shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-05 18:41:58 +09:00
Code Issues Packages Projects Releases Wiki Activity

perf/x86/intel/pt: Fix sampling synchronization

Browse Source 
commit d92792a4b26e50b96ab734cbe203d8a4c932a7a9 upstream.

pt_event_snapshot_aux() uses pt->handle_nmi to determine if tracing
needs to be stopped, however tracing can still be going because
pt->handle_nmi is set to zero before tracing is stopped in pt_event_stop,
whereas pt_event_snapshot_aux() requires that tracing must be stopped in
order to copy a sample of trace from the buffer.

Instead call pt_config_stop() always, which anyway checks config for
RTIT_CTL_TRACEEN and does nothing if it is already clear.

Note pt_event_snapshot_aux() can continue to use pt->handle_nmi to
determine if the trace needs to be restarted afterwards.

Fixes: 25e8920b30 ("perf/x86/intel/pt: Add sampling support")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20240715160712.127117-2-adrian.hunter@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Adrian Hunter
2024-07-15 19:07:00 +03:00
committed by Greg Kroah-Hartman
parent 5b22c038fb
commit 89debcc2aa
1 changed files with 7 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
arch/x86/events/intel/pt.c
View File

@@ -1602,6 +1602,7 @@ static void pt_event_stop(struct perf_event *event, int mode)
* see comment in intel_pt_interrupt(). * see comment in intel_pt_interrupt().
*/ */
WRITE_ONCE(pt->handle_nmi, 0); WRITE_ONCE(pt->handle_nmi, 0);
barrier();
pt_config_stop(event); pt_config_stop(event);
@@ -1653,11 +1654,10 @@ static long pt_event_snapshot_aux(struct perf_event *event,
return 0; return 0;
/* /*
* Here, handle_nmi tells us if the tracing is on * There is no PT interrupt in this mode, so stop the trace and it will
* remain stopped while the buffer is copied.
*/ */
if (READ_ONCE(pt->handle_nmi)) pt_config_stop(event);
pt_config_stop(event);
pt_read_offset(buf); pt_read_offset(buf);
pt_update_head(pt); pt_update_head(pt);
@@ -1669,11 +1669,10 @@ static long pt_event_snapshot_aux(struct perf_event *event,
ret = perf_output_copy_aux(&pt->handle, handle, from, to); ret = perf_output_copy_aux(&pt->handle, handle, from, to);
/* /*
* If the tracing was on when we turned up, restart it. * Here, handle_nmi tells us if the tracing was on.
* Compiler barrier not needed as we couldn't have been * If the tracing was on, restart it.
* preempted by anything that touches pt->handle_nmi.
*/ */
if (pt->handle_nmi) if (READ_ONCE(pt->handle_nmi))
pt_config_start(event); pt_config_start(event);
return ret; return ret;