From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794001498; b=EWV5R0FlY8sdwwdAMlz7P6cF5M9tk1M2bCEoFweyZDHJa0X/GqNkKfIyK+TzthWCYjI0 5y1+SnhH11LDiWXznJRzEf11UOGtGdMWtY5NziE5Cw4ayc6ziUNJnfQt3hYXt43qLXQDw HUIE8RrFd/hXHlnMW+5+/dXysZ8fcJF16u6LUM3EJETsEtD1+/cJWysId8BxTuqkP4D0S yPnaBNYtWXU+E49LqE3bOKd+E1T7A0J1vMjDMZvpN7OYVSdpC/rQIFjLVCX/FIJP+CjaX 1OD+tJaIBp0FmjMpCw/YR96YAQcCTWGFcR/BSo5Vi8Fu3LUfZwBunstJalwpTR0z2UQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794001498; h=Received:DKIM-Signature:Date:From:To:Cc:Subject:Message-ID: References:MIME-Version:Content-Type:Content-Disposition:In-Reply-To; bh=o6y7zpd4HTLdQTePgJ7BQ9bAxgxtM6ve+DgOROkBU0g=; b=uZ5mteNaCPCrjCiBx13vEEFJXlIgx3JuPDEesUptCbaWyEVdpLTFK3jRBvBs+9wBGVL0 pUtS0MNvpizjUfIHd0814tS2AN9wtFw8yf91qD4x3tVLL3Pi3LwXHAuLAS+rLTYS007xh J3RY164Eo/LZimDmrX2ULV82YW4Gxe6JSrF7scMkyR5fh2VnkSl9lRrmvHP2arWiSVGVA Dkx53CzeKkOOfTLIYtI68JREYG0Gs3TX22i/UujcMMee4cXdeC7BwQJpKOzPPJdGQOr+G rJT9BZa7ru1eg2q8XTJDhF2VnC1+BVcPuu8NeXpHhwxTk4qztMUVrbxxvqDp3EZcHgg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=BrT78GB+; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3AF07606A326; Fri, 6 Nov 2026 21:44:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=BrT78GB+ Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0F62C1F0089F; Fri, 6 Nov 2026 21:44:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794001497; bh=o6y7zpd4HTLdQTePgJ7BQ9bAxgxtM6ve+DgOROkBU0g=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=BrT78GB+0O1hMds4+JN9Mq9eJhh/79yUOP/77xeG04uqM7Hkh81IVFN7oRZZW+IvU SvBeBW18uN6VuyAdnwSNNlLS5LIJG+f78+KnXpbyy66k1tZ3pwoEqsbdBOF2yJflVX 9ynwNOWm6Cj6Bl0YUJwQC69bzU6UORHYaZ/bo/COS/oI804EspBTSU1NTdFLVI9wXe AtqOvE3JnS68ngOtIoxCk9445DjfhbIlLQO0vjJSkAnB2a/b55hR2GmoTSZZL/zQ5g c5QWHcg31kYmtlONZ7mXGGXuRguXhXoN4y4XtIEUtZR5tG9kbIsmUklt5T47h2NfCi ZRiDhMkQOQ7zg== Date: Fri, 6 Nov 2026 13:44:54 -0800 From: Namhyung Kim To: Paul Moses , acme@kernel.org Cc: peterz@infradead.org, mingo@redhat.com, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, james.clark@linaro.org, alexey.budankov@linux.intel.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] perf record: Skip affinity for per-thread mmap buffers Message-ID: References: <20261030065857.2157899-1-p@1g4.org> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: On Fri, Nov 06, 2026 at 07:32:29AM +0000, Paul Moses wrote: > > > > > On Friday, November 6th, 2026 at 1:18 AM, Namhyung Kim wrote: > > > Hello, > > > > On Fri, Oct 30, 2026 at 06:59:28AM +0000, Paul wrote: > > > From: Paul Moses > > > > > > 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 > > > rax 0x7fffef9e9bd0 140737213537232 > > > rbx 0x7fffedd249a0 140737183369632 > > > rcx 0x3ffffffffffffff 288230376151711743 > > > rdx 0x8000000000000000 -9223372036854775808 > > > rsi 0x0 0 > > > rdi 0x7fffef9e9bd0 140737213537232 > > > 0x555555f34876 : movswq 0x10(%rbx),%rcx > > > 0x555555f3487b : mov 0xb8(%rbx),%rax > > > 0x555555f34882 : mov $0x1,%edx > > > 0x555555f34887 : shl %cl,%rdx > > > 0x555555f3488a : shr $0x6,%rcx > > > => 0x555555f3488e : or %rdx,(%rax,%rcx,8) > > > 0x555555f34892 : lea 0x17711b(%rip),%r14 # 0x5555560ab9b4 > > > 0x555555f34899 : cmpl $0x2,(%r14) > > > 0x555555f3489d : jne 0x555555f348f7 > > > 0x555555f3489f : mov 0xb8(%rbx),%rdi > > > 0x555555f348a6 : mov 0xc0(%rbx),%esi > > > 0x555555f348ac : 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 > > > --- > > > 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