github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-09-13 15:40:03 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

s390/pai: Handle multiple PMU stop callback invocations

Browse Source 
Handle the following scenario:
The kernel protects itself against a very high sampling load and
throttles the sampling using:

  perf_event_throttle() --> PMU->stop()

Shortly later the scheduler may terminate the task and removes it from the
CPU. It again calls

  PMU->stop()

which results in two invocations of PMU->stop() called back to back.
Protect against this and check the PERF_HES_STOPPED bit on function
entry.  If it is already set return.
Clear bit PERF_HES_STOPPED in PMU->start().

Prohibit ioctl(fd, PERF_EVENT_IOC_PERIOD, ...) call for this event.
It sets perf_event::event_limit to a positive value and causes
perf_event_overflow() to invoke pai_stop() call back function when
perf_event::event_limit hits zero. This is not supported because the
sample events CRYPTO_ALL and NNPA_ALL are only taken at schedule out
of a task.

Use list_for_each_entry_safe() for safe iteration over syswide_list
in pai_have_samples().

Fixes: 9f66572f28 ("s390/pai_crypto: Enable per-task and system-wide sampling event")
Fixes: 582cc1b28e ("s390/pai_ext: Enable per-task and system-wide sampling event")
Cc: stable@vger.kernel.org # v6.19+
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Thomas Richter 2026-08-19 07:58:55 +02:00 committed by Heiko Carstens
parent 439077c39d
commit f3110e969a
1 changed files with 23 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

25
arch/s390/kernel/perf_pai.c
View File

@ -464,6 +464,7 @@ static void pai_start(struct perf_event *event, int flags,
cpump->event = event;
}
}
event->hw.state &= ~PERF_HES_STOPPED;
}
static void paicrypt_start(struct perf_event *event, int flags)
@ -510,6 +511,13 @@ static void pai_stop(struct perf_event *event, int flags)
struct pai_mapptr *mp = this_cpu_ptr(pai_root[idx].mapptr);
struct pai_map *cpump = mp->mapptr;
/* Cope with multiple invocations:
* 1. perf_event_throttle() --> PMU->stop()
* 2. task schedules out --> PMU->stop()
* Check for event already stopped.
*/
if (event->hw.state & PERF_HES_STOPPED)
return;
if (!event->attr.sample_period) { /* Counting */
pai_pmu[idx].pmu->read(event);
} else { /* Sampling */
@ -672,9 +680,9 @@ static void pai_have_samples(int idx)
{
struct pai_mapptr *mp = this_cpu_ptr(pai_root[idx].mapptr);
struct pai_map *cpump = mp->mapptr;
struct perf_event *event;
struct perf_event *event, *e2;
list_for_each_entry(event, &cpump->syswide_list, hw.tp_list)
list_for_each_entry_safe(event, e2, &cpump->syswide_list, hw.tp_list)
pai_have_sample(event, cpump);
}
@ -691,6 +699,17 @@ static void paicrypt_sched_task(struct perf_event_pmu_context *pmu_ctx,
pai_have_samples(PAI_PMU_CRYPTO);
}
/* Prevent ioctl(fd, PERF_EVENT_IOC_PERIOD, ...) call.
* It sets perf_event::event_limit to a positive value and causes
* perf_event_overflow() to invoke pai_stop() call back function when
* perf_event::event_limit hits zero. This is not supported because the
* sample events CRYPTO_ALL and NNPA_ALL are always taken at schedule out
* of a task.
*/
static int pai_check_period(struct perf_event *event, u64 value)
{
return -EINVAL;
}
/* ============================= paiext ====================================*/
static void paiext_event_destroy(struct perf_event *event)
@ -804,6 +823,7 @@ static struct pmu paicrypt = {
.stop = paicrypt_stop,
.read = paicrypt_read,
.sched_task = paicrypt_sched_task,
.check_period = pai_check_period,
.attr_groups = paicrypt_attr_groups
};
@ -1015,6 +1035,7 @@ static struct pmu paiext = {
.stop = paiext_stop,
.read = paiext_read,
.sched_task = paiext_sched_task,
.check_period = pai_check_period,
.attr_groups = paiext_attr_groups,
};