIG_NR_CPUS. Once
rcu_init_geometry() is called, this hierarchy is compressed as needed
for the actual maximum number of CPUs for this system.
Later on, that srcu_struct structure is confused, sometimes referring
to its initial CONFIG_NR_CPUS-based hierarchy, and sometimes instead
to the new num_possible_cpus() hierarchy. For example, each of its
->mynode fields continues to reference the original leaf rcu_node
structures, some of which might no longer exist. On the other hand,
srcu_for_each_node_breadth_first() traverses to the new node hierarchy.
There are at least two bad possible outcomes to this:
1) a) A callback enqueued early on an srcu_data structure (call it
*sdp) is recorded pending on sdp->mynode->srcu_data_have_cbs in
srcu_funnel_gp_start() with sdp->mynode pointing to a deep leaf
(say 3 levels).
b) The grace period ends after rcu_init_geometry() shrinks the
nodes level to a single one. srcu_gp_end() walks through the new
srcu_node hierarchy without ever reaching the old leaves so the
callback is never executed.
This is easily reproduced on an 8 CPUs machine with CONFIG_NR_CPUS >= 32
and "rcupdate.rcu_self_test=1". The srcu_barrier() after early tests
verification never completes and the boot hangs:
[ 5413.141029] INFO: task swapper/0:1 blocked for more than 4915 seconds.
[ 5413.147564] Not tainted 5.12.0-rc4+ #28
[ 5413.151927] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 5413.159753] task:swapper/0 state:D stack: 0 pid: 1 ppid: 0 flags:0x00004000
[ 5413.168099] Call Trace:
[ 5413.170555] __schedule+0x36c/0x930
[ 5413.174057] ? wait_for_completion+0x88/0x110
[ 5413.178423] schedule+0x46/0xf0
[ 5413.181575] schedule_timeout+0x284/0x380
[ 5413.185591] ? wait_for_completion+0x88/0x110
[ 5413.189957] ? mark_held_locks+0x61/0x80
[ 5413.193882] ? mark_held_locks+0x61/0x80
[ 5413.197809] ? _raw_spin_unlock_irq+0x24/0x50
[ 5413.202173] ? wait_for_completion+0x88/0x110
[ 5413.206535] wait_for_completion+0xb4/0x110
[ 5413.210724] ? srcu_torture_stats_print+0x110/0x110
[ 5413.215610] srcu_barrier+0x187/0x200
[ 5413.219277] ? rcu_tasks_verify_self_tests+0x50/0x50
[ 5413.224244] ? rdinit_setup+0x2b/0x2b
[ 5413.227907] rcu_verify_early_boot_tests+0x2d/0x40
[ 5413.232700] do_one_initcall+0x63/0x310
[ 5413.236541] ? rdinit_setup+0x2b/0x2b
[ 5413.240207] ? rcu_read_lock_sched_held+0x52/0x80
[ 5413.244912] kernel_init_freeable+0x253/0x28f
[ 5413.249273] ? rest_init+0x250/0x250
[ 5413.252846] kernel_init+0xa/0x110
[ 5413.256257] ret_from_fork+0x22/0x30
2) An srcu_struct structure that is initialized before rcu_init_geometry()
and used afterward will always have stale rdp->mynode references,
resulting in callbacks to be missed in srcu_gp_end(), just like in
the previous scenario.
This commit therefore causes init_srcu_struct_nodes to initialize the
geometry, if needed. This ensures that the srcu_node hierarchy is
properly built and distributed from the get-go.
Suggested-by: Paul E. McKenney <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Once srcu_init() is called, the SRCU core will make use of delayed
workqueues, which rely on timers. However init_timers() is called
several steps after rcu_init(). This means that a call_srcu() after
rcu_init() but before init_timers() would find itself within a dangerously
uninitialized timer core.
This commit therefore creates a separate call to srcu_init() after
init_timer() completes, which ensures that we stay in early SRCU mode
until timers are safe(r).
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Joel Fernandes <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Pre-srcu_init() invocations of call_srcu() initialize the srcu_struct
structure in question, so there is no need to check this initialization
in srcu_init() when initiating grace periods for srcu_struct structures
that had early call_srcu() invocations. This commit therefore drops
the calls to check_init_srcu_struct() in srcu_init().
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Because alloc_percpu() zeroes out the allocated memory, there is no need
to zero-fill newly allocated per-CPU memory. This commit therefore removes
the loop zeroing the ->srcu_lock_count and ->srcu_unlock_count arrays
from init_srcu_struct_nodes(). This is the only use of that function's
is_static parameter, which this commit also removes.
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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This reverts commit dcd42591ebb8a25895b551a5297ea9c24414ba54.
The only user was RCU/nocb.
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Currently each CPU has its own ->nocb_timer queued when the nocb_gp
wakeup must be deferred. This approach has many drawbacks, compared to
a solution based on a single timer per NOCB group:
* There are a lot of timers to maintain.
* The per-rdp ->nocb_lock must be held to queue and cancel the timer
and this lock can already be heavily contended.
* One timer firing doesn't cancel the other timers in the same group:
- These other timers can thus cause spurious wakeups
- Each rdp that queued a timer must lock both ->nocb_lock and then
->nocb_gp_lock upon exit from the kernel to idle/user/guest mode.
* We can't cancel all of them if we detect an unflushed bypass in
nocb_gp_wait(). In fact currently we only ever cancel the ->nocb_timer
of the leader group.
* The leader group's nocb_timer is cancelled without locking ->nocb_lock
in nocb_gp_wait(). This currently appears to be safe but is an
accident waiting to happen.
* Since the timer acquires ->nocb_lock, it requires extra care in the
NOCB (de-)offloading process, requiring that it be either enabled or
disabled and then flushed.
This commit instead uses the rcuog kthread's CPU's ->nocb_timer instead.
It is protected by nocb_gp_lock, which is _way_ less contended and
remains so even after this change. As a matter of fact, the nocb_timer
almost never fires and the deferred wakeup is mostly carried out upon
idle/user/guest entry. Now the early check performed at this point in
do_nocb_deferred_wakeup() is done on rdp_gp->nocb_defer_wakeup, which
is of course racy. However, this raciness is harmless because we only
need the guarantee that the timer is queued if we were the last one to
queue it. Any other situation (another CPU has queued it and we either
see it or not) is fine.
This solves all the issues listed above.
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Lai Jiangshan <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Boqun Feng <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Currently we have three functions which depend on each other.
Two of them are quite tiny and the last one where the most
work is done. All of them are related to queuing RCU batches
to reclaim objects after a GP.
1. kfree_rcu_monitor(). It consist of few lines. It acquires a spin-lock
and calls kfree_rcu_drain_unlock().
2. kfree_rcu_drain_unlock(). It also consists of few lines of code. It
calls queue_kfree_rcu_work() to queue the batch. If this fails,
it rearms the monitor work to try again later.
3. queue_kfree_rcu_work(). This provides the bulk of the functionality,
attempting to start a new batch to free objects after a GP.
Since there are no external users of functions [2] and [3], both
can eliminated by moving all logic directly into [1], which both
shrinks and simplifies the code.
Also replace comments which start with "/*" to "//" format to make it
unified across the file.
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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The kvfree_rcu() function now defers allocations in the common
case due to the fact that there is no lockless access to the
memory-allocator caches/pools. In addition, in CONFIG_PREEMPT_NONE=y
and in CONFIG_PREEMPT_VOLUNTARY=y kernels, there is no reliable way to
determine if spinlocks are held. As a result, allocation is deferred in
the common case, and the two-argument form of kvfree_rcu() thus uses the
"channel 3" queue through all the rcu_head structures. This channel
is called referred to as the emergency case in comments, and these
comments are now obsolete.
This commit therefore updates these comments to reflect the new
common-case nature of such emergencies.
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Replace an open-coded version of the kfree_rcu_monitor() function body
with a call to that function.
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Before attempting to start a new batch the "monitor_todo" variable is
set to "false" and set back to "true" when a previous RCU batch is still
in progress. This is at best confusing.
Thus change this variable to "false" only when a new batch has been
successfully queued, otherwise, just leave it be.
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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The rcu_scheduler_active flag is set to RCU_SCHEDULER_RUNNING once the
scheduler is up and running. That signal is used in order to check
and queue a "monitor work" to reclaim freed objects (if there are any)
during early boot. This flag is used by kvfree_rcu() to determine when
work can safely be queued, at which point memory passed to earlier
invocations of kvfree_rcu() can be processed.
However, only "krcp->head" is checked for objects that need to be
released, and there are now two more, namely, "krcp->bkvhead[0]" and
"krcp->bkvhead[1]". Therefore, check these two additional channels.
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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nr_bkv_objs is a count of the objects in the kvfree_rcu page cache.
Accessing it requires holding the ->lock. Switch to READ_ONCE() and
WRITE_ONCE() macros to provide lockless access to this counter.
This lockless access is used for the shrinker.
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Add a drain_page_cache() function to drain a per-cpu page cache.
The reason behind of it is a system can run into a low memory
condition, in that case a page shrinker can ask for its users
to free their caches in order to get extra memory available for
other needs in a system.
When a system hits such condition, a page cache is drained for
all CPUs in a system. By default a page cache work is delayed
with 5 seconds interval until a memory pressure disappears, if
needed it can be changed. See a rcu_delay_page_cache_fill_msec
module parameter.
Co-developed-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Uladzislau Rezki (Sony) <[email protected]>
Signed-off-by: Zqiang <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Signed-off-by: Rolf Eike Beer <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Fix the following checkpatch warning in auditsc.c:
WARNING: Missing a blank line after declarations
Signed-off-by: Roni Nevalainen <[email protected]>
Signed-off-by: Paul Moore <[email protected]>
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The 'all' semantics is now supported by the bitmap_parselist() so we can
drop supporting it as a special case in RCU code. Since 'all' is properly
supported in core bitmap code, also drop legacy comment in RCU for it.
This patch does not make any functional changes for existing users.
Reviewed-by: Andy Shevchenko <[email protected]>
Signed-off-by: Yury Norov <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>
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Introduce the cgroup.kill file. It does what it says on the tin and
allows a caller to kill a cgroup by writing "1" into cgroup.kill.
The file is available in non-root cgroups.
Killing cgroups is a process directed operation, i.e. the whole
thread-group is affected. Consequently trying to write to cgroup.kill in
threaded cgroups will be rejected and EOPNOTSUPP returned. This behavior
aligns with cgroup.procs where reads in threaded-cgroups are rejected
with EOPNOTSUPP.
The cgroup.kill file is write-only since killing a cgroup is an event
not which makes it different from e.g. freezer where a cgroup
transitions between the two states.
As with all new cgroup features cgroup.kill is recursive by default.
Killing a cgroup is protected against concurrent migrations through the
cgroup mutex. To protect against forkbombs and to mitigate the effect of
racing forks a new CGRP_KILL css set lock protected flag is introduced
that is set prior to killing a cgroup and unset after the cgroup has
been killed. We can then check in cgroup_post_fork() where we hold the
css set lock already whether the cgroup is currently being killed. If so
we send the child a SIGKILL signal immediately taking it down as soon as
it returns to userspace. To make the killing of the child semantically
clean it is killed after all cgroup attachment operations have been
finalized.
There are various use-cases of this interface:
- Containers usually have a conservative layout where each container
usually has a delegated cgroup. For such layouts there is a 1:1
mapping between container and cgroup. If the container in addition
uses a separate pid namespace then killing a container usually becomes
a simple kill -9 <container-init-pid> from an ancestor pid namespace.
However, there are quite a few scenarios where that isn't true. For
example, there are containers that share the cgroup with other
processes on purpose that are supposed to be bound to the lifetime of
the container but are not in the same pidns of the container.
Containers that are in a delegated cgroup but share the pid namespace
with the host or other containers.
- Service managers such as systemd use cgroups to group and organize
processes belonging to a service. They usually rely on a recursive
algorithm now to kill a service. With cgroup.kill this becomes a
simple write to cgroup.kill.
- Userspace OOM implementations can make good use of this feature to
efficiently take down whole cgroups quickly.
- The kill program can gain a new
kill --cgroup /sys/fs/cgroup/delegated
flag to take down cgroups.
A few observations about the semantics:
- If parent and child are in the same cgroup and CLONE_INTO_CGROUP is
not specified we are not taking cgroup mutex meaning the cgroup can be
killed while a process in that cgroup is forking.
If the kill request happens right before cgroup_can_fork() and before
the parent grabs its siglock the parent is guaranteed to see the
pending SIGKILL. In addition we perform another check in
cgroup_post_fork() whether the cgroup is being killed and is so take
down the child (see above). This is robust enough and protects gainst
forkbombs. If userspace really really wants to have stricter
protection the simple solution would be to grab the write side of the
cgroup threadgroup rwsem which will force all ongoing forks to
complete before killing starts. We concluded that this is not
necessary as the semantics for concurrent forking should simply align
with freezer where a similar check as cgroup_post_fork() is performed.
For all other cases CLONE_INTO_CGROUP is required. In this case we
will grab the cgroup mutex so the cgroup can't be killed while we
fork. Once we're done with the fork and have dropped cgroup mutex we
are visible and will be found by any subsequent kill request.
- We obviously don't kill kthreads. This means a cgroup that has a
kthread will not become empty after killing and consequently no
unpopulated event will be generated. The assumption is that kthreads
should be in the root cgroup only anyway so this is not an issue.
- We skip killing tasks that already have pending fatal signals.
- Freezer doesn't care about tasks in different pid namespaces, i.e. if
you have two tasks in different pid namespaces the cgroup would still
be frozen. The cgroup.kill mechanism consequently behaves the same
way, i.e. we kill all processes and ignore in which pid namespace they
exist.
- If the caller is located in a cgroup that is killed the caller will
obviously be killed as well.
Link: https://lore.kernel.org/r/[email protected]
Cc: Shakeel Butt <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Tejun Heo <[email protected]>
Cc: [email protected]
Reviewed-by: Shakeel Butt <[email protected]>
Reviewed-by: Serge Hallyn <[email protected]>
Acked-by: Roman Gushchin <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>
Signed-off-by: Tejun Heo <[email protected]>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fixes from Thomas Gleixner:
"A set of scheduler updates:
- Prevent PSI state corruption when schedule() races with cgroup
move.
A recent commit combined two PSI callbacks to reduce the number of
cgroup tree updates, but missed that schedule() can drop rq::lock
for load balancing, which opens the race window for
cgroup_move_task() which then observes half updated state.
The fix is to solely use task::ps_flags instead of looking at the
potentially mismatching scheduler state
- Prevent an out-of-bounds access in uclamp caused bu a rounding
division which can lead to an off-by-one error exceeding the
buckets array size.
- Prevent unfairness caused by missing load decay when a task is
attached to a cfs runqueue.
The old load of the task was attached to the runqueue and never
removed. Fix it by enforcing the load update through the hierarchy
for unthrottled run queue instances.
- A documentation fix fot the 'sched_verbose' command line option"
* tag 'sched-urgent-2021-05-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched/fair: Fix unfairness caused by missing load decay
sched: Fix out-of-bound access in uclamp
psi: Fix psi state corruption when schedule() races with cgroup move
sched,doc: sched_debug_verbose cmdline should be sched_verbose
|
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Thomas Gleixner:
"A set of locking related fixes and updates:
- Two fixes for the futex syscall related to the timeout handling.
FUTEX_LOCK_PI does not support the FUTEX_CLOCK_REALTIME bit and
because it's not set the time namespace adjustment for clock
MONOTONIC is applied wrongly.
FUTEX_WAIT cannot support the FUTEX_CLOCK_REALTIME bit because its
always a relative timeout.
- Cleanups in the futex syscall entry points which became obvious
when the two timeout handling bugs were fixed.
- Cleanup of queued_write_lock_slowpath() as suggested by Linus
- Fixup of the smp_call_function_single_async() prototype"
* tag 'locking-urgent-2021-05-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
futex: Make syscall entry points less convoluted
futex: Get rid of the val2 conditional dance
futex: Do not apply time namespace adjustment on FUTEX_LOCK_PI
Revert 337f13046ff0 ("futex: Allow FUTEX_CLOCK_REALTIME with FUTEX_WAIT op")
locking/qrwlock: Cleanup queued_write_lock_slowpath()
smp: Fix smp_call_function_single_async prototype
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git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull more Kbuild updates from Masahiro Yamada:
- Convert sh and sparc to use generic shell scripts to generate the
syscall headers
- refactor .gitignore files
- Update kernel/config_data.gz only when the content of the .config
is really changed, which avoids the unneeded re-link of vmlinux
- move "remove stale files" workarounds to scripts/remove-stale-files
- suppress unused-but-set-variable warnings by default for Clang
as well
- fix locale setting LANG=C to LC_ALL=C
- improve 'make distclean'
- always keep intermediate objects from scripts/link-vmlinux.sh
- move IF_ENABLED out of <linux/kconfig.h> to make it self-contained
- misc cleanups
* tag 'kbuild-v5.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild: (25 commits)
linux/kconfig.h: replace IF_ENABLED() with PTR_IF() in <linux/kernel.h>
kbuild: Don't remove link-vmlinux temporary files on exit/signal
kbuild: remove the unneeded comments for external module builds
kbuild: make distclean remove tag files in sub-directories
kbuild: make distclean work against $(objtree) instead of $(srctree)
kbuild: refactor modname-multi by using suffix-search
kbuild: refactor fdtoverlay rule
kbuild: parameterize the .o part of suffix-search
arch: use cross_compiling to check whether it is a cross build or not
kbuild: remove ARCH=sh64 support from top Makefile
.gitignore: prefix local generated files with a slash
kbuild: replace LANG=C with LC_ALL=C
Makefile: Move -Wno-unused-but-set-variable out of GCC only block
kbuild: add a script to remove stale generated files
kbuild: update config_data.gz only when the content of .config is changed
.gitignore: ignore only top-level modules.builtin
.gitignore: move tags and TAGS close to other tag files
kernel/.gitgnore: remove stale timeconst.h and hz.bc
usr/include: refactor .gitignore
genksyms: fix stale comment
...
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git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
Pull networking fixes from Jakub Kicinski:
"Networking fixes for 5.13-rc1, including fixes from bpf, can and
netfilter trees. Self-contained fixes, nothing risky.
Current release - new code bugs:
- dsa: ksz: fix a few bugs found by static-checker in the new driver
- stmmac: fix frame preemption handshake not triggering after
interface restart
Previous releases - regressions:
- make nla_strcmp handle more then one trailing null character
- fix stack OOB reads while fragmenting IPv4 packets in openvswitch
and net/sched
- sctp: do asoc update earlier in sctp_sf_do_dupcook_a
- sctp: delay auto_asconf init until binding the first addr
- stmmac: clear receive all(RA) bit when promiscuous mode is off
- can: mcp251x: fix resume from sleep before interface was brought up
Previous releases - always broken:
- bpf: fix leakage of uninitialized bpf stack under speculation
- bpf: fix masking negation logic upon negative dst register
- netfilter: don't assume that skb_header_pointer() will never fail
- only allow init netns to set default tcp cong to a restricted algo
- xsk: fix xp_aligned_validate_desc() when len == chunk_size to avoid
false positive errors
- ethtool: fix missing NLM_F_MULTI flag when dumping
- can: m_can: m_can_tx_work_queue(): fix tx_skb race condition
- sctp: fix a SCTP_MIB_CURRESTAB leak in sctp_sf_do_dupcook_b
- bridge: fix NULL-deref caused by a races between assigning
rx_handler_data and setting the IFF_BRIDGE_PORT bit
Latecomer:
- seg6: add counters support for SRv6 Behaviors"
* tag 'net-5.13-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net: (73 commits)
atm: firestream: Use fallthrough pseudo-keyword
net: stmmac: Do not enable RX FIFO overflow interrupts
mptcp: fix splat when closing unaccepted socket
i40e: Remove LLDP frame filters
i40e: Fix PHY type identifiers for 2.5G and 5G adapters
i40e: fix the restart auto-negotiation after FEC modified
i40e: Fix use-after-free in i40e_client_subtask()
i40e: fix broken XDP support
netfilter: nftables: avoid potential overflows on 32bit arches
netfilter: nftables: avoid overflows in nft_hash_buckets()
tcp: Specify cmsgbuf is user pointer for receive zerocopy.
mlxsw: spectrum_mr: Update egress RIF list before route's action
net: ipa: fix inter-EE IRQ register definitions
can: m_can: m_can_tx_work_queue(): fix tx_skb race condition
can: mcp251x: fix resume from sleep before interface was brought up
can: mcp251xfd: mcp251xfd_probe(): add missing can_rx_offload_del() in error path
can: mcp251xfd: mcp251xfd_probe(): fix an error pointer dereference in probe
netfilter: nftables: Fix a memleak from userdata error path in new objects
netfilter: remove BUG_ON() after skb_header_pointer()
netfilter: nfnetlink_osf: Fix a missing skb_header_pointer() NULL check
...
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Merge yet more updates from Andrew Morton:
"This is everything else from -mm for this merge window.
90 patches.
Subsystems affected by this patch series: mm (cleanups and slub),
alpha, procfs, sysctl, misc, core-kernel, bitmap, lib, compat,
checkpatch, epoll, isofs, nilfs2, hpfs, exit, fork, kexec, gcov,
panic, delayacct, gdb, resource, selftests, async, initramfs, ipc,
drivers/char, and spelling"
* emailed patches from Andrew Morton <[email protected]>: (90 commits)
mm: fix typos in comments
mm: fix typos in comments
treewide: remove editor modelines and cruft
ipc/sem.c: spelling fix
fs: fat: fix spelling typo of values
kernel/sys.c: fix typo
kernel/up.c: fix typo
kernel/user_namespace.c: fix typos
kernel/umh.c: fix some spelling mistakes
include/linux/pgtable.h: few spelling fixes
mm/slab.c: fix spelling mistake "disired" -> "desired"
scripts/spelling.txt: add "overflw"
scripts/spelling.txt: Add "diabled" typo
scripts/spelling.txt: add "overlfow"
arm: print alloc free paths for address in registers
mm/vmalloc: remove vwrite()
mm: remove xlate_dev_kmem_ptr()
drivers/char: remove /dev/kmem for good
mm: fix some typos and code style problems
ipc/sem.c: mundane typo fixes
...
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change 'infite' to 'infinite'
change 'concurent' to 'concurrent'
change 'memvers' to 'members'
change 'decendants' to 'descendants'
change 'argumets' to 'arguments'
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Xiaofeng Cao <[email protected]>
Acked-by: Randy Dunlap <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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s/condtions/conditions/
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Bhaskar Chowdhury <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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change 'verifing' to 'verifying'
change 'certaint' to 'certain'
change 'approprpiate' to 'appropriate'
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Xiaofeng Cao <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Fix some spelling mistakes, and modify the order of the parameter comments
to be consistent with the order of the parameters passed to the function.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: zhouchuangao <[email protected]>
Acked-by: Luis Chamberlain <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Patch series "drivers/char: remove /dev/kmem for good".
Exploring /dev/kmem and /dev/mem in the context of memory hot(un)plug and
memory ballooning, I started questioning the existence of /dev/kmem.
Comparing it with the /proc/kcore implementation, it does not seem to be
able to deal with things like
a) Pages unmapped from the direct mapping (e.g., to be used by secretmem)
-> kern_addr_valid(). virt_addr_valid() is not sufficient.
b) Special cases like gart aperture memory that is not to be touched
-> mem_pfn_is_ram()
Unless I am missing something, it's at least broken in some cases and might
fault/crash the machine.
Looks like its existence has been questioned before in 2005 and 2010 [1],
after ~11 additional years, it might make sense to revive the discussion.
CONFIG_DEVKMEM is only enabled in a single defconfig (on purpose or by
mistake?). All distributions disable it: in Ubuntu it has been disabled
for more than 10 years, in Debian since 2.6.31, in Fedora at least
starting with FC3, in RHEL starting with RHEL4, in SUSE starting from
15sp2, and OpenSUSE has it disabled as well.
1) /dev/kmem was popular for rootkits [2] before it got disabled
basically everywhere. Ubuntu documents [3] "There is no modern user of
/dev/kmem any more beyond attackers using it to load kernel rootkits.".
RHEL documents in a BZ [5] "it served no practical purpose other than to
serve as a potential security problem or to enable binary module drivers
to access structures/functions they shouldn't be touching"
2) /proc/kcore is a decent interface to have a controlled way to read
kernel memory for debugging puposes. (will need some extensions to
deal with memory offlining/unplug, memory ballooning, and poisoned
pages, though)
3) It might be useful for corner case debugging [1]. KDB/KGDB might be a
better fit, especially, to write random memory; harder to shoot
yourself into the foot.
4) "Kernel Memory Editor" [4] hasn't seen any updates since 2000 and seems
to be incompatible with 64bit [1]. For educational purposes,
/proc/kcore might be used to monitor value updates -- or older
kernels can be used.
5) It's broken on arm64, and therefore, completely disabled there.
Looks like it's essentially unused and has been replaced by better
suited interfaces for individual tasks (/proc/kcore, KDB/KGDB). Let's
just remove it.
[1] https://lwn.net/Articles/147901/
[2] https://www.linuxjournal.com/article/10505
[3] https://wiki.ubuntu.com/Security/Features#A.2Fdev.2Fkmem_disabled
[4] https://sourceforge.net/projects/kme/
[5] https://bugzilla.redhat.com/show_bug.cgi?id=154796
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: David Hildenbrand <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Acked-by: Kees Cook <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: "Alexander A. Klimov" <[email protected]>
Cc: Alexander Viro <[email protected]>
Cc: Alexandre Belloni <[email protected]>
Cc: Andrew Lunn <[email protected]>
Cc: Andrey Zhizhikin <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Brian Cain <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: Christophe Leroy <[email protected]>
Cc: Chris Zankel <[email protected]>
Cc: Corentin Labbe <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: "Eric W. Biederman" <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: Gerald Schaefer <[email protected]>
Cc: Greentime Hu <[email protected]>
Cc: Gregory Clement <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: huang ying <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Ivan Kokshaysky <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: James Troup <[email protected]>
Cc: Jiaxun Yang <[email protected]>
Cc: Jonas Bonn <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Kairui Song <[email protected]>
Cc: Krzysztof Kozlowski <[email protected]>
Cc: Kuninori Morimoto <[email protected]>
Cc: Liviu Dudau <[email protected]>
Cc: Lorenzo Pieralisi <[email protected]>
Cc: Luc Van Oostenryck <[email protected]>
Cc: Luis Chamberlain <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Matt Turner <[email protected]>
Cc: Max Filippov <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Mikulas Patocka <[email protected]>
Cc: Minchan Kim <[email protected]>
Cc: Niklas Schnelle <[email protected]>
Cc: Oleksiy Avramchenko <[email protected]>
Cc: [email protected]
Cc: Palmer Dabbelt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: "Pavel Machek (CIP)" <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: "Peter Zijlstra (Intel)" <[email protected]>
Cc: Pierre Morel <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: Richard Henderson <[email protected]>
Cc: Rich Felker <[email protected]>
Cc: Robert Richter <[email protected]>
Cc: Rob Herring <[email protected]>
Cc: Russell King <[email protected]>
Cc: Sam Ravnborg <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Cc: Sebastian Hesselbarth <[email protected]>
Cc: [email protected]
Cc: Stafford Horne <[email protected]>
Cc: Stefan Kristiansson <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Sudeep Holla <[email protected]>
Cc: Theodore Dubois <[email protected]>
Cc: Thomas Bogendoerfer <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Viresh Kumar <[email protected]>
Cc: William Cohen <[email protected]>
Cc: Xiaoming Ni <[email protected]>
Cc: Yoshinori Sato <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Allow the developer to specifiy the initial value of the modprobe_path[]
string. This can be used to set it to the empty string initially, thus
effectively disabling request_module() during early boot until userspace
writes a new value via the /proc/sys/kernel/modprobe interface. [1]
When building a custom kernel (often for an embedded target), it's normal
to build everything into the kernel that is needed for booting, and indeed
the initramfs often contains no modules at all, so every such
request_module() done before userspace init has mounted the real rootfs is
a waste of time.
This is particularly useful when combined with the previous patch, which
made the initramfs unpacking asynchronous - for that to work, it had to
make any usermodehelper call wait for the unpacking to finish before
attempting to invoke the userspace helper. By eliminating all such
(known-to-be-futile) calls of usermodehelper, the initramfs unpacking and
the {device,late}_initcalls can proceed in parallel for much longer.
For a relatively slow ppc board I'm working on, the two patches combined
lead to 0.2s faster boot - but more importantly, the fact that the
initramfs unpacking proceeds completely in the background while devices
get probed means I get to handle the gpio watchdog in time without getting
reset.
[1] __request_module() already has an early -ENOENT return when
modprobe_path is the empty string.
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Rasmus Villemoes <[email protected]>
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Acked-by: Jessica Yu <[email protected]>
Acked-by: Luis Chamberlain <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Takashi Iwai <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
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Patch series "background initramfs unpacking, and CONFIG_MODPROBE_PATH", v3.
These two patches are independent, but better-together.
The second is a rather trivial patch that simply allows the developer to
change "/sbin/modprobe" to something else - e.g. the empty string, so
that all request_module() during early boot return -ENOENT early, without
even spawning a usermode helper, needlessly synchronizing with the
initramfs unpacking.
The first patch delegates decompressing the initramfs to a worker thread,
allowing do_initcalls() in main.c to proceed to the device_ and late_
initcalls without waiting for that decompression (and populating of
rootfs) to finish. Obviously, some of those later calls may rely on the
initramfs being available, so I've added synchronization points in the
firmware loader and usermodehelper paths - there might be other places
that would need this, but so far no one has been able to think of any
places I have missed.
There's not much to win if most of the functionality needed during boot is
only available as modules. But systems with a custom-made .config and
initramfs can boot faster, partly due to utilizing more than one cpu
earlier, partly by avoiding known-futile modprobe calls (which would still
trigger synchronization with the initramfs unpacking, thus eliminating
most of the first benefit).
This patch (of 2):
Most of the boot process doesn't actually need anything from the
initramfs, until of course PID1 is to be executed. So instead of doing
the decompressing and populating of the initramfs synchronously in
populate_rootfs() itself, push that off to a worker thread.
This is primarily motivated by an embedded ppc target, where unpacking
even the rather modest sized initramfs takes 0.6 seconds, which is long
enough that the external watchdog becomes unhappy that it doesn't get
attention soon enough. By doing the initramfs decompression in a worker
thread, we get to do the device_initcalls and hence start petting the
watchdog much sooner.
Normal desktops might benefit as well. On my mostly stock Ubuntu kernel,
my initramfs is a 26M xz-compressed blob, decompressing to around 126M.
That takes almost two seconds:
[ 0.201454] Trying to unpack rootfs image as initramfs...
[ 1.976633] Freeing initrd memory: 29416K
Before this patch, these lines occur consecutively in dmesg. With this
patch, the timestamps on these two lines is roughly the same as above, but
with 172 lines inbetween - so more than one cpu has been kept busy doing
work that would otherwise only happen after the populate_rootfs()
finished.
Should one of the initcalls done after rootfs_initcall time (i.e., device_
and late_ initcalls) need something from the initramfs (say, a kernel
module or a firmware blob), it will simply wait for the initramfs
unpacking to be done before proceeding, which should in theory make this
completely safe.
But if some driver pokes around in the filesystem directly and not via one
of the official kernel interfaces (i.e. request_firmware*(),
call_usermodehelper*) that theory may not hold - also, I certainly might
have missed a spot when sprinkling wait_for_initramfs(). So there is an
escape hatch in the form of an initramfs_async= command line parameter.
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Rasmus Villemoes <[email protected]>
Reviewed-by: Luis Chamberlain <[email protected]>
Cc: Jessica Yu <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jonathan Corbet <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Nick Desaulniers <[email protected]>
Cc: Takashi Iwai <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
|