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[108.212.132.20]) by smtp.gmail.com with ESMTPSA id 006d021491bc7-67bb3bb67fbsm2639289eaf.15.2026.03.09.14.27.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Mar 2026 14:27:32 -0700 (PDT) From: Wesley Atwell To: rostedt@goodmis.org Cc: mhiramat@kernel.org, mark.rutland@arm.com, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Wesley Atwell Subject: [PATCH v2 2/2] tracing: drain deferred trigger frees if kthread startup fails Date: Mon, 9 Mar 2026 15:27:02 -0600 Message-Id: <20260309212702.13622-3-atwellwea@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260309212702.13622-1-atwellwea@gmail.com> References: <20260309212702.13622-1-atwellwea@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Boot-time trigger registration can fail before the trigger-data cleanup kthread exists. Deferring those frees until late init is fine, but the post-boot fallback must still drain the deferred list if kthread creation never succeeds. Otherwise, boot-deferred nodes can accumulate on trigger_data_free_list, later frees fall back to synchronously freeing only the current object, and the older queued entries are leaked forever. Keep the deferred boot-time behavior, but when kthread creation fails, drain the whole queued list synchronously. Do the same in the late-init drain path so queued entries are not stranded there either. Fixes: 61d445af0a7c ("tracing: Add bulk garbage collection of freeing event= _trigger_data") Signed-off-by: Wesley Atwell --- v2: - Restore the dropped mutex recheck comment - Clarify the synchronous fallback drain path kernel/trace/trace_events_trigger.c | 79 ++++++++++++++++++++++++----- 1 file changed, 66 insertions(+), 13 deletions(-) diff --git a/kernel/trace/trace_events_trigger.c b/kernel/trace/trace_event= s_trigger.c index d5230b759a2d..428b46272ac8 100644 --- a/kernel/trace/trace_events_trigger.c +++ b/kernel/trace/trace_events_trigger.c @@ -22,6 +22,39 @@ static struct task_struct *trigger_kthread; static struct llist_head trigger_data_free_list; static DEFINE_MUTEX(trigger_data_kthread_mutex); =20 +static int trigger_kthread_fn(void *ignore); + +static void trigger_start_kthread_locked(void) +{ + lockdep_assert_held(&trigger_data_kthread_mutex); + + if (!trigger_kthread) { + struct task_struct *kthread; + + kthread =3D kthread_create(trigger_kthread_fn, NULL, + "trigger_data_free"); + if (!IS_ERR(kthread)) + WRITE_ONCE(trigger_kthread, kthread); + } +} + +static void trigger_data_free_queued_locked(void) +{ + struct event_trigger_data *data, *tmp; + struct llist_node *llnodes; + + lockdep_assert_held(&trigger_data_kthread_mutex); + + llnodes =3D llist_del_all(&trigger_data_free_list); + if (!llnodes) + return; + + tracepoint_synchronize_unregister(); + + llist_for_each_entry_safe(data, tmp, llnodes, llist) + kfree(data); +} + /* Bulk garbage collection of event_trigger_data elements */ static int trigger_kthread_fn(void *ignore) { @@ -56,30 +89,50 @@ void trigger_data_free(struct event_trigger_data *data) if (data->cmd_ops->set_filter) data->cmd_ops->set_filter(NULL, data, NULL); =20 + /* + * Boot-time trigger registration can fail before kthread creation + * works. Keep the deferred-free semantics during boot and let late + * init start the kthread to drain the list. + */ + if (system_state =3D=3D SYSTEM_BOOTING && !trigger_kthread) { + llist_add(&data->llist, &trigger_data_free_list); + return; + } + if (unlikely(!trigger_kthread)) { guard(mutex)(&trigger_data_kthread_mutex); + + trigger_start_kthread_locked(); /* Check again after taking mutex */ if (!trigger_kthread) { - struct task_struct *kthread; - - kthread =3D kthread_create(trigger_kthread_fn, NULL, - "trigger_data_free"); - if (!IS_ERR(kthread)) - WRITE_ONCE(trigger_kthread, kthread); + llist_add(&data->llist, &trigger_data_free_list); + /* Drain the queued frees synchronously if startup failed. */ + trigger_data_free_queued_locked(); + return; } } =20 - if (!trigger_kthread) { - /* Do it the slow way */ - tracepoint_synchronize_unregister(); - kfree(data); - return; - } - llist_add(&data->llist, &trigger_data_free_list); wake_up_process(trigger_kthread); } =20 +static int __init trigger_data_free_init(void) +{ + guard(mutex)(&trigger_data_kthread_mutex); + + if (llist_empty(&trigger_data_free_list)) + return 0; + + trigger_start_kthread_locked(); + if (trigger_kthread) + wake_up_process(trigger_kthread); + else + trigger_data_free_queued_locked(); + + return 0; +} +late_initcall(trigger_data_free_init); + static inline void data_ops_trigger(struct event_trigger_data *data, struct trace_buffer *buffer, void *rec, struct ring_buffer_event *event) --=20 2.34.1