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perf/core: Fix the mlock accounting, again

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Commit:

  5e6c3c7b1e ("perf/aux: Fix tracking of auxiliary trace buffer allocation")

tried to guess the correct combination of arithmetic operations that would
undo the AUX buffer's mlock accounting, and failed, leaking the bottom part
when an allocation needs to be charged partially to both user->locked_vm
and mm->pinned_vm, eventually leaving the user with no locked bonus:

  $ perf record -e intel_pt//u -m1,128 uname
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.061 MB perf.data ]

  $ perf record -e intel_pt//u -m1,128 uname
  Permission error mapping pages.
  Consider increasing /proc/sys/kernel/perf_event_mlock_kb,
  or try again with a smaller value of -m/--mmap_pages.
  (current value: 1,128)

Fix this by subtracting both locked and pinned counts when AUX buffer is
unmapped.

Reported-by: Thomas Richter <[email protected]>
Tested-by: Thomas Richter <[email protected]>
Signed-off-by: Alexander Shishkin <[email protected]>
Acked-by: Peter Zijlstra <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Vince Weaver <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
This commit is contained in:
Alexander Shishkin
2019-11-18 16:27:37 +01:00
committed by Ingo Molnar
parent af42d3466b
commit 36b3db03b4
1 changed files with 2 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files
kernel/events/core.c
+2 -4
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@@ -5607,10 +5607,8 @@ static void perf_mmap_close(struct vm_area_struct *vma)
perf_pmu_output_stop(event);
/* now it's safe to free the pages */
if (!rb->aux_mmap_locked)
atomic_long_sub(rb->aux_nr_pages, &mmap_user->locked_vm);
else
atomic64_sub(rb->aux_mmap_locked, &vma->vm_mm->pinned_vm);
atomic_long_sub(rb->aux_nr_pages - rb->aux_mmap_locked, &mmap_user->locked_vm);
atomic64_sub(rb->aux_mmap_locked, &vma->vm_mm->pinned_vm);
/* this has to be the last one */
rb_free_aux(rb);