[ Upstream commit 8ce939a0fa194939cc1f92dbd8bc1a7806e7d40a ] The event may have been updated in the PMU-specific implementation, e.g., Intel PEBS counters snapshotting. The common code should not read and overwrite the value. The PERF_SAMPLE_READ in the data->sample_type can be used to detect whether the PMU-specific value is available. If yes, avoid the pmu->read() in the common code. Add a new flag, skip_read, to track the case. Factor out a perf_pmu_read() to clean up the code. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Kan Liang <kan.liang@linux.intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20250121152303.3128733-3-kan.liang@linux.intel.com Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 66477c7230eb1f9b90deb8c0f4da2bac2053c329 ] When f_ops->mmap() returns failure, m_ops->close() is *not* called. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com> Link: https://lore.kernel.org/r/20241104135519.248358497@infradead.org Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit da02f54e81db2f7bf6af9d1d0cfc5b41ec6d0dcb ] Make sure that perf_try_init_event() doesn't leave event->pmu nor event->destroy set on failure. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Acked-by: Ravi Bangoria <ravi.bangoria@amd.com> Link: https://lore.kernel.org/r/20250205102449.110145835@infradead.org Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 0ba3a4ab76fd3367b9cb680cad70182c896c795c ] Move the get_ctx(child_ctx) call and the child_event->ctx assignment to occur immediately after the child event is allocated. Ensure that child_event->ctx is non-NULL before any subsequent error path within inherit_event calls free_event(), satisfying the assumptions of the cleanup code. Details: There's no clear Fixes tag, because this bug is a side-effect of multiple interacting commits over time (up to 15 years old), not a single regression. The code initially incremented refcount then assigned context immediately after the child_event was created. Later, an early validity check for child_event was added before the refcount/assignment. Even later, a WARN_ON_ONCE() cleanup check was added, assuming event->ctx is valid if the pmu_ctx is valid. The problem is that the WARN_ON_ONCE() could trigger after the initial check passed but before child_event->ctx was assigned, violating its precondition. The solution is to assign child_event->ctx right after its initial validation. This ensures the context exists for any subsequent checks or cleanup routines, resolving the WARN_ON_ONCE(). To resolve it, defer the refcount update and child_event->ctx assignment directly after child_event->pmu_ctx is set but before checking if the parent event is orphaned. The cleanup routine depends on event->pmu_ctx being non-NULL before it verifies event->ctx is non-NULL. This also maintains the author's original intent of passing in child_ctx to find_get_pmu_context before its refcount/assignment. [ mingo: Expanded the changelog from another email by Gabriel Shahrouzi. ] Reported-by: syzbot+ff3aa851d46ab82953a3@syzkaller.appspotmail.com Signed-off-by: Gabriel Shahrouzi <gshahrouzi@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi Bangoria <ravi.bangoria@amd.com> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Link: https://lore.kernel.org/r/20250405203036.582721-1-gshahrouzi@gmail.com Closes: https://syzkaller.appspot.com/bug?extid=ff3aa851d46ab82953a3 Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit 56799bc035658738f362acec3e7647bb84e68933 ]
Perf can hang while freeing a sigtrap event if a related deferred
signal hadn't managed to be sent before the file got closed:
perf_event_overflow()
task_work_add(perf_pending_task)
fput()
task_work_add(____fput())
task_work_run()
____fput()
perf_release()
perf_event_release_kernel()
_free_event()
perf_pending_task_sync()
task_work_cancel() -> FAILED
rcuwait_wait_event()
Once task_work_run() is running, the list of pending callbacks is
removed from the task_struct and from this point on task_work_cancel()
can't remove any pending and not yet started work items, hence the
task_work_cancel() failure and the hang on rcuwait_wait_event().
Task work could be changed to remove one work at a time, so a work
running on the current task can always cancel a pending one, however
the wait / wake design is still subject to inverted dependencies when
remote targets are involved, as pictured by Oleg:
T1 T2
fd = perf_event_open(pid => T2->pid); fd = perf_event_open(pid => T1->pid);
close(fd) close(fd)
<IRQ> <IRQ>
perf_event_overflow() perf_event_overflow()
task_work_add(perf_pending_task) task_work_add(perf_pending_task)
</IRQ> </IRQ>
fput() fput()
task_work_add(____fput()) task_work_add(____fput())
task_work_run() task_work_run()
____fput() ____fput()
perf_release() perf_release()
perf_event_release_kernel() perf_event_release_kernel()
_free_event() _free_event()
perf_pending_task_sync() perf_pending_task_sync()
rcuwait_wait_event() rcuwait_wait_event()
Therefore the only option left is to acquire the event reference count
upon queueing the perf task work and release it from the task work, just
like it was done before 3a5465418f5f ("perf: Fix event leak upon exec and file release")
but without the leaks it fixed.
Some adjustments are necessary to make it work:
* A child event might dereference its parent upon freeing. Care must be
taken to release the parent last.
* Some places assuming the event doesn't have any reference held and
therefore can be freed right away must instead put the reference and
let the reference counting to its job.
Reported-by: "Yi Lai" <yi1.lai@linux.intel.com>
Closes: https://lore.kernel.org/all/Zx9Losv4YcJowaP%2F@ly-workstation/
Reported-by: syzbot+3c4321e10eea460eb606@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/673adf75.050a0220.87769.0024.GAE@google.com/
Fixes: 3a5465418f5f ("perf: Fix event leak upon exec and file release")
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250304135446.18905-1-frederic@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit c70ca298036c58a88686ff388d3d367e9d21acf0 ]
The error cleanup sequence in perf_event_alloc() is a subset of the
existing _free_event() function (it must of course be).
Split this out into __free_event() and simplify the error path.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Ravi Bangoria <ravi.bangoria@amd.com>
Link: https://lore.kernel.org/r/20241104135517.967889521@infradead.org
Stable-dep-of: 56799bc03565 ("perf: Fix hang while freeing sigtrap event")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit a3c3c66670cee11eb13aa43905904bf29cb92d32 ]
The perf events code fails to account for total_time_enabled of
inactive events.
Here is a failure case for accounting total_time_enabled for
CPU PMU events:
sudo ./perf stat -vvv -e armv8_pmuv3_0/event=0x08/ -e armv8_pmuv3_1/event=0x08/ -- stress-ng --pthread=2 -t 2s
...
armv8_pmuv3_0/event=0x08/: 1138698008 2289429840 2174835740
armv8_pmuv3_1/event=0x08/: 1826791390 1950025700 847648440
` ` `
` ` > total_time_running with child
` > total_time_enabled with child
> count with child
Performance counter stats for 'stress-ng --pthread=2 -t 2s':
1,138,698,008 armv8_pmuv3_0/event=0x08/ (94.99%)
1,826,791,390 armv8_pmuv3_1/event=0x08/ (43.47%)
The two events above are opened on two different CPU PMUs, for example,
each event is opened for a cluster in an Arm big.LITTLE system, they
will never run on the same CPU. In theory, the total enabled time should
be same for both events, as two events are opened and closed together.
As the result show, the two events' total enabled time including
child event is different (2289429840 vs 1950025700).
This is because child events are not accounted properly
if a event is INACTIVE state when the task exits:
perf_event_exit_event()
`> perf_remove_from_context()
`> __perf_remove_from_context()
`> perf_child_detach() -> Accumulate child_total_time_enabled
`> list_del_event() -> Update child event's time
The problem is the time accumulation happens prior to child event's
time updating. Thus, it misses to account the last period's time when
the event exits.
The perf core layer follows the rule that timekeeping is tied to state
change. To address the issue, make __perf_remove_from_context()
handle the task exit case by passing 'DETACH_EXIT' to it and
invoke perf_event_state() for state alongside with accounting the time.
Then, perf_child_detach() populates the time into the parent's time metrics.
After this patch, the bug is fixed:
sudo ./perf stat -vvv -e armv8_pmuv3_0/event=0x08/ -e armv8_pmuv3_1/event=0x08/ -- stress-ng --pthread=2 -t 10s
...
armv8_pmuv3_0/event=0x08/: 15396770398 32157963940 21898169000
armv8_pmuv3_1/event=0x08/: 22428964974 32157963940 10259794940
Performance counter stats for 'stress-ng --pthread=2 -t 10s':
15,396,770,398 armv8_pmuv3_0/event=0x08/ (68.10%)
22,428,964,974 armv8_pmuv3_1/event=0x08/ (31.90%)
[ mingo: Clarified the changelog. ]
Fixes: ef54c1a476aef ("perf: Rework perf_event_exit_event()")
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Leo Yan <leo.yan@arm.com>
Link: https://lore.kernel.org/r/20250326082003.1630986-1-yeoreum.yun@arm.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit d57e94f5b891925e4f2796266eba31edd5a01903 ]
To save/restore LBR call stack data in system-wide mode, the task_struct
information is required.
Extend the parameters of sched_task() to supply task_struct information.
When schedule in, the LBR call stack data for new task will be restored.
When schedule out, the LBR call stack data for old task will be saved.
Only need to pass the required task_struct information.
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250314172700.438923-4-kan.liang@linux.intel.com
Stable-dep-of: 3cec9fd03543 ("perf/x86/lbr: Fix shorter LBRs call stacks for the system-wide mode")
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ Upstream commit cb4369129339060218baca718a578bb0b826e734 ]
Some PMU specific data has to be saved/restored during context switch,
e.g. LBR call stack data. Currently, the data is saved in event context
structure, but only for per-process event. For system-wide event,
because of missing the LBR call stack data after context switch, LBR
callstacks are always shorter in comparison to per-process mode.
For example,
Per-process mode:
$perf record --call-graph lbr -- taskset -c 0 ./tchain_edit
- 99.90% 99.86% tchain_edit tchain_edit [.] f3
99.86% _start
__libc_start_main
generic_start_main
main
f1
- f2
f3
System-wide mode:
$perf record --call-graph lbr -a -- taskset -c 0 ./tchain_edit
- 99.88% 99.82% tchain_edit tchain_edit [.] f3
- 62.02% main
f1
f2
f3
- 28.83% f1
- f2
f3
- 28.83% f1
- f2
f3
- 8.88% generic_start_main
main
f1
f2
f3
It isn't practical to simply allocate the data for system-wide event in
CPU context structure for all tasks. We have no idea which CPU a task
will be scheduled to. The duplicated LBR data has to be maintained on
every CPU context structure. That's a huge waste. Otherwise, the LBR
data still lost if the task is scheduled to another CPU.
Save the pmu specific data in task_struct. The size of pmu specific data
is 788 bytes for LBR call stack. Usually, the overall amount of threads
doesn't exceed a few thousands. For 10K threads, keeping LBR data would
consume additional ~8MB. The additional space will only be allocated
during LBR call stack monitoring. It will be released when the
monitoring is finished.
Furthermore, moving task_ctx_data from perf_event_context to task_struct
can reduce complexity and make things clearer. E.g. perf doesn't need to
swap task_ctx_data on optimized context switch path.
This patch set is just the first step. There could be other
optimization/extension on top of this patch set. E.g. for cgroup
profiling, perf just needs to save/store the LBR call stack information
for tasks in specific cgroup. That could reduce the additional space.
Also, the LBR call stack can be available for software events, or allow
even debugging use cases, like LBRs on crash later.
Because of the alignment requirement of Intel Arch LBR, the Kmem cache
is used to allocate the PMU specific data. It's required when child task
allocates the space. Save it in struct perf_ctx_data.
The refcount in struct perf_ctx_data is used to track the users of pmu
specific data.
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Alexey Budankov <alexey.budankov@linux.intel.com>
Link: https://lore.kernel.org/r/20250314172700.438923-1-kan.liang@linux.intel.com
Stable-dep-of: 3cec9fd03543 ("perf/x86/lbr: Fix shorter LBRs call stacks for the system-wide mode")
Signed-off-by: Sasha Levin <sashal@kernel.org>
There is a fairly obvious race between perf_init_event() doing idr_find() and perf_pmu_register() doing idr_alloc() with an incompletely initialized PMU pointer. Avoid by doing idr_alloc() on a NULL pointer to register the id, and swizzling the real struct pmu pointer at the end using idr_replace(). Also making sure to not set struct pmu members after publishing the struct pmu, duh. [ introduce idr_cmpxchg() in order to better handle the idr_replace() error case -- if it were to return an unexpected pointer, it will already have replaced the value and there is no going back. ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20241104135517.858805880@infradead.org