From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) (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 ED463243378 for ; Mon, 10 Feb 2025 13:08:57 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.251.105.195 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739192940; cv=none; b=RaecZmJpbdfd/dNkRiq4IJ1UbzHkmbBWbD5AA10mMzZxkGqQkdMZPFCt8X03akWD0fUR6eKy+zlLSj6QUHTfUR9Jg2NLZn+ZEP/yij21ow6+pbchVgoeq7kaO6/b0rps7TgpXnFMX5ICJ1tD5+LuWHqMr9hvSS7YVQ2fwibMRXM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739192940; c=relaxed/simple; bh=MfQty2qrQTi8a54QC8J/NxJbBWw8bzpg0pVBDnJN5eM=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=pw/j/wAR3A5K9EM3x1hLfDAadHtIciUg4dG4kRDCZx5zjPWx1/lWuuSMqCGnpu5tpGJZZaPCsKrIc3dsU9pPRIY3gCE3MQ0iWu+DkCnSJmCzJQ70Ioh6DURL2nRr6PapIAJGxgr6Qnx1FR2/wLLtk7cKEv5ChQbq+B4A6hw0gI4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=nZ3bRND1; arc=none smtp.client-ip=148.251.105.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="nZ3bRND1" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1739192935; bh=MfQty2qrQTi8a54QC8J/NxJbBWw8bzpg0pVBDnJN5eM=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=nZ3bRND1I4+3/opv27tOoYFzJ/VoXv8B+J1p3TITK51fcAdH3IconFNtyHIbpE7jG mgoiMD5oV1ElaudEze7939XauKfbkvDMEJNiJ1zgTY1s6czlu8Pdkl+38mBI7PT+V/ 7nsiPn+dUKKDpaYsWeOGS5IacK1RyUr60a9hwvVNPOLLvUNxUL8fWnkjdORKswFa1U JoAe+PmTIEjCwAZCVud2TFMnmu7cipdqL337Do0lTl9pq65itzjZgcXB5lPutn4ikW ZoOQ3csYPCMthYcg1Uy4ALv8z8t8U9GOfrvkjyaqhvuu9LW+xeezLcI6/0gLy6tVvh 5k6WGzoZnRvVA== Received: from localhost (unknown [IPv6:2a01:e0a:2c:6930:5cf4:84a1:2763:fe0d]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by bali.collaboradmins.com (Postfix) with ESMTPSA id 7873917E014F; Mon, 10 Feb 2025 14:08:54 +0100 (CET) Date: Mon, 10 Feb 2025 14:08:49 +0100 From: Boris Brezillon To: =?UTF-8?B?QWRyacOhbg==?= Larumbe Cc: Steven Price , Liviu Dudau , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , kernel@collabora.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] drm/panthor: Replace sleep locks with spinlocks in fdinfo path Message-ID: <20250210140849.77232318@collabora.com> In-Reply-To: <20250210124203.124191-1-adrian.larumbe@collabora.com> References: <20250210124203.124191-1-adrian.larumbe@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.3.0 (GTK 3.24.43; x86_64-redhat-linux-gnu) 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 On Mon, 10 Feb 2025 12:41:59 +0000 Adri=C3=A1n Larumbe wrote: > Panthor's fdinfo handler is routed through the /proc file system, which > executes in an atomic context. That means we cannot use mutexes because > they might sleep. >=20 > This bug was uncovered by enabling some of the kernel's mutex-debugging > features: >=20 > CONFIG_DEBUG_RT_MUTEXES=3Dy > CONFIG_DEBUG_MUTEXES=3Dy >=20 > Replace Panthor's group fdinfo data mutex with a guarded spinlock. >=20 > Signed-off-by: Adri=C3=A1n Larumbe > Fixes: e16635d88fa0 ("drm/panthor: add DRM fdinfo support") Reviewed-by: Boris Brezillon > --- > drivers/gpu/drm/panthor/panthor_sched.c | 26 ++++++++++++------------- > 1 file changed, 12 insertions(+), 14 deletions(-) >=20 > diff --git a/drivers/gpu/drm/panthor/panthor_sched.c b/drivers/gpu/drm/pa= nthor/panthor_sched.c > index 0b93bf83a9b2..7a267d1efeb6 100644 > --- a/drivers/gpu/drm/panthor/panthor_sched.c > +++ b/drivers/gpu/drm/panthor/panthor_sched.c > @@ -9,6 +9,7 @@ > #include > =20 > #include > +#include > #include > #include > #include > @@ -631,10 +632,10 @@ struct panthor_group { > struct panthor_gpu_usage data; > =20 > /** > - * @lock: Mutex to govern concurrent access from drm file's fdinfo cal= lback > - * and job post-completion processing function > + * @fdinfo.lock: Spinlock to govern concurrent access from drm file's = fdinfo > + * callback and job post-completion processing function > */ > - struct mutex lock; > + spinlock_t lock; > =20 > /** @fdinfo.kbo_sizes: Aggregate size of private kernel BO's held by t= he group. */ > size_t kbo_sizes; > @@ -910,8 +911,6 @@ static void group_release_work(struct work_struct *wo= rk) > release_work); > u32 i; > =20 > - mutex_destroy(&group->fdinfo.lock); > - > for (i =3D 0; i < group->queue_count; i++) > group_free_queue(group, group->queues[i]); > =20 > @@ -2861,12 +2860,12 @@ static void update_fdinfo_stats(struct panthor_jo= b *job) > struct panthor_job_profiling_data *slots =3D queue->profiling.slots->km= ap; > struct panthor_job_profiling_data *data =3D &slots[job->profiling.slot]; > =20 > - mutex_lock(&group->fdinfo.lock); > - if (job->profiling.mask & PANTHOR_DEVICE_PROFILING_CYCLES) > - fdinfo->cycles +=3D data->cycles.after - data->cycles.before; > - if (job->profiling.mask & PANTHOR_DEVICE_PROFILING_TIMESTAMP) > - fdinfo->time +=3D data->time.after - data->time.before; > - mutex_unlock(&group->fdinfo.lock); > + scoped_guard(spinlock, &group->fdinfo.lock) { > + if (job->profiling.mask & PANTHOR_DEVICE_PROFILING_CYCLES) > + fdinfo->cycles +=3D data->cycles.after - data->cycles.before; > + if (job->profiling.mask & PANTHOR_DEVICE_PROFILING_TIMESTAMP) > + fdinfo->time +=3D data->time.after - data->time.before; > + } > } > =20 > void panthor_fdinfo_gather_group_samples(struct panthor_file *pfile) > @@ -2880,12 +2879,11 @@ void panthor_fdinfo_gather_group_samples(struct p= anthor_file *pfile) > =20 > xa_lock(&gpool->xa); > xa_for_each(&gpool->xa, i, group) { > - mutex_lock(&group->fdinfo.lock); > + guard(spinlock)(&group->fdinfo.lock); > pfile->stats.cycles +=3D group->fdinfo.data.cycles; > pfile->stats.time +=3D group->fdinfo.data.time; > group->fdinfo.data.cycles =3D 0; > group->fdinfo.data.time =3D 0; > - mutex_unlock(&group->fdinfo.lock); > } > xa_unlock(&gpool->xa); > } > @@ -3531,7 +3529,7 @@ int panthor_group_create(struct panthor_file *pfile, > mutex_unlock(&sched->reset.lock); > =20 > add_group_kbo_sizes(group->ptdev, group); > - mutex_init(&group->fdinfo.lock); > + spin_lock_init(&group->fdinfo.lock); > =20 > return gid; > =20 >=20 > base-commit: 2eca617f12586abff62038db1c14cb3aa60a15aa > prerequisite-patch-id: 7e787ce5973b5fc7e9f69f26aa4d7e5ec03d5caa > prerequisite-patch-id: 03a619b8c741444b28435850e23d9ec463171c13 > prerequisite-patch-id: 290e1053f8bf4a8b80fb037a87cae7e096b5aa96 > prerequisite-patch-id: bc49bb8c29905650fb4788acc528bb44013c0240 > prerequisite-patch-id: 46cab4c980824c03e5164afc43085fec23e1cba5