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[71.34.16.191]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-4afe2200c91sm1914434fac.4.2026.11.13.12.23.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Nov 2026 12:23:16 -0800 (PST) Message-ID: Subject: Re: [PATCH v7 05/10] tracing/osnoise: Per-cpu mutexes and fd detachment From: Crystal Wood To: sashiko-reviews@lists.linux.dev Cc: linux-trace-kernel@vger.kernel.org Date: Fri, 13 Nov 2026 14:23:15 -0600 In-Reply-To: References: <20261113064103.3041704-1-crwood@redhat.com> <20261113064103.3041704-6-crwood@redhat.com> User-Agent: Evolution 3.60.2 (3.60.2-3.fc44) X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 4g3p__FiCSC88VMS5feDYEtl3mqpQ6fi29m6sUIrqr0_1794601397 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Fri, 2026-11-13 at 07:14 +0000, sashiko-bot@kernel.org wrote: > Thank you for your contribution! Sashiko AI review found 1 potential > issue to consider: > - [Medium] tracing/osnoise: missing migration detection in > timerlat_fd_read() > -- >=20 > commit d34bc9208d90b4be9c903307f53e72248c2ac3b7 > Author: Crystal Wood >=20 > tracing/osnoise: Per-cpu mutexes and fd detachment >=20 > This commit introduces per-cpu mutexes to protect kthread and timerlat fi= le > descriptor state, replacing the SIGKILL mechanism for user-space timerlat > threads with a mutex-protected detachment mechanism. >=20 > [Severity: Medium] > In kernel/trace/trace_osnoise.c, timerlat_fd_read() removes the > cpu !=3D smp_processor_id() migration handling (which set > cpu_tmr_var(cpu)->uthread_migrate =3D 1, tainted osnoise, and stopped > tracing) and instead locks this_cpu_tmr_var()->detach_lock before checkin= g > fdd !=3D osn_var->fdd or tlat->uthread_migrate. >=20 > Can this miss user-space thread migrations when NO_OSNOISE_WORKLOAD is > enabled after the timerlat tracer has already been started? >=20 > By default, OSN_WORKLOAD is set in osnoise_options. If the user enables > timerlat first and then writes NO_OSNOISE_WORKLOAD to osnoise/options (as > shown in Documentation/trace/timerlat-tracer.rst), osnoise_options_write(= ) > does not call register_migration_monitor(), which only runs during initia= l > tracer startup in osnoise_workload_start() -> osnoise_hook_events() -> > hook_thread_events() -> register_migration_monitor() and skips registerin= g > trace_sched_migrate_callback() when OSN_WORKLOAD is set. That's a minor pre-existing bug that shouldn't block this patchset. -Crystal