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Added various checks on open tracefs calls to see if tracefs is in lockdown
mode, and if so, to return -EPERM.
Note, the event format files (which are basically standard on all machines)
as well as the enabled_functions file (which shows what is currently being
traced) are not lockde down. Perhaps they should be, but it seems counter
intuitive to lockdown information to help you know if the system has been
modified.
Link: http://lkml.kernel.org/r/CAHk-=wj7fGPKUspr579Cii-w_y60PtRaiDgKuxVtBAMK0VNNkA@mail.gmail.com
Suggested-by: Linus Torvalds <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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Currently, most files in the tracefs directory test if tracing_disabled is
set. If so, it should return -ENODEV. The tracing_disabled is called when
tracing is found to be broken. Originally it was done in case the ring
buffer was found to be corrupted, and we wanted to prevent reading it from
crashing the kernel. But it's also called if a tracing selftest fails on
boot. It's a one way switch. That is, once it is triggered, tracing is
disabled until reboot.
As most tracefs files can also be used by instances in the tracefs
directory, they need to be carefully done. Each instance has a trace_array
associated to it, and when the instance is removed, the trace_array is
freed. But if an instance is opened with a reference to the trace_array,
then it requires looking up the trace_array to get its ref counter (as there
could be a race with it being deleted and the open itself). Once it is
found, a reference is added to prevent the instance from being removed (and
the trace_array associated with it freed).
Combine the two checks (tracing_disabled and trace_array_get()) into a
single helper function. This will also make it easier to add lockdown to
tracefs later.
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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Original changelog from Steve Rostedt (except last sentence which
explains the problem, and the Fixes: tag):
I performed a three way histogram with the following commands:
echo 'irq_lat u64 lat pid_t pid' > synthetic_events
echo 'wake_lat u64 lat u64 irqlat pid_t pid' >> synthetic_events
echo 'hist:keys=common_pid:irqts=common_timestamp.usecs if function == 0xffffffff81200580' > events/timer/hrtimer_start/trigger
echo 'hist:keys=common_pid:lat=common_timestamp.usecs-$irqts:onmatch(timer.hrtimer_start).irq_lat($lat,pid) if common_flags & 1' > events/sched/sched_waking/trigger
echo 'hist:keys=pid:wakets=common_timestamp.usecs,irqlat=lat' > events/synthetic/irq_lat/trigger
echo 'hist:keys=next_pid:lat=common_timestamp.usecs-$wakets,irqlat=$irqlat:onmatch(synthetic.irq_lat).wake_lat($lat,$irqlat,next_pid)' > events/sched/sched_switch/trigger
echo 1 > events/synthetic/wake_lat/enable
Basically I wanted to see:
hrtimer_start (calling function tick_sched_timer)
Note:
# grep tick_sched_timer /proc/kallsyms
ffffffff81200580 t tick_sched_timer
And save the time of that, and then record sched_waking if it is called
in interrupt context and with the same pid as the hrtimer_start, it
will record the latency between that and the waking event.
I then look at when the task that is woken is scheduled in, and record
the latency between the wakeup and the task running.
At the end, the wake_lat synthetic event will show the wakeup to
scheduled latency, as well as the irq latency in from hritmer_start to
the wakeup. The problem is that I found this:
<idle>-0 [007] d... 190.485261: wake_lat: lat=27 irqlat=190485230 pid=698
<idle>-0 [005] d... 190.485283: wake_lat: lat=40 irqlat=190485239 pid=10
<idle>-0 [002] d... 190.488327: wake_lat: lat=56 irqlat=190488266 pid=335
<idle>-0 [005] d... 190.489330: wake_lat: lat=64 irqlat=190489262 pid=10
<idle>-0 [003] d... 190.490312: wake_lat: lat=43 irqlat=190490265 pid=77
<idle>-0 [005] d... 190.493322: wake_lat: lat=54 irqlat=190493262 pid=10
<idle>-0 [005] d... 190.497305: wake_lat: lat=35 irqlat=190497267 pid=10
<idle>-0 [005] d... 190.501319: wake_lat: lat=50 irqlat=190501264 pid=10
The irqlat seemed quite large! Investigating this further, if I had
enabled the irq_lat synthetic event, I noticed this:
<idle>-0 [002] d.s. 249.429308: irq_lat: lat=164968 pid=335
<idle>-0 [002] d... 249.429369: wake_lat: lat=55 irqlat=249429308 pid=335
Notice that the timestamp of the irq_lat "249.429308" is awfully
similar to the reported irqlat variable. In fact, all instances were
like this. It appeared that:
irqlat=$irqlat
Wasn't assigning the old $irqlat to the new irqlat variable, but
instead was assigning the $irqts to it.
The issue is that assigning the old $irqlat to the new irqlat variable
creates a variable reference alias, but the alias creation code
forgets to make sure the alias uses the same var_ref_idx to access the
reference.
Link: http://lkml.kernel.org/r/[email protected]
Cc: Linux Trace Devel <[email protected]>
Cc: linux-rt-users <[email protected]>
Cc: [email protected]
Fixes: 7e8b88a30b085 ("tracing: Add hist trigger support for variable reference aliases")
Reported-by: Steven Rostedt (VMware) <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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Add "gfp_t" support in synthetic_events, then the "gfp_t" type
parameter in some functions can be traced.
Prints the gfp flags as hex in addition to the human-readable flag
string. Example output:
whoopsie-630 [000] ...1 78.969452: testevent: bar=b20 (GFP_ATOMIC|__GFP_ZERO)
rcuc/0-11 [000] ...1 81.097555: testevent: bar=a20 (GFP_ATOMIC)
rcuc/0-11 [000] ...1 81.583123: testevent: bar=a20 (GFP_ATOMIC)
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Zhengjun Xing <[email protected]>
[ Added printing of flag names ]
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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Pass extra arguments to match operation for checking
exact match. If the event doesn't support exact match,
it will be ignored.
Link: http://lkml.kernel.org/r/156095685930.28024.10405547027475590975.stgit@devnote2
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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Without this check a snapshot is taken whenever a bucket's max is hit,
rather than only when the global max is hit, as it should be.
Before:
In this example, we do a first run of the workload (cyclictest),
examine the output, note the max ('triggering value') (347), then do
a second run and note the max again.
In this case, the max in the second run (39) is below the max in the
first run, but since we haven't cleared the histogram, the first max
is still in the histogram and is higher than any other max, so it
should still be the max for the snapshot. It isn't however - the
value should still be 347 after the second run.
# echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_waking/trigger
# echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0:onmax($wakeup_lat).save(next_prio,next_comm,prev_pid,prev_prio,prev_comm):onmax($wakeup_lat).snapshot() if next_comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
# cyclictest -p 80 -n -s -t 2 -D 2
# cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
{ next_pid: 2143 } hitcount: 199
max: 44 next_prio: 120 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/4
{ next_pid: 2145 } hitcount: 1325
max: 38 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/2
{ next_pid: 2144 } hitcount: 1982
max: 347 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/6
Snapshot taken (see tracing/snapshot). Details:
triggering value { onmax($wakeup_lat) }: 347
triggered by event with key: { next_pid: 2144 }
# cyclictest -p 80 -n -s -t 2 -D 2
# cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
{ next_pid: 2143 } hitcount: 199
max: 44 next_prio: 120 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/4
{ next_pid: 2148 } hitcount: 199
max: 16 next_prio: 120 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/1
{ next_pid: 2145 } hitcount: 1325
max: 38 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/2
{ next_pid: 2150 } hitcount: 1326
max: 39 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/4
{ next_pid: 2144 } hitcount: 1982
max: 347 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/6
{ next_pid: 2149 } hitcount: 1983
max: 130 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/0
Snapshot taken (see tracing/snapshot). Details:
triggering value { onmax($wakeup_lat) }: 39
triggered by event with key: { next_pid: 2150 }
After:
In this example, we do a first run of the workload (cyclictest),
examine the output, note the max ('triggering value') (375), then do
a second run and note the max again.
In this case, the max in the second run is still 375, the highest in
any bucket, as it should be.
# cyclictest -p 80 -n -s -t 2 -D 2
# cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
{ next_pid: 2072 } hitcount: 200
max: 28 next_prio: 120 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/5
{ next_pid: 2074 } hitcount: 1323
max: 375 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/2
{ next_pid: 2073 } hitcount: 1980
max: 153 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/6
Snapshot taken (see tracing/snapshot). Details:
triggering value { onmax($wakeup_lat) }: 375
triggered by event with key: { next_pid: 2074 }
# cyclictest -p 80 -n -s -t 2 -D 2
# cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
{ next_pid: 2101 } hitcount: 199
max: 49 next_prio: 120 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/6
{ next_pid: 2072 } hitcount: 200
max: 28 next_prio: 120 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/5
{ next_pid: 2074 } hitcount: 1323
max: 375 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/2
{ next_pid: 2103 } hitcount: 1325
max: 74 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/4
{ next_pid: 2073 } hitcount: 1980
max: 153 next_prio: 19 next_comm: cyclictest
prev_pid: 0 prev_prio: 120 prev_comm: swapper/6
{ next_pid: 2102 } hitcount: 1981
max: 84 next_prio: 19 next_comm: cyclictest
prev_pid: 12 prev_prio: 120 prev_comm: kworker/0:1
Snapshot taken (see tracing/snapshot). Details:
triggering value { onmax($wakeup_lat) }: 375
triggered by event with key: { next_pid: 2074 }
Link: http://lkml.kernel.org/r/95958351329f129c07504b4d1769c47a97b70d65.1555597045.git.tom.zanussi@linux.intel.com
Cc: [email protected]
Fixes: a3785b7eca8fd ("tracing: Add hist trigger snapshot() action")
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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There's an existing check for variable references in keys, but it
doesn't go far enough. It checks whether a key field is a variable
reference but doesn't check whether it's an expression containing
variable references, which can cause the same problems for callers.
Use the existing field_has_hist_vars() function rather than a direct
top-level flag check to catch all possible variable references.
Link: http://lkml.kernel.org/r/e8c3d3d53db5ca90ceea5a46e5413103a6902fc7.1555597045.git.tom.zanussi@linux.intel.com
Cc: [email protected]
Fixes: 067fe038e70f6 ("tracing: Add variable reference handling to hist triggers")
Reported-by: Vincent Bernat <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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hist_field_var_ref() is an implementation of hist_field_fn_t(), which
can be called with a null tracing_map_elt elt param when assembling a
key in event_hist_trigger().
In the case of hist_field_var_ref() this doesn't make sense, because a
variable can only be resolved by looking it up using an already
assembled key i.e. a variable can't be used to assemble a key since
the key is required in order to access the variable.
Upper layers should prevent the user from constructing a key using a
variable in the first place, but in case one slips through, it
shouldn't cause a NULL pointer dereference. Also if one does slip
through, we want to know about it, so emit a one-time warning in that
case.
Link: http://lkml.kernel.org/r/64ec8dc15c14d305295b64cdfcc6b2b9dd14753f.1555597045.git.tom.zanussi@linux.intel.com
Reported-by: Vincent Bernat <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing updates from Steven Rostedt:
"The major changes in this tracing update includes:
- Removal of non-DYNAMIC_FTRACE from 32bit x86
- Removal of mcount support from x86
- Emulating a call from int3 on x86_64, fixes live kernel patching
- Consolidated Tracing Error logs file
Minor updates:
- Removal of klp_check_compiler_support()
- kdb ftrace dumping output changes
- Accessing and creating ftrace instances from inside the kernel
- Clean up of #define if macro
- Introduction of TRACE_EVENT_NOP() to disable trace events based on
config options
And other minor fixes and clean ups"
* tag 'trace-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (44 commits)
x86: Hide the int3_emulate_call/jmp functions from UML
livepatch: Remove klp_check_compiler_support()
ftrace/x86: Remove mcount support
ftrace/x86_32: Remove support for non DYNAMIC_FTRACE
tracing: Simplify "if" macro code
tracing: Fix documentation about disabling options using trace_options
tracing: Replace kzalloc with kcalloc
tracing: Fix partial reading of trace event's id file
tracing: Allow RCU to run between postponed startup tests
tracing: Fix white space issues in parse_pred() function
tracing: Eliminate const char[] auto variables
ring-buffer: Fix mispelling of Calculate
tracing: probeevent: Fix to make the type of $comm string
tracing: probeevent: Do not accumulate on ret variable
tracing: uprobes: Re-enable $comm support for uprobe events
ftrace/x86_64: Emulate call function while updating in breakpoint handler
x86_64: Allow breakpoints to emulate call instructions
x86_64: Add gap to int3 to allow for call emulation
tracing: kdb: Allow ftdump to skip all but the last few entries
tracing: Add trace_total_entries() / trace_total_entries_cpu()
...
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The indirection through struct stack_trace is not necessary at all. Use the
storage array based interface.
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Tom Zanussi <[email protected]>
Reviewed-by: Tom Zanussi <[email protected]>
Reviewed-by: Josh Poimboeuf <[email protected]>
Acked-by: Steven Rostedt (VMware) <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Cc: Alexey Dobriyan <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: [email protected]
Cc: David Rientjes <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: [email protected]
Cc: Mike Rapoport <[email protected]>
Cc: Akinobu Mita <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: [email protected]
Cc: Robin Murphy <[email protected]>
Cc: Marek Szyprowski <[email protected]>
Cc: Johannes Thumshirn <[email protected]>
Cc: David Sterba <[email protected]>
Cc: Chris Mason <[email protected]>
Cc: Josef Bacik <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Mike Snitzer <[email protected]>
Cc: Alasdair Kergon <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Cc: Joonas Lahtinen <[email protected]>
Cc: Maarten Lankhorst <[email protected]>
Cc: [email protected]
Cc: David Airlie <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Miroslav Benes <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
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No architecture terminates the stack trace with ULONG_MAX anymore. As the
code checks the number of entries stored anyway there is no point in
keeping all that ULONG_MAX magic around.
The histogram code zeroes the storage before saving the stack, so if the
trace is shorter than the maximum number of entries it can terminate the
print loop if a zero entry is detected.
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Alexander Potapenko <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
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As each instance has their own error_log file, it makes more sense that the
instances show the errors of their own instead of all error_logs having the
same data. Make it that the errors show up in the instance error_log file
that the error happens in. If no instance trace_array is available, then
NULL can be passed in which will create the error in the top level instance
(the one at the top of the tracefs directory).
Reviewed-by: Masami Hiramatsu <[email protected]>
Reviewed-by: Tom Zanussi <[email protected]>
Tested-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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Have the trace_array that associates the trace instance of the histogram
passed around to functions so that error handling can display the error
message in the proper instance.
Reviewed-by: Masami Hiramatsu <[email protected]>
Reviewed-by: Tom Zanussi <[email protected]>
Tested-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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Replace hist_err() and hist_err_event() with tracing_log_err() from
the new tracing error_log mechanism.
Also add a couple related helper functions and remove most of the old
hist_err()-related code.
With this change, users no longer read the hist files for hist trigger
error information, but instead look at tracing/error_log for the same
information.
Link: http://lkml.kernel.org/r/c98f77a97c9715d18b623eeb5741057b330d5ac0.1554072478.git.tom.zanussi@linux.intel.com
Acked-by: Masami Hiramatsu <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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In preparation for making use of the new trace error log, save the
subsystem and event name associated with the last hist command - it
will be passed as the location param in the event_log_err() calls.
Link: http://lkml.kernel.org/r/eb0fd1362be8f39facb86c83eecf441b7a5876f8.1554072478.git.tom.zanussi@linux.intel.com
Acked-by: Masami Hiramatsu <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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Commit 656fe2ba85e8 (tracing: Use hist trigger's var_ref array to
destroy var_refs) centralized the destruction of all the var_refs
in one place so that other code didn't have to do it.
The track_data_destroy() added later ignored that and also destroyed
the track_data var_ref, causing a double-free error flagged by KASAN.
==================================================================
BUG: KASAN: use-after-free in destroy_hist_field+0x30/0x70
Read of size 8 at addr ffff888086df2210 by task bash/1694
CPU: 6 PID: 1694 Comm: bash Not tainted 5.1.0-rc1-test+ #15
Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03
07/14/2016
Call Trace:
dump_stack+0x71/0xa0
? destroy_hist_field+0x30/0x70
print_address_description.cold.3+0x9/0x1fb
? destroy_hist_field+0x30/0x70
? destroy_hist_field+0x30/0x70
kasan_report.cold.4+0x1a/0x33
? __kasan_slab_free+0x100/0x150
? destroy_hist_field+0x30/0x70
destroy_hist_field+0x30/0x70
track_data_destroy+0x55/0xe0
destroy_hist_data+0x1f0/0x350
hist_unreg_all+0x203/0x220
event_trigger_open+0xbb/0x130
do_dentry_open+0x296/0x700
? stacktrace_count_trigger+0x30/0x30
? generic_permission+0x56/0x200
? __x64_sys_fchdir+0xd0/0xd0
? inode_permission+0x55/0x200
? security_inode_permission+0x18/0x60
path_openat+0x633/0x22b0
? path_lookupat.isra.50+0x420/0x420
? __kasan_kmalloc.constprop.12+0xc1/0xd0
? kmem_cache_alloc+0xe5/0x260
? getname_flags+0x6c/0x2a0
? do_sys_open+0x149/0x2b0
? do_syscall_64+0x73/0x1b0
? entry_SYSCALL_64_after_hwframe+0x44/0xa9
? _raw_write_lock_bh+0xe0/0xe0
? __kernel_text_address+0xe/0x30
? unwind_get_return_address+0x2f/0x50
? __list_add_valid+0x2d/0x70
? deactivate_slab.isra.62+0x1f4/0x5a0
? getname_flags+0x6c/0x2a0
? set_track+0x76/0x120
do_filp_open+0x11a/0x1a0
? may_open_dev+0x50/0x50
? _raw_spin_lock+0x7a/0xd0
? _raw_write_lock_bh+0xe0/0xe0
? __alloc_fd+0x10f/0x200
do_sys_open+0x1db/0x2b0
? filp_open+0x50/0x50
do_syscall_64+0x73/0x1b0
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fa7b24a4ca2
Code: 25 00 00 41 00 3d 00 00 41 00 74 4c 48 8d 05 85 7a 0d 00 8b 00 85 c0
75 6d 89 f2 b8 01 01 00 00 48 89 fe bf 9c ff ff ff 0f 05 <48> 3d 00 f0 ff ff
0f 87 a2 00 00 00 48 8b 4c 24 28 64 48 33 0c 25
RSP: 002b:00007fffbafb3af0 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 000055d3648ade30 RCX: 00007fa7b24a4ca2
RDX: 0000000000000241 RSI: 000055d364a55240 RDI: 00000000ffffff9c
RBP: 00007fffbafb3bf0 R08: 0000000000000020 R09: 0000000000000002
R10: 00000000000001b6 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000003 R14: 0000000000000001 R15: 000055d364a55240
==================================================================
So remove the track_data_destroy() destroy_hist_field() call for that
var_ref.
Link: http://lkml.kernel.org/r/[email protected]
Fixes: 466f4528fbc69 ("tracing: Generalize hist trigger onmax and save action")
Reported-by: Steven Rostedt (VMware) <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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Because there may be random garbage beyond a string's null terminator,
code that might use the entire comm array e.g. histogram keys, can
give unexpected results if that garbage is copied in too, so avoid
that possibility by using strncpy instead of memcpy.
Link: http://lkml.kernel.org/r/1eb9f096a8086c3c82c7fc087c900005143cec54.1551802084.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Because there may be random garbage beyond a string's null terminator,
it's not correct to copy the the complete character array for use as a
hist trigger key. This results in multiple histogram entries for the
'same' string key.
So, in the case of a string key, use strncpy instead of memcpy to
avoid copying in the extra bytes.
Before, using the gdbus entries in the following hist trigger as an
example:
# echo 'hist:key=comm' > /sys/kernel/debug/tracing/events/sched/sched_waking/trigger
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist
...
{ comm: ImgDecoder #4 } hitcount: 203
{ comm: gmain } hitcount: 213
{ comm: gmain } hitcount: 216
{ comm: StreamTrans #73 } hitcount: 221
{ comm: mozStorage #3 } hitcount: 230
{ comm: gdbus } hitcount: 233
{ comm: StyleThread#5 } hitcount: 253
{ comm: gdbus } hitcount: 256
{ comm: gdbus } hitcount: 260
{ comm: StyleThread#4 } hitcount: 271
...
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l
51
After:
# cat /sys/kernel/debug/tracing/events/sched/sched_waking/hist | egrep gdbus | wc -l
1
Link: http://lkml.kernel.org/r/50c35ae1267d64eee975b8125e151e600071d4dc.1549309756.git.tom.zanussi@linux.intel.com
Cc: Namhyung Kim <[email protected]>
Cc: [email protected]
Fixes: 79e577cbce4c4 ("tracing: Support string type key properly")
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Since we now have a str_has_prefix() that returns the length, we can
use that instead of explicitly calculating it.
Link: http://lkml.kernel.org/r/03418373fd1e80030e7394b8e3e081c5de28a710.1549309756.git.tom.zanussi@linux.intel.com
Cc: Joe Perches <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Add a 'trace(synthetic_event_name, params)' alternative to
synthetic_event_name(params).
Currently, the syntax used for generating synthetic events is to
invoke synthetic_event_name(params) i.e. use the synthetic event name
as a function call.
Users requested a new form that more explicitly shows that the
synthetic event is in effect being traced. In this version, a new
'trace()' keyword is used, and the synthetic event name is passed in
as the first argument.
In addition, for the sake of consistency with other actions, change
the documention to emphasize the trace() form over the function-call
form, which remains documented as equivalent.
Link: http://lkml.kernel.org/r/d082773e50232a001480cf837679a1e01c1a2eb7.1550100284.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Add support for a hist:onchange($var) handler, similar to the onmax()
handler but triggering whenever there's any change in $var, not just a
max.
Link: http://lkml.kernel.org/r/dfbc7e4ada242603e9ec3f049b5ad076a07dfd03.1550100284.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Add support for hist:handlerXXX($var).snapshot(), which will take a
snapshot of the current trace buffer whenever handlerXXX is hit.
As a first user, this also adds snapshot() action support for the
onmax() handler i.e. hist:onmax($var).snapshot().
Also, the hist trigger key printing is moved into a separate function
so the snapshot() action can print a histogram key outside the
histogram display - add and use hist_trigger_print_key() for that
purpose.
Link: http://lkml.kernel.org/r/2f1a952c0dcd8aca8702ce81269581a692396d45.1550100284.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
The action refactor code allowed actions and handlers to be separated,
but the existing onmax handler and save action code is still not
flexible enough to handle arbitrary coupling. This change generalizes
them and in the process makes additional handlers and actions easier
to implement.
The onmax action can be broken up and thought of as two separate
components - a variable to be tracked (the parameter given to the
onmax($var_to_track) function) and an invisible variable created to
save the ongoing result of doing something with that variable, such as
saving the max value of that variable so far seen.
Separating it out like this and renaming it appropriately allows us to
use the same code for similar tracking functions such as
onchange($var_to_track), which would just track the last value seen
rather than the max seen so far, which is useful in some situations.
Additionally, because different handlers and actions may want to save
and access data differently e.g. save and retrieve tracking values as
local variables vs something more global, save_val() and get_val()
interface functions are introduced and max-specific implementations
are used instead.
The same goes for the code that checks whether a maximum has been hit
- a generic check_val() interface and max-checking implementation is
used instead, which allows future patches to make use of he same code
using their own implemetations of similar functionality.
Link: http://lkml.kernel.org/r/980ea73dd8e3f36db3d646f99652f8fed42b77d4.1550100284.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Currently, the onmatch action data binds the onmatch action to data
related to synthetic event generation. Since we want to allow the
onmatch handler to potentially invoke a different action, and because
we expect other handlers to generate synthetic events, we need to
separate the data related to these two functions.
Also rename the onmatch data to something more descriptive, and create
and use common action data destroy function.
Link: http://lkml.kernel.org/r/b9abbf9aae69fe3920cdc8ddbcaad544dd258d78.1550100284.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
The hist trigger action code currently implements two essentially
hard-coded pairs of 'actions' - onmax(), which tracks a variable and
saves some event fields when a max is hit, and onmatch(), which is
hard-coded to generate a synthetic event.
These hardcoded pairs (track max/save fields and detect match/generate
synthetic event) should really be decoupled into separate components
that can then be arbitrarily combined. The first component of each
pair (track max/detect match) is called a 'handler' in the new code,
while the second component (save fields/generate synthetic event) is
called an 'action' in this scheme.
This change refactors the action code to reflect this split by adding
two handlers, HANDLER_ONMATCH and HANDLER_ONMAX, along with two
actions, ACTION_SAVE and ACTION_TRACE.
The new code combines them to produce the existing ONMATCH/TRACE and
ONMAX/SAVE functionality, but doesn't implement the other combinations
now possible. Future patches will expand these to further useful
cases, such as ONMAX/TRACE, as well as add additional handlers and
actions such as ONCHANGE and SNAPSHOT.
Also, add abbreviated documentation for handlers and actions to
README.
Link: http://lkml.kernel.org/r/98bfdd48c1b4ff29fc5766442f99f5bc3c34b76b.1550100284.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
prefix
As str_has_prefix() returns the length on match, we can use that for the
updating of the string pointer instead of recalculating the prefix size.
Cc: Tom Zanussi <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
There are several instances of strncmp(str, "const", 123), where 123 is the
strlen of the const string to check if "const" is the prefix of str. But
this can be error prone. Use str_has_prefix() instead.
Acked-by: Namhyung Kim <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
The tracing histogram code contains a lot of instances of the construct:
strncmp(str, "const", sizeof("const") - 1)
This can be prone to bugs due to typos or bad cut and paste. Use the
str_has_prefix() helper macro instead that removes the need for having two
copies of the constant string.
Cc: Tom Zanussi <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Add a few comments to help clarify how variable and variable reference
fields are used in the code.
Link: http://lkml.kernel.org/r/ea857ce948531d7bec712bbb0f38360aa1d378ec.1545161087.git.tom.zanussi@linux.intel.com
Acked-by: Namhyung Kim <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
All var_refs are now handled uniformly and there's no reason to treat
the synth_refs in a special way now, so remove them and associated
functions.
Link: http://lkml.kernel.org/r/b4d3470526b8f0426dcec125399dad9ad9b8589d.1545161087.git.tom.zanussi@linux.intel.com
Acked-by: Namhyung Kim <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Since every var ref for a trigger has an entry in the var_ref[] array,
use that to destroy the var_refs, instead of piecemeal via the field
expressions.
This allows us to avoid having to keep and treat differently separate
lists for the action-related references, which future patches will
remove.
Link: http://lkml.kernel.org/r/fad1a164f0e257c158e70d6eadbf6c586e04b2a2.1545161087.git.tom.zanussi@linux.intel.com
Acked-by: Namhyung Kim <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Have create_var_ref() manage the hist trigger's var_ref list, rather
than having similar code doing it in multiple places. This cleans up
the code and makes sure var_refs are always accounted properly.
Also, document the var_ref-related functions to make what their
purpose clearer.
Link: http://lkml.kernel.org/r/05ddae93ff514e66fc03897d6665231892939913.1545161087.git.tom.zanussi@linux.intel.com
Acked-by: Namhyung Kim <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Since all the variable reference hist_fields are collected into
hist_data->var_refs[] array, there's no need to go through all the
fields looking for them, or in separate arrays like synth_var_refs[],
which will be going away soon anyway.
This also allows us to get rid of some unnecessary code and functions
currently used for the same purpose.
Link: http://lkml.kernel.org/r/[email protected]
Acked-by: Namhyung Kim <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
There's no need to use strlen() for static strings when the length is
already known, so update trace_events_hist.c with sizeof() for those
cases.
Link: http://lkml.kernel.org/r/e3e754f2bd18e56eaa8baf79bee619316ebf4cfc.1545161087.git.tom.zanussi@linux.intel.com
Acked-by: Namhyung Kim <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
hist_field.var_idx is completely unused, so remove it.
Link: http://lkml.kernel.org/r/d4e066c0f509f5f13ad3babc8c33ca6e7ddc439a.1545161087.git.tom.zanussi@linux.intel.com
Acked-by: Namhyung Kim <[email protected]>
Reviewed-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
The trace_add/remove_event_call_nolock() functions were added to allow
the tace_add/remove_event_call() code be called when the event_mutex
lock was already taken. Now that all callers are done within the
event_mutex, there's no reason to have two different interfaces.
Remove the current wrapper trace_add/remove_event_call()s and rename the
_nolock versions back to the original names.
Link: http://lkml.kernel.org/r/154140866955.17322.2081425494660638846.stgit@devbox
Acked-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Rmove unneeded synth_event_mutex. This mutex protects the reference
count in synth_event, however, those operational points are already
protected by event_mutex.
1. In __create_synth_event() and create_or_delete_synth_event(),
those synth_event_mutex clearly obtained right after event_mutex.
2. event_hist_trigger_func() is trigger_hist_cmd.func() which is
called by trigger_process_regex(), which is a part of
event_trigger_regex_write() and this function takes event_mutex.
3. hist_unreg_all() is trigger_hist_cmd.unreg_all() which is called
by event_trigger_regex_open() and it takes event_mutex.
4. onmatch_destroy() and onmatch_create() have long call tree,
but both are finally invoked from event_trigger_regex_write()
and event_trace_del_tracer(), former takes event_mutex, and latter
ensures called under event_mutex locked.
Finally, I ensured there is no resource conflict. For safety,
I added lockdep_assert_held(&event_mutex) for each function.
Link: http://lkml.kernel.org/r/154140864134.17322.4796059721306031894.stgit@devbox
Reviewed-by: Tom Zanussi <[email protected]>
Tested-by: Tom Zanussi <[email protected]>
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Use dyn_event framework for synthetic events. This shows
synthetic events on "tracing/dynamic_events" file in addition
to tracing/synthetic_events interface.
User can also define new events via tracing/dynamic_events
with "s:" prefix. So, the new syntax is below;
s:[synthetic/]EVENT_NAME TYPE ARG; [TYPE ARG;]...
To remove events via tracing/dynamic_events, you can use
"-:" prefix as same as other events.
Link: http://lkml.kernel.org/r/154140861301.17322.15454611233735614508.stgit@devbox
Reviewed-by: Tom Zanussi <[email protected]>
Tested-by: Tom Zanussi <[email protected]>
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Since the event_mutex and synth_event_mutex ordering issue
is gone, we can skip existing event check when adding or
deleting events, and some redundant code in error path.
This changes release_all_synth_events() to abort the process
when it hits any error and returns the error code. It succeeds
only if it has no error.
Link: http://lkml.kernel.org/r/154140847194.17322.17960275728005067803.stgit@devbox
Reviewed-by: Tom Zanussi <[email protected]>
Tested-by: Tom Zanussi <[email protected]>
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
synthetic event is using synth_event_mutex for protecting
synth_event_list, and event_trigger_write() path acquires
locks as below order.
event_trigger_write(event_mutex)
->trigger_process_regex(trigger_cmd_mutex)
->event_hist_trigger_func(synth_event_mutex)
On the other hand, synthetic event creation and deletion paths
call trace_add_event_call() and trace_remove_event_call()
which acquires event_mutex. In that case, if we keep the
synth_event_mutex locked while registering/unregistering synthetic
events, its dependency will be inversed.
To avoid this issue, current synthetic event is using a 2 phase
process to create/delete events. For example, it searches existing
events under synth_event_mutex to check for event-name conflicts, and
unlocks synth_event_mutex, then registers a new event under event_mutex
locked. Finally, it locks synth_event_mutex and tries to add the
new event to the list. But it can introduce complexity and a chance
for name conflicts.
To solve this simpler, this introduces trace_add_event_call_nolock()
and trace_remove_event_call_nolock() which don't acquire
event_mutex inside. synthetic event can lock event_mutex before
synth_event_mutex to solve the lock dependency issue simpler.
Link: http://lkml.kernel.org/r/154140844377.17322.13781091165954002713.stgit@devbox
Reviewed-by: Tom Zanussi <[email protected]>
Tested-by: Tom Zanussi <[email protected]>
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Return -ENOENT error if there is no target synthetic event.
This notices an operation failure to user as below;
# echo 'wakeup_latency u64 lat; pid_t pid;' > synthetic_events
# echo '!wakeup' >> synthetic_events
sh: write error: No such file or directory
Link: http://lkml.kernel.org/r/154013449986.25576.9487131386597290172.stgit@devbox
Acked-by: Tom Zanussi <[email protected]>
Tested-by: Tom Zanussi <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Rajvi Jingar <[email protected]>
Cc: [email protected]
Fixes: 4b147936fa50 ('tracing: Add support for 'synthetic' events')
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Fix synthetic event to allow independent semicolon at end.
The synthetic_events interface accepts a semicolon after the
last word if there is no space.
# echo "myevent u64 var;" >> synthetic_events
But if there is a space, it returns an error.
# echo "myevent u64 var ;" > synthetic_events
sh: write error: Invalid argument
This behavior is difficult for users to understand. Let's
allow the last independent semicolon too.
Link: http://lkml.kernel.org/r/153986835420.18251.2191216690677025744.stgit@devbox
Cc: Shuah Khan <[email protected]>
Cc: Tom Zanussi <[email protected]>
Cc: [email protected]
Fixes: commit 4b147936fa50 ("tracing: Add support for 'synthetic' events")
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Fix synthetic event to accept unsigned modifier for its field type
correctly.
Currently, synthetic_events interface returns error for "unsigned"
modifiers as below;
# echo "myevent unsigned long var" >> synthetic_events
sh: write error: Invalid argument
This is because argv_split() breaks "unsigned long" into "unsigned"
and "long", but parse_synth_field() doesn't expected it.
With this fix, synthetic_events can handle the "unsigned long"
correctly like as below;
# echo "myevent unsigned long var" >> synthetic_events
# cat synthetic_events
myevent unsigned long var
Link: http://lkml.kernel.org/r/153986832571.18251.8448135724590496531.stgit@devbox
Cc: Shuah Khan <[email protected]>
Cc: Tom Zanussi <[email protected]>
Cc: [email protected]
Fixes: commit 4b147936fa50 ("tracing: Add support for 'synthetic' events")
Signed-off-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Add the SPDX License header to ease license compliance management.
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
tracepoint_synchronize_unregister()
Now that some trace events can be protected by srcu_read_lock(tracepoint_srcu),
we need to make sure all locations that depend on this are also protected.
There were many places that did a synchronize_sched() thinking that it was
enough to protect againts access to trace events. This use to be the case,
but now that we use SRCU for _rcuidle() trace events, they may not be
protected by synchronize_sched(), as they may be called in paths that RCU is
not watching for preempt disable.
Fixes: e6753f23d961d ("tracepoint: Make rcuidle tracepoint callers use SRCU")
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
'err' is used as a NUL-terminated string, but using strncpy() with the length
equal to the buffer size may result in lack of the termination:
kernel/trace/trace_events_hist.c: In function 'hist_err_event':
kernel/trace/trace_events_hist.c:396:3: error: 'strncpy' specified bound 256 equals destination size [-Werror=stringop-truncation]
strncpy(err, var, MAX_FILTER_STR_VAL);
This changes it to use the safer strscpy() instead.
Link: http://lkml.kernel.org/r/[email protected]
Cc: [email protected]
Fixes: f404da6e1d46 ("tracing: Add 'last error' error facility for hist triggers")
Acked-by: Tom Zanussi <[email protected]>
Signed-off-by: Arnd Bergmann <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
Now that trace_marker can have triggers, including a histogram triggers, the
onmatch() and onmax() access the trace event. To do so, the search routine
to find the event file needs to use the raw __find_event_file() that does
not filter out ftrace events.
Reviewed-by: Namhyung Kim <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
If the user specifies an invalid field modifier for a hist trigger,
the current code correctly flags that as an error, but doesn't tell
the user what happened.
Fix this by invoking hist_err() with an appropriate message when
invalid modifiers are specified.
Before:
# echo 'hist:keys=pid:ts0=common_timestamp.junkusecs' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
-su: echo: write error: Invalid argument
# cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
After:
# echo 'hist:keys=pid:ts0=common_timestamp.junkusecs' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
-su: echo: write error: Invalid argument
# cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/hist
ERROR: Invalid field modifier: junkusecs
Last command: keys=pid:ts0=common_timestamp.junkusecs
Link: http://lkml.kernel.org/r/b043c59fa79acd06a5f14a1d44dee9e5a3cd1248.1524790601.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
If the user specifies a nonexistent field for a hist trigger, the
current code correctly flags that as an error, but doesn't tell the
user what happened.
Fix this by invoking hist_err() with an appropriate message when
nonexistent fields are specified.
Before:
# echo 'hist:keys=pid:ts0=common_timestamp.usecs' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
-su: echo: write error: Invalid argument
# cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
After:
# echo 'hist:keys=pid:ts0=common_timestamp.usecs' >> /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
-su: echo: write error: Invalid argument
# cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
ERROR: Couldn't find field: pid
Last command: keys=pid:ts0=common_timestamp.usecs
Link: http://lkml.kernel.org/r/fdc8746969d16906120f162b99dd71c741e0b62c.1524790601.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Reported-by: Masami Hiramatsu <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
|
|
The flag-printing code used when displaying hist triggers somehow got
dropped during refactoring of the inter-event patchset. This restores
it.
Below are a couple examples - in the first case, .usecs wasn't being
displayed properly for common_timestamps and the second illustrates
the same for other flags such as .execname.
Before:
# echo 'hist:key=common_pid.execname:val=count:sort=count' > /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/trigger
# cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/trigger
hist:keys=common_pid:vals=hitcount,count:sort=count:size=2048 [active]
# echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
# cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
hist:keys=pid:vals=hitcount:ts0=common_timestamp:sort=hitcount:size=2048:clock=global if comm=="cyclictest" [active]
After:
# echo 'hist:key=common_pid.execname:val=count:sort=count' > /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/trigger
# cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/trigger
hist:keys=common_pid.execname:vals=hitcount,count:sort=count:size=2048 [active]
# echo 'hist:keys=pid:ts0=common_timestamp.usecs if comm=="cyclictest"' >> /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
# cat /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger
hist:keys=pid:vals=hitcount:ts0=common_timestamp.usecs:sort=hitcount:size=2048:clock=global if comm=="cyclictest" [active]
Link: http://lkml.kernel.org/r/492bab42ff21806600af98a8ea901af10efbee0c.1524790601.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <[email protected]>
Signed-off-by: Steven Rostedt (VMware) <[email protected]>
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