From nobody Tue Feb 10 12:43:06 2026 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1BA8332E146; Wed, 7 Jan 2026 14:46:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767797170; cv=none; b=fa0S3wkUqL8tikdFLq8AR5Uzjq49IY/SGIqQznv9qzxlm7SjWyznFOoVYcQoJKs+ZUtjIOyV4sJtMFFOT9bRkoyHvlzdOyl0PGEduoovoRq+int+B2A13Eeb84T5/4Q9Li62PIhGefZ/VPImyt6qfO73shGTROgWxAJiAoxGIYE= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1767797170; c=relaxed/simple; bh=/0PDR36dqC9wzWmvey0pigsToRSURj9qy0p8V5fwbNg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=tn105CpPjerAgk+Si+kVsd1Ya0qAVscxy8Zez2tq/9p7zi0/5Q05FK0QX4VR8t8rstIolStxLPxZQMxm7fKzL7ngyl5K9gcJ+/YZAnIHCKCyIUYsMtWSqbMMh4d+GCEj/BWLyrHqbdrNqGR/fUXJX3RytEMFFDrBpVAdt7QtLQI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=K7eit0Xv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="K7eit0Xv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C8818C4CEF1; Wed, 7 Jan 2026 14:46:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1767797169; bh=/0PDR36dqC9wzWmvey0pigsToRSURj9qy0p8V5fwbNg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=K7eit0Xvz8Scor6fUi3/lZkvpZ5IHJDnpR6NnE4MEejVoRh14PdJZryCKfKp3ICdH Ihy3OvzdTLuqifMdqO69mkqMdetEIKgsB0kzC1Y2Hjm2t8HR8/miY42fTqx7jT8uQQ cfJmaI8chbQKiBE5AMqqlpOumAmmmGRfraOq+D51nspDTS8H1ik6NgSxF2nnVWwbkT AbiGLLuv00S2/BaheOhDgyR8P3ROw7+iPehq3l+nzD1Vh1V82whg4dQwe5IULB4opQ RlBvCECNDugzTiKGZCBM5VHi3Gk1paGVweC7/7Jj38SmxVH+1rwW3pURGhYH90fzHl 3VRiO6m7lad6w== From: "Masami Hiramatsu (Google)" To: Steven Rostedt Cc: Masami Hiramatsu , Mathieu Desnoyers , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH 2/2] tracing: Add autoremove feature to the backup instance Date: Wed, 7 Jan 2026 23:46:07 +0900 Message-ID: <176779716708.4193242.18165634129732047971.stgit@mhiramat.tok.corp.google.com> X-Mailer: git-send-email 2.52.0.351.gbe84eed79e-goog In-Reply-To: <176779714767.4193242.1978666866487010024.stgit@mhiramat.tok.corp.google.com> References: <176779714767.4193242.1978666866487010024.stgit@mhiramat.tok.corp.google.com> User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable From: Masami Hiramatsu (Google) Since the backup instance is readonly, after reading all data via pipe, no data is left on the instance. Thus it can be removed safely after closing all files. Signed-off-by: Masami Hiramatsu (Google) --- kernel/trace/trace.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++= +++- kernel/trace/trace.h | 6 +++++ 2 files changed, 69 insertions(+), 1 deletion(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 725930f5980e..dfd4385603e6 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -590,6 +590,55 @@ void trace_set_ring_buffer_expanded(struct trace_array= *tr) tr->ring_buffer_expanded =3D true; } =20 +static int __remove_instance(struct trace_array *tr); + +static void trace_array_autoremove(struct work_struct *work) +{ + struct trace_array *tr =3D container_of(work, struct trace_array, autorem= ove_work); + + guard(mutex)(&event_mutex); + guard(mutex)(&trace_types_lock); + + /* + * This can be fail if someone gets @tr before starting this + * function, but in that case, this will be kicked again when + * putting it. So we don't care the result. + */ + __remove_instance(tr); +} + +static struct workqueue_struct *autoremove_wq; + +static void trace_array_init_autoremove(struct trace_array *tr) +{ + INIT_WORK(&tr->autoremove_work, trace_array_autoremove); +} + +static void trace_array_kick_autoremove(struct trace_array *tr) +{ + if (!work_pending(&tr->autoremove_work) && autoremove_wq) + queue_work(autoremove_wq, &tr->autoremove_work); +} + +static void trace_array_cancel_autoremove(struct trace_array *tr) +{ + if (work_pending(&tr->autoremove_work)) + cancel_work(&tr->autoremove_work); +} + +__init static int trace_array_init_autoremove_wq(void) +{ + autoremove_wq =3D alloc_workqueue("tr_autoremove_wq", + WQ_UNBOUND | WQ_HIGHPRI, 0); + if (!autoremove_wq) { + pr_err("Unable to allocate tr_autoremove_wq\n"); + return -ENOMEM; + } + return 0; +} + +late_initcall_sync(trace_array_init_autoremove_wq); + LIST_HEAD(ftrace_trace_arrays); =20 int trace_array_get(struct trace_array *this_tr) @@ -598,7 +647,7 @@ int trace_array_get(struct trace_array *this_tr) =20 guard(mutex)(&trace_types_lock); list_for_each_entry(tr, &ftrace_trace_arrays, list) { - if (tr =3D=3D this_tr) { + if (tr =3D=3D this_tr && !tr->free_on_close) { tr->ref++; return 0; } @@ -611,6 +660,12 @@ static void __trace_array_put(struct trace_array *this= _tr) { WARN_ON(!this_tr->ref); this_tr->ref--; + /* + * When free_on_close is set, prepare removing the array + * when the last reference is released. + */ + if (this_tr->ref =3D=3D 1 && this_tr->free_on_close) + trace_array_kick_autoremove(this_tr); } =20 /** @@ -6212,6 +6267,10 @@ static void update_last_data(struct trace_array *tr) /* Only if the buffer has previous boot data clear and update it. */ tr->flags &=3D ~TRACE_ARRAY_FL_LAST_BOOT; =20 + /* If this is a backup instance, mark it for autoremove. */ + if (tr->flags & TRACE_ARRAY_FL_VMALLOC) + tr->free_on_close =3D true; + /* Reset the module list and reload them */ if (tr->scratch) { struct trace_scratch *tscratch =3D tr->scratch; @@ -10392,6 +10451,8 @@ trace_array_create_systems(const char *name, const = char *systems, if (ftrace_allocate_ftrace_ops(tr) < 0) goto out_free_tr; =20 + trace_array_init_autoremove(tr); + ftrace_init_trace_array(tr); =20 init_trace_flags_index(tr); @@ -10540,6 +10601,7 @@ static int __remove_instance(struct trace_array *tr) if (update_marker_trace(tr, 0)) synchronize_rcu(); =20 + trace_array_cancel_autoremove(tr); tracing_set_nop(tr); clear_ftrace_function_probes(tr); event_trace_del_tracer(tr); diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h index bc0eeb2d1d07..a8088a106d67 100644 --- a/kernel/trace/trace.h +++ b/kernel/trace/trace.h @@ -446,6 +446,12 @@ struct trace_array { * we do not waste memory on systems that are not using tracing. */ bool ring_buffer_expanded; + /* + * If the ring buffer is a read only backup instance, it will be + * removed after dumping all data via pipe, because no readable data. + */ + bool free_on_close; + struct work_struct autoremove_work; }; =20 enum {