* [PATCH] perf record: Skip affinity for per-thread mmap buffers
@ 2026-10-30 6:59 Paul
2026-10-30 7:06 ` sashiko-bot
2026-11-06 7:18 ` Namhyung Kim
0 siblings, 2 replies; 6+ messages in thread
From: Paul @ 2026-10-30 6:59 UTC (permalink / raw)
To: acme, namhyung
Cc: peterz, mingo, mark.rutland, alexander.shishkin, jolsa, irogers,
adrian.hunter, james.clark, alexey.budankov, linux-perf-users,
linux-kernel, Paul Moses
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 ()
#7 0x0000555555daca89 in cmd_record ()
#8 0x0000555555e27d53 in run_builtin ()
#9 0x0000555555e277cf in main ()
rip 0x555555f3488e 0x555555f3488e <mmap.mmap+382>
rax 0x7fffef9e9bd0 140737213537232
rbx 0x7fffedd249a0 140737183369632
rcx 0x3ffffffffffffff 288230376151711743
rdx 0x8000000000000000 -9223372036854775808
rsi 0x0 0
rdi 0x7fffef9e9bd0 140737213537232
0x555555f34876 <mmap__mmap+358>: movswq 0x10(%rbx),%rcx
0x555555f3487b <mmap__mmap+363>: mov 0xb8(%rbx),%rax
0x555555f34882 <mmap__mmap+370>: mov $0x1,%edx
0x555555f34887 <mmap__mmap+375>: shl %cl,%rdx
0x555555f3488a <mmap__mmap+378>: shr $0x6,%rcx
=> 0x555555f3488e <mmap__mmap+382>: or %rdx,(%rax,%rcx,8)
0x555555f34892 <mmap__mmap+386>: lea 0x17711b(%rip),%r14 # 0x5555560ab9b4 <verbose>
0x555555f34899 <mmap__mmap+393>: cmpl $0x2,(%r14)
0x555555f3489d <mmap__mmap+397>: jne 0x555555f348f7 <mmap__mmap+487>
0x555555f3489f <mmap__mmap+399>: mov 0xb8(%rbx),%rdi
0x555555f348a6 <mmap__mmap+406>: mov 0xc0(%rbx),%esi
0x555555f348ac <mmap__mmap+412>: lea -0x430(%rbp),%r12
Only construct and apply reader affinity masks for buffers with a
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>
---
tools/perf/builtin-record.c | 2 +-
tools/perf/util/mmap.c | 4 ++--
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index a57987851cf0..d7c8f490cb62 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1565,7 +1565,7 @@ static struct perf_event_header finished_init_event = {
static void record__adjust_affinity(struct record *rec, struct mmap *map)
{
- if (rec->opts.affinity != PERF_AFFINITY_SYS &&
+ if (map->core.cpu.cpu >= 0 && rec->opts.affinity != PERF_AFFINITY_SYS &&
!bitmap_equal(thread->mask->affinity.bits, map->affinity_mask.bits,
thread->mask->affinity.nbits)) {
bitmap_zero(thread->mask->affinity.bits, thread->mask->affinity.nbits);
diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
index 358e70c4f3ed..be3dffdaede8 100644
--- a/tools/perf/util/mmap.c
+++ b/tools/perf/util/mmap.c
@@ -292,8 +292,8 @@ int mmap__mmap(struct mmap *map, struct mmap_params *mp, int fd, struct perf_cpu
return -1;
}
- if (mp->affinity != PERF_AFFINITY_SYS &&
- perf_mmap__setup_affinity_mask(map, mp)) {
+ if (cpu.cpu >= 0 && mp->affinity != PERF_AFFINITY_SYS &&
+ perf_mmap__setup_affinity_mask(map, mp)) {
pr_debug2("failed to alloc mmap affinity mask, error %d\n",
errno);
return -1;
--
2.56.GIT
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH] perf record: Skip affinity for per-thread mmap buffers
2026-10-30 6:59 [PATCH] perf record: Skip affinity for per-thread mmap buffers Paul
@ 2026-10-30 7:06 ` sashiko-bot
2026-11-06 7:18 ` Namhyung Kim
1 sibling, 0 replies; 6+ messages in thread
From: sashiko-bot @ 2026-10-30 7:06 UTC (permalink / raw)
To: Paul; +Cc: linux-perf-users
> 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.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261030065857.2157899-1-p@1g4.org?part=1
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] perf record: Skip affinity for per-thread mmap buffers
2026-10-30 6:59 [PATCH] perf record: Skip affinity for per-thread mmap buffers Paul
2026-10-30 7:06 ` sashiko-bot
@ 2026-11-06 7:18 ` Namhyung Kim
2026-11-06 7:32 ` Paul Moses
1 sibling, 1 reply; 6+ messages in thread
From: Namhyung Kim @ 2026-11-06 7:18 UTC (permalink / raw)
To: Paul
Cc: acme, peterz, mingo, mark.rutland, alexander.shishkin, jolsa,
irogers, adrian.hunter, james.clark, alexey.budankov,
linux-perf-users, linux-kernel
Hello,
On Fri, Oct 30, 2026 at 06:59:28AM +0000, Paul wrote:
> 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 ()
> #7 0x0000555555daca89 in cmd_record ()
> #8 0x0000555555e27d53 in run_builtin ()
> #9 0x0000555555e277cf in main ()
Please indent terminal outpus otherwise git will eat up lines start with
the hash (#).
> rip 0x555555f3488e 0x555555f3488e <mmap.mmap+382>
> rax 0x7fffef9e9bd0 140737213537232
> rbx 0x7fffedd249a0 140737183369632
> rcx 0x3ffffffffffffff 288230376151711743
> rdx 0x8000000000000000 -9223372036854775808
> rsi 0x0 0
> rdi 0x7fffef9e9bd0 140737213537232
> 0x555555f34876 <mmap__mmap+358>: movswq 0x10(%rbx),%rcx
> 0x555555f3487b <mmap__mmap+363>: mov 0xb8(%rbx),%rax
> 0x555555f34882 <mmap__mmap+370>: mov $0x1,%edx
> 0x555555f34887 <mmap__mmap+375>: shl %cl,%rdx
> 0x555555f3488a <mmap__mmap+378>: shr $0x6,%rcx
> => 0x555555f3488e <mmap__mmap+382>: or %rdx,(%rax,%rcx,8)
> 0x555555f34892 <mmap__mmap+386>: lea 0x17711b(%rip),%r14 # 0x5555560ab9b4 <verbose>
> 0x555555f34899 <mmap__mmap+393>: cmpl $0x2,(%r14)
> 0x555555f3489d <mmap__mmap+397>: jne 0x555555f348f7 <mmap__mmap+487>
> 0x555555f3489f <mmap__mmap+399>: mov 0xb8(%rbx),%rdi
> 0x555555f348a6 <mmap__mmap+406>: mov 0xc0(%rbx),%esi
> 0x555555f348ac <mmap__mmap+412>: lea -0x430(%rbp),%r12
>
> Only construct and apply reader affinity masks for buffers with a
> nonnegative CPU. Skip the reader-side bitmap operations as well, since
> per-thread buffers no longer allocate an affinity mask.
Maybe we can just reject those options when they are used together.
Thanks,
Namhyung
>
> Fixes: 8384a2600c7d ("perf record: Adapt affinity to machines with #CPUs > 1K")
> Signed-off-by: Paul Moses <p@1g4.org>
> ---
> tools/perf/builtin-record.c | 2 +-
> tools/perf/util/mmap.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> index a57987851cf0..d7c8f490cb62 100644
> --- a/tools/perf/builtin-record.c
> +++ b/tools/perf/builtin-record.c
> @@ -1565,7 +1565,7 @@ static struct perf_event_header finished_init_event = {
>
> static void record__adjust_affinity(struct record *rec, struct mmap *map)
> {
> - if (rec->opts.affinity != PERF_AFFINITY_SYS &&
> + if (map->core.cpu.cpu >= 0 && rec->opts.affinity != PERF_AFFINITY_SYS &&
> !bitmap_equal(thread->mask->affinity.bits, map->affinity_mask.bits,
> thread->mask->affinity.nbits)) {
> bitmap_zero(thread->mask->affinity.bits, thread->mask->affinity.nbits);
> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> index 358e70c4f3ed..be3dffdaede8 100644
> --- a/tools/perf/util/mmap.c
> +++ b/tools/perf/util/mmap.c
> @@ -292,8 +292,8 @@ int mmap__mmap(struct mmap *map, struct mmap_params *mp, int fd, struct perf_cpu
> return -1;
> }
>
> - if (mp->affinity != PERF_AFFINITY_SYS &&
> - perf_mmap__setup_affinity_mask(map, mp)) {
> + if (cpu.cpu >= 0 && mp->affinity != PERF_AFFINITY_SYS &&
> + perf_mmap__setup_affinity_mask(map, mp)) {
> pr_debug2("failed to alloc mmap affinity mask, error %d\n",
> errno);
> return -1;
> --
> 2.56.GIT
>
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] perf record: Skip affinity for per-thread mmap buffers
2026-11-06 7:18 ` Namhyung Kim
@ 2026-11-06 7:32 ` Paul Moses
2026-11-06 21:44 ` Namhyung Kim
0 siblings, 1 reply; 6+ messages in thread
From: Paul Moses @ 2026-11-06 7:32 UTC (permalink / raw)
To: Namhyung Kim
Cc: acme, peterz, mingo, mark.rutland, alexander.shishkin, jolsa,
irogers, adrian.hunter, james.clark, alexey.budankov,
linux-perf-users, linux-kernel
On Friday, November 6th, 2026 at 1:18 AM, Namhyung Kim <namhyung@kernel.org> wrote:
> Hello,
>
> On Fri, Oct 30, 2026 at 06:59:28AM +0000, Paul wrote:
> > 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 ()
> > #7 0x0000555555daca89 in cmd_record ()
> > #8 0x0000555555e27d53 in run_builtin ()
> > #9 0x0000555555e277cf in main ()
>
> Please indent terminal outpus otherwise git will eat up lines start with
> the hash (#).
>
> > rip 0x555555f3488e 0x555555f3488e <mmap.mmap+382>
> > rax 0x7fffef9e9bd0 140737213537232
> > rbx 0x7fffedd249a0 140737183369632
> > rcx 0x3ffffffffffffff 288230376151711743
> > rdx 0x8000000000000000 -9223372036854775808
> > rsi 0x0 0
> > rdi 0x7fffef9e9bd0 140737213537232
> > 0x555555f34876 <mmap__mmap+358>: movswq 0x10(%rbx),%rcx
> > 0x555555f3487b <mmap__mmap+363>: mov 0xb8(%rbx),%rax
> > 0x555555f34882 <mmap__mmap+370>: mov $0x1,%edx
> > 0x555555f34887 <mmap__mmap+375>: shl %cl,%rdx
> > 0x555555f3488a <mmap__mmap+378>: shr $0x6,%rcx
> > => 0x555555f3488e <mmap__mmap+382>: or %rdx,(%rax,%rcx,8)
> > 0x555555f34892 <mmap__mmap+386>: lea 0x17711b(%rip),%r14 # 0x5555560ab9b4 <verbose>
> > 0x555555f34899 <mmap__mmap+393>: cmpl $0x2,(%r14)
> > 0x555555f3489d <mmap__mmap+397>: jne 0x555555f348f7 <mmap__mmap+487>
> > 0x555555f3489f <mmap__mmap+399>: mov 0xb8(%rbx),%rdi
> > 0x555555f348a6 <mmap__mmap+406>: mov 0xc0(%rbx),%esi
> > 0x555555f348ac <mmap__mmap+412>: lea -0x430(%rbp),%r12
> >
> > Only construct and apply reader affinity masks for buffers with a
> > nonnegative CPU. Skip the reader-side bitmap operations as well, since
> > per-thread buffers no longer allocate an affinity mask.
>
> Maybe we can just reject those options when they are used together.
>
> Thanks,
> Namhyung
>
> >
> > Fixes: 8384a2600c7d ("perf record: Adapt affinity to machines with #CPUs > 1K")
> > Signed-off-by: Paul Moses <p@1g4.org>
> > ---
> > tools/perf/builtin-record.c | 2 +-
> > tools/perf/util/mmap.c | 4 ++--
> > 2 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > index a57987851cf0..d7c8f490cb62 100644
> > --- a/tools/perf/builtin-record.c
> > +++ b/tools/perf/builtin-record.c
> > @@ -1565,7 +1565,7 @@ static struct perf_event_header finished_init_event = {
> >
> > static void record__adjust_affinity(struct record *rec, struct mmap *map)
> > {
> > - if (rec->opts.affinity != PERF_AFFINITY_SYS &&
> > + if (map->core.cpu.cpu >= 0 && rec->opts.affinity != PERF_AFFINITY_SYS &&
> > !bitmap_equal(thread->mask->affinity.bits, map->affinity_mask.bits,
> > thread->mask->affinity.nbits)) {
> > bitmap_zero(thread->mask->affinity.bits, thread->mask->affinity.nbits);
> > diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> > index 358e70c4f3ed..be3dffdaede8 100644
> > --- a/tools/perf/util/mmap.c
> > +++ b/tools/perf/util/mmap.c
> > @@ -292,8 +292,8 @@ int mmap__mmap(struct mmap *map, struct mmap_params *mp, int fd, struct perf_cpu
> > return -1;
> > }
> >
> > - if (mp->affinity != PERF_AFFINITY_SYS &&
> > - perf_mmap__setup_affinity_mask(map, mp)) {
> > + if (cpu.cpu >= 0 && mp->affinity != PERF_AFFINITY_SYS &&
> > + perf_mmap__setup_affinity_mask(map, mp)) {
> > pr_debug2("failed to alloc mmap affinity mask, error %d\n",
> > errno);
> > return -1;
> > --
> > 2.56.GIT
> >
> >
>
Hi Namhyung,
Can we please get this one settled first. There have been issues
with important patches being overlooked for months.
https://lore.kernel.org/linux-perf-users/20261020171946.3593127-1-p@1g4.org/
Thanks
Paul
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] perf record: Skip affinity for per-thread mmap buffers
2026-11-06 7:32 ` Paul Moses
@ 2026-11-06 21:44 ` Namhyung Kim
2026-11-09 17:34 ` Arnaldo Carvalho de Melo
0 siblings, 1 reply; 6+ messages in thread
From: Namhyung Kim @ 2026-11-06 21:44 UTC (permalink / raw)
To: Paul Moses, acme
Cc: peterz, mingo, mark.rutland, alexander.shishkin, jolsa, irogers,
adrian.hunter, james.clark, alexey.budankov, linux-perf-users,
linux-kernel
On Fri, Nov 06, 2026 at 07:32:29AM +0000, Paul Moses wrote:
>
>
>
>
> On Friday, November 6th, 2026 at 1:18 AM, Namhyung Kim <namhyung@kernel.org> wrote:
>
> > Hello,
> >
> > On Fri, Oct 30, 2026 at 06:59:28AM +0000, Paul wrote:
> > > 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 ()
> > > #7 0x0000555555daca89 in cmd_record ()
> > > #8 0x0000555555e27d53 in run_builtin ()
> > > #9 0x0000555555e277cf in main ()
> >
> > Please indent terminal outpus otherwise git will eat up lines start with
> > the hash (#).
> >
> > > rip 0x555555f3488e 0x555555f3488e <mmap.mmap+382>
> > > rax 0x7fffef9e9bd0 140737213537232
> > > rbx 0x7fffedd249a0 140737183369632
> > > rcx 0x3ffffffffffffff 288230376151711743
> > > rdx 0x8000000000000000 -9223372036854775808
> > > rsi 0x0 0
> > > rdi 0x7fffef9e9bd0 140737213537232
> > > 0x555555f34876 <mmap__mmap+358>: movswq 0x10(%rbx),%rcx
> > > 0x555555f3487b <mmap__mmap+363>: mov 0xb8(%rbx),%rax
> > > 0x555555f34882 <mmap__mmap+370>: mov $0x1,%edx
> > > 0x555555f34887 <mmap__mmap+375>: shl %cl,%rdx
> > > 0x555555f3488a <mmap__mmap+378>: shr $0x6,%rcx
> > > => 0x555555f3488e <mmap__mmap+382>: or %rdx,(%rax,%rcx,8)
> > > 0x555555f34892 <mmap__mmap+386>: lea 0x17711b(%rip),%r14 # 0x5555560ab9b4 <verbose>
> > > 0x555555f34899 <mmap__mmap+393>: cmpl $0x2,(%r14)
> > > 0x555555f3489d <mmap__mmap+397>: jne 0x555555f348f7 <mmap__mmap+487>
> > > 0x555555f3489f <mmap__mmap+399>: mov 0xb8(%rbx),%rdi
> > > 0x555555f348a6 <mmap__mmap+406>: mov 0xc0(%rbx),%esi
> > > 0x555555f348ac <mmap__mmap+412>: lea -0x430(%rbp),%r12
> > >
> > > Only construct and apply reader affinity masks for buffers with a
> > > nonnegative CPU. Skip the reader-side bitmap operations as well, since
> > > per-thread buffers no longer allocate an affinity mask.
> >
> > Maybe we can just reject those options when they are used together.
> >
> > Thanks,
> > Namhyung
> >
> > >
> > > Fixes: 8384a2600c7d ("perf record: Adapt affinity to machines with #CPUs > 1K")
> > > Signed-off-by: Paul Moses <p@1g4.org>
> > > ---
> > > tools/perf/builtin-record.c | 2 +-
> > > tools/perf/util/mmap.c | 4 ++--
> > > 2 files changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > > index a57987851cf0..d7c8f490cb62 100644
> > > --- a/tools/perf/builtin-record.c
> > > +++ b/tools/perf/builtin-record.c
> > > @@ -1565,7 +1565,7 @@ static struct perf_event_header finished_init_event = {
> > >
> > > static void record__adjust_affinity(struct record *rec, struct mmap *map)
> > > {
> > > - if (rec->opts.affinity != PERF_AFFINITY_SYS &&
> > > + if (map->core.cpu.cpu >= 0 && rec->opts.affinity != PERF_AFFINITY_SYS &&
> > > !bitmap_equal(thread->mask->affinity.bits, map->affinity_mask.bits,
> > > thread->mask->affinity.nbits)) {
> > > bitmap_zero(thread->mask->affinity.bits, thread->mask->affinity.nbits);
> > > diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> > > index 358e70c4f3ed..be3dffdaede8 100644
> > > --- a/tools/perf/util/mmap.c
> > > +++ b/tools/perf/util/mmap.c
> > > @@ -292,8 +292,8 @@ int mmap__mmap(struct mmap *map, struct mmap_params *mp, int fd, struct perf_cpu
> > > return -1;
> > > }
> > >
> > > - if (mp->affinity != PERF_AFFINITY_SYS &&
> > > - perf_mmap__setup_affinity_mask(map, mp)) {
> > > + if (cpu.cpu >= 0 && mp->affinity != PERF_AFFINITY_SYS &&
> > > + perf_mmap__setup_affinity_mask(map, mp)) {
> > > pr_debug2("failed to alloc mmap affinity mask, error %d\n",
> > > errno);
> > > return -1;
> > > --
> > > 2.56.GIT
> > >
> > >
> >
>
>
> Hi Namhyung,
>
> Can we please get this one settled first. There have been issues
> with important patches being overlooked for months.
>
> https://lore.kernel.org/linux-perf-users/20261020171946.3593127-1-p@1g4.org/
Sorry about the delay. But please understand that there can be some
delays during a merge window. I'll take a look at the link but you
can ping me if it takes too long.
Arnaldo, I think it's simple enough to go to v7.4.
Thanks,
Namhyung
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] perf record: Skip affinity for per-thread mmap buffers
2026-11-06 21:44 ` Namhyung Kim
@ 2026-11-09 17:34 ` Arnaldo Carvalho de Melo
0 siblings, 0 replies; 6+ messages in thread
From: Arnaldo Carvalho de Melo @ 2026-11-09 17:34 UTC (permalink / raw)
To: Namhyung Kim
Cc: Paul Moses, peterz, mingo, mark.rutland, alexander.shishkin,
jolsa, irogers, adrian.hunter, james.clark, alexey.budankov,
linux-perf-users, linux-kernel
On Fri, Nov 06, 2026 at 01:44:54PM -0800, Namhyung Kim wrote:
> On Fri, Nov 06, 2026 at 07:32:29AM +0000, Paul Moses wrote:
> > On Friday, November 6th, 2026 at 1:18 AM, Namhyung Kim <namhyung@kernel.org> wrote:
> > >
> > > On Fri, Oct 30, 2026 at 06:59:28AM +0000, Paul wrote:
> > > > 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 ()
> > > > #7 0x0000555555daca89 in cmd_record ()
> > > > #8 0x0000555555e27d53 in run_builtin ()
> > > > #9 0x0000555555e277cf in main ()
> > >
> > > Please indent terminal outpus otherwise git will eat up lines start with
> > > the hash (#).
> > >
> > > > rip 0x555555f3488e 0x555555f3488e <mmap.mmap+382>
> > > > rax 0x7fffef9e9bd0 140737213537232
> > > > rbx 0x7fffedd249a0 140737183369632
> > > > rcx 0x3ffffffffffffff 288230376151711743
> > > > rdx 0x8000000000000000 -9223372036854775808
> > > > rsi 0x0 0
> > > > rdi 0x7fffef9e9bd0 140737213537232
> > > > 0x555555f34876 <mmap__mmap+358>: movswq 0x10(%rbx),%rcx
> > > > 0x555555f3487b <mmap__mmap+363>: mov 0xb8(%rbx),%rax
> > > > 0x555555f34882 <mmap__mmap+370>: mov $0x1,%edx
> > > > 0x555555f34887 <mmap__mmap+375>: shl %cl,%rdx
> > > > 0x555555f3488a <mmap__mmap+378>: shr $0x6,%rcx
> > > > => 0x555555f3488e <mmap__mmap+382>: or %rdx,(%rax,%rcx,8)
> > > > 0x555555f34892 <mmap__mmap+386>: lea 0x17711b(%rip),%r14 # 0x5555560ab9b4 <verbose>
> > > > 0x555555f34899 <mmap__mmap+393>: cmpl $0x2,(%r14)
> > > > 0x555555f3489d <mmap__mmap+397>: jne 0x555555f348f7 <mmap__mmap+487>
> > > > 0x555555f3489f <mmap__mmap+399>: mov 0xb8(%rbx),%rdi
> > > > 0x555555f348a6 <mmap__mmap+406>: mov 0xc0(%rbx),%esi
> > > > 0x555555f348ac <mmap__mmap+412>: lea -0x430(%rbp),%r12
> > > >
> > > > Only construct and apply reader affinity masks for buffers with a
> > > > nonnegative CPU. Skip the reader-side bitmap operations as well, since
> > > > per-thread buffers no longer allocate an affinity mask.
> > >
> > > Maybe we can just reject those options when they are used together.
> > >
> > > Thanks,
> > > Namhyung
> > >
> > > >
> > > > Fixes: 8384a2600c7d ("perf record: Adapt affinity to machines with #CPUs > 1K")
> > > > Signed-off-by: Paul Moses <p@1g4.org>
> > > > ---
> > > > tools/perf/builtin-record.c | 2 +-
> > > > tools/perf/util/mmap.c | 4 ++--
> > > > 2 files changed, 3 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
> > > > index a57987851cf0..d7c8f490cb62 100644
> > > > --- a/tools/perf/builtin-record.c
> > > > +++ b/tools/perf/builtin-record.c
> > > > @@ -1565,7 +1565,7 @@ static struct perf_event_header finished_init_event = {
> > > >
> > > > static void record__adjust_affinity(struct record *rec, struct mmap *map)
> > > > {
> > > > - if (rec->opts.affinity != PERF_AFFINITY_SYS &&
> > > > + if (map->core.cpu.cpu >= 0 && rec->opts.affinity != PERF_AFFINITY_SYS &&
> > > > !bitmap_equal(thread->mask->affinity.bits, map->affinity_mask.bits,
> > > > thread->mask->affinity.nbits)) {
> > > > bitmap_zero(thread->mask->affinity.bits, thread->mask->affinity.nbits);
> > > > diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> > > > index 358e70c4f3ed..be3dffdaede8 100644
> > > > --- a/tools/perf/util/mmap.c
> > > > +++ b/tools/perf/util/mmap.c
> > > > @@ -292,8 +292,8 @@ int mmap__mmap(struct mmap *map, struct mmap_params *mp, int fd, struct perf_cpu
> > > > return -1;
> > > > }
> > > >
> > > > - if (mp->affinity != PERF_AFFINITY_SYS &&
> > > > - perf_mmap__setup_affinity_mask(map, mp)) {
> > > > + if (cpu.cpu >= 0 && mp->affinity != PERF_AFFINITY_SYS &&
> > > > + perf_mmap__setup_affinity_mask(map, mp)) {
> > > > pr_debug2("failed to alloc mmap affinity mask, error %d\n",
> > > > errno);
> > > > return -1;
> > Hi Namhyung,
> >
> > Can we please get this one settled first. There have been issues
> > with important patches being overlooked for months.
> >
> > https://lore.kernel.org/linux-perf-users/20261020171946.3593127-1-p@1g4.org/
>
> Sorry about the delay. But please understand that there can be some
> delays during a merge window. I'll take a look at the link but you
> can ping me if it takes too long.
>
> Arnaldo, I think it's simple enough to go to v7.4.
Sure, I'LL process it, just looked and on only this other one:
https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools.git/commit/?h=perf-tools&id=82b4a28e758816365405e01d9ed09027d13ef77a
From Paul is in perf-tools for v7.4, should be in linux-next for some
days, Look at the pair of additional fixes from him,
- Arnaldo
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-11-09 17:35 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-10-30 6:59 [PATCH] perf record: Skip affinity for per-thread mmap buffers Paul
2026-10-30 7:06 ` sashiko-bot
2026-11-06 7:18 ` Namhyung Kim
2026-11-06 7:32 ` Paul Moses
2026-11-06 21:44 ` Namhyung Kim
2026-11-09 17:34 ` Arnaldo Carvalho de Melo
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