Re: [PATCH] perf record: Skip affinity for per-thread mmap buffers

[sashiko-bot@kernel.org]

> From: Paul Moses <p@1g4.org>
> 
> Per-thread mmap buffers use CPU -1 to mean any CPU. Combining --per-thread
> with --affinity=cpu passes this value to __set_bit() when constructing the
> reader affinity mask, causing an out-of-bounds bitmap access and SIGSEGV.
> 
> Program received signal SIGSEGV, Segmentation fault.
> 0x0000555555f3488e in mmap.mmap ()
> #0  0x0000555555f3488e in mmap.mmap ()
> #1  0x0000555555e2f7bf in mmap_per_evsel (evlist=evlist@entry=0x7fffedcc1150, ops=ops@entry=0x7fffffffaf50, idx=idx@entry=0, mp=mp@entry=0x7fffffffaf70, cpu_idx=cpu_idx@entry=0, thread=thread@entry=0, _output=0x7fffffffaf08, _output_overwrite=0x7fffffffaf04, nr_mmaps=0x7fffffffaf0c) at evlist.c:598
> #2  0x0000555555e2ef96 in mmap_per_thread (evlist=0x7fffedcc1150, ops=0x7fffffffaf50, mp=0x7fffffffaf70) at evlist.c:650
> #3  perf_evlist__mmap_ops (evlist=0x7fffedcc1150, ops=0x7fffffffaf50, mp=0x7fffffffaf70) at evlist.c:748
> #4  0x0000555555f2150d in evlist.mmap_ex ()
> #5  0x0000555555db0b0a in record.open ()
> #6  0x0000555555dadea7 in __cmd_record ()
> [ ... ]
> nonnegative CPU. Skip the reader-side bitmap operations as well, since
> per-thread buffers no longer allocate an affinity mask.
> 
> Fixes: 8384a2600c7d ("perf record: Adapt affinity to machines with #CPUs > 1K")
> Signed-off-by: Paul Moses <p@1g4.org>

Sashiko has reviewed this patch and found no issues.

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