From: sashiko-bot@kernel.org
To: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
Cc: linux-perf-users@vger.kernel.org
Subject: Re: [PATCH bpf-next 5/9] uprobes: Don't sleep on mmap_lock under dup_mmap_sem
Date: Thu, 22 Oct 2026 02:16:56 +0000 [thread overview]
Message-ID: <sashiko-outbox-180862@kernel.org> (raw)
In-Reply-To: <20261022015712.1297331-6-alexei.starovoitov@gmail.com>
> From: Alexei Starovoitov <ast@kernel.org>
>
> register_for_each_vma() takes dup_mmap_sem for writing, collects mms that
> map the file and takes mmap_lock of every mm. fork() takes dup_mmap_sem for
> reading. When mmap_lock of one mm is busy every fork() in the system waits
> for it:
>
> A: mmap(MAP_POPULATE) -> mmap_read_lock(A)
> tracer: percpu_down_write(&dup_mmap_sem), mmap_write_lock(A) sleeps
> others: fork() -> percpu_down_read(&dup_mmap_sem) sleeps
>
> Only trylock mmap_lock under dup_mmap_sem. Leave mms with busy mmap_lock in
> the list, drop dup_mmap_sem and then wait for them.
>
> dup_mmap_sem makes sure that mm doesn't fork between build_map_info() and
> [ ... ]
>
> enable uprobe event 105 -> 205 201 -> 481 207 -> 784
> disable uprobe event 225 -> 294 354 -> 579 407 -> 893
>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261022015712.1297331-1-alexei.starovoitov@gmail.com?part=5
next prev parent reply other threads:[~2026-10-22 2:16 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-22 1:57 [PATCH bpf-next 0/9] uprobes: Don't stall fork() when mmap_lock is busy Alexei Starovoitov
2026-10-22 1:57 ` [PATCH bpf-next 1/9] mm: Bring back mmap_write_trylock() Alexei Starovoitov
2026-10-22 2:02 ` sashiko-bot
2026-10-22 1:57 ` [PATCH bpf-next 2/9] uprobes: Don't run exit_mmap() under dup_mmap_sem Alexei Starovoitov
2026-10-22 2:04 ` sashiko-bot
2026-10-22 1:57 ` [PATCH bpf-next 3/9] uprobes/x86: Finish an unoptimization which failed half-way Alexei Starovoitov
2026-10-22 2:06 ` sashiko-bot
2026-10-22 2:57 ` Gregory Price (Meta)
2026-10-22 1:57 ` [PATCH bpf-next 4/9] uprobes/x86: Don't WARN if an optimized probe can't be written Alexei Starovoitov
2026-10-22 2:03 ` sashiko-bot
2026-10-22 2:37 ` bot+bpf-ci
2026-10-22 17:56 ` Jann Horn
2026-10-22 19:33 ` Liam R. Howlett
2026-10-22 1:57 ` [PATCH bpf-next 5/9] uprobes: Don't sleep on mmap_lock under dup_mmap_sem Alexei Starovoitov
2026-10-22 2:16 ` sashiko-bot [this message]
2026-10-22 2:37 ` bot+bpf-ci
2026-10-22 23:11 ` Andrii Nakryiko
2026-10-22 1:57 ` [PATCH bpf-next 6/9] uprobes: Don't sleep on mmap_lock with dup_mmap_sem held in dup_mmap() Alexei Starovoitov
2026-10-22 2:15 ` sashiko-bot
2026-10-22 18:42 ` Jann Horn
2026-10-22 1:57 ` [PATCH bpf-next 7/9] fork: Let the new task point to its mm before uprobes can find it Alexei Starovoitov
2026-10-22 2:23 ` sashiko-bot
2026-10-22 1:57 ` [PATCH bpf-next 8/9] uprobes: Don't leak the breakpoints if the unregistering task is killed Alexei Starovoitov
2026-10-22 2:20 ` sashiko-bot
2026-10-22 1:57 ` [PATCH bpf-next 9/9] selftests/bpf: Test uprobes and fork() with busy mmap_lock Alexei Starovoitov
2026-10-22 2:10 ` sashiko-bot
2026-10-22 2:22 ` Alexei Starovoitov
2026-10-22 2:37 ` bot+bpf-ci
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