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Thu, 05 Mar 2026 06:02:00 -0800 (PST) From: Jiri Olsa X-Google-Original-From: Jiri Olsa Date: Thu, 5 Mar 2026 15:01:58 +0100 To: bot+bpf-ci@kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, bpf@vger.kernel.org, linux-trace-kernel@vger.kernel.org, kafai@fb.com, eddyz87@gmail.com, songliubraving@fb.com, yhs@fb.com, menglong8.dong@gmail.com, rostedt@kernel.org, martin.lau@kernel.org, yonghong.song@linux.dev, clm@meta.com, ihor.solodrai@linux.dev Subject: Re: [PATCHv2 bpf-next 02/23] bpf: Use mutex lock pool for bpf trampolines Message-ID: References: <20260304222141.497203-3-jolsa@kernel.org> <28376b19ac32833bc93e5688dbb271724f84f19aece2f828c7ca56bbd9706a0f@mail.kernel.org> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <28376b19ac32833bc93e5688dbb271724f84f19aece2f828c7ca56bbd9706a0f@mail.kernel.org> On Wed, Mar 04, 2026 at 11:02:28PM +0000, bot+bpf-ci@kernel.org wrote: > > diff --git a/kernel/bpf/trampoline.c b/kernel/bpf/trampoline.c > > --- a/kernel/bpf/trampoline.c > > +++ b/kernel/bpf/trampoline.c > > [ ... ] > > > @@ -99,12 +127,12 @@ static int bpf_tramp_ftrace_ops_func(struct ftrace_ops *ops, unsigned long ip, > > * cleanup_direct_functions_after_ipmodify > > * > > * In both cases, direct_mutex is already locked. Use > > - * mutex_trylock(&tr->mutex) to avoid deadlock in race condition > > + * mutex_trylock(select_trampoline_lock(tr)) to avoid deadlock in race condition > > * (something else is making changes to this same trampoline). > > */ > > - if (!mutex_trylock(&tr->mutex)) { > > - /* sleep 1 ms to make sure whatever holding tr->mutex makes > > - * some progress. > > + if (!mutex_trylock(select_trampoline_lock(tr))) { > > + /* sleep 1 ms to make sure whatever holding select_trampoline_lock(tr) > > + * makes some progress. > > */ > > With a pool of 32 mutexes, the trylock can now also fail because a > different trampoline that hashes to the same pool entry holds the lock. > Should the comment say "something else holds the same pool lock" instead > of "something else is making changes to this same trampoline"? right, will change the comment, thnx > > Similarly, the sleep comment says the holder "makes some progress" but > with a pool lock the holder could be operating on an entirely unrelated > trampoline. this one seems ok to me.. holder is 'whatever holding select_trampoline_lock' which is correct jirka > > > --- > AI reviewed your patch. Please fix the bug or email reply why it's not a bug. > See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md > > CI run summary: https://github.com/kernel-patches/bpf/actions/runs/22692622038