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[131.252.210.177]) by mx.google.com with ESMTPS id p1si1113298pld.28.2019.08.22.19.12.33 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 22 Aug 2019 19:12:33 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of dri-devel-bounces@lists.freedesktop.org designates 131.252.210.177 as permitted sender) client-ip=131.252.210.177; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of dri-devel-bounces@lists.freedesktop.org designates 131.252.210.177 as permitted sender) smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 813706EBA6; Fri, 23 Aug 2019 02:12:31 +0000 (UTC) X-Original-To: dri-devel@lists.freedesktop.org Delivered-To: dri-devel@lists.freedesktop.org Received: from mail-oi1-f193.google.com (mail-oi1-f193.google.com [209.85.167.193]) by gabe.freedesktop.org (Postfix) with ESMTPS id ABA5D6EBA5 for ; Fri, 23 Aug 2019 02:12:26 +0000 (UTC) Received: by mail-oi1-f193.google.com with SMTP id l2so5938529oil.0 for ; Thu, 22 Aug 2019 19:12:26 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=PierwHszPjoIfoYM+aQ/lMW44n7AHzmYyHh9ldDk9CQ=; b=j6AhVDUU+lX/mtw7ztV+RZDv/8GW+r61x+U0zETNHFVPlLjzVsbMJnKvn3wHDeigFt 5g0xHM+ho64Pez28bVZ2BMdBw0G99D7m44hR+vD719YgSa4cbf5puYwg43lt5ys9hurX kHeAHCyieN07HI2HsUoGzblM7kfclnJSfk0axuqiIT0rwQa2TK6xDUINtsygVNwDkPD5 ph23RGpnUkSriq15sJsTjX0GV8Pr+iOaMADNZNVavPLt7jS0xfGQXArGnQSyOZqI8dji wFkHTW1d333GoiDVZQK3I2ZqcM61kXTdLRYGUD9AgKdHBu18KwYv3YCBUeW9P+Bw/9f6 egbA== X-Gm-Message-State: APjAAAVx6NxO0fRu82+bN8UvHuPcOXHdjtSktf5oHKh/Z3Xh3zCYCJfL NGMU0ikyL3kdx21N3nx6kJcKJSE= X-Received: by 2002:aca:61c5:: with SMTP id v188mr1576196oib.34.1566526344892; Thu, 22 Aug 2019 19:12:24 -0700 (PDT) Received: from xps15.herring.priv (24-155-109-49.dyn.grandenetworks.net. [24.155.109.49]) by smtp.googlemail.com with ESMTPSA id c1sm457747oic.31.2019.08.22.19.12.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 22 Aug 2019 19:12:24 -0700 (PDT) From: Rob Herring To: dri-devel@lists.freedesktop.org Subject: [PATCH v2 5/8] drm/shmem: Use mutex_trylock in drm_gem_shmem_purge Date: Thu, 22 Aug 2019 21:12:13 -0500 Message-Id: <20190823021216.5862-6-robh@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20190823021216.5862-1-robh@kernel.org> References: <20190823021216.5862-1-robh@kernel.org> MIME-Version: 1.0 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Maxime Ripard , Tomeu Vizoso , David Airlie , Sean Paul , Steven Price , Boris Brezillon , Alyssa Rosenzweig , Robin Murphy Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Lockdep reports a circular locking dependency with pages_lock taken in the shrinker callback. The deadlock can't actually happen with current users at least as a BO will never be purgeable when pages_lock is held. To be safe, let's use mutex_trylock() instead and bail if a BO is locked already. WARNING: possible circular locking dependency detected 5.3.0-rc1+ #100 Tainted: G L ------------------------------------------------------ kswapd0/171 is trying to acquire lock: 000000009b9823fd (&shmem->pages_lock){+.+.}, at: drm_gem_shmem_purge+0x20/0x40 but task is already holding lock: 00000000f82369b6 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x40 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (fs_reclaim){+.+.}: fs_reclaim_acquire.part.18+0x34/0x40 fs_reclaim_acquire+0x20/0x28 __kmalloc_node+0x6c/0x4c0 kvmalloc_node+0x38/0xa8 drm_gem_get_pages+0x80/0x1d0 drm_gem_shmem_get_pages+0x58/0xa0 drm_gem_shmem_get_pages_sgt+0x48/0xd0 panfrost_mmu_map+0x38/0xf8 [panfrost] panfrost_gem_open+0xc0/0xe8 [panfrost] drm_gem_handle_create_tail+0xe8/0x198 drm_gem_handle_create+0x3c/0x50 panfrost_gem_create_with_handle+0x70/0xa0 [panfrost] panfrost_ioctl_create_bo+0x48/0x80 [panfrost] drm_ioctl_kernel+0xb8/0x110 drm_ioctl+0x244/0x3f0 do_vfs_ioctl+0xbc/0x910 ksys_ioctl+0x78/0xa8 __arm64_sys_ioctl+0x1c/0x28 el0_svc_common.constprop.0+0x90/0x168 el0_svc_handler+0x28/0x78 el0_svc+0x8/0xc -> #0 (&shmem->pages_lock){+.+.}: __lock_acquire+0xa2c/0x1d70 lock_acquire+0xdc/0x228 __mutex_lock+0x8c/0x800 mutex_lock_nested+0x1c/0x28 drm_gem_shmem_purge+0x20/0x40 panfrost_gem_shrinker_scan+0xc0/0x180 [panfrost] do_shrink_slab+0x208/0x500 shrink_slab+0x10c/0x2c0 shrink_node+0x28c/0x4d8 balance_pgdat+0x2c8/0x570 kswapd+0x22c/0x638 kthread+0x128/0x130 ret_from_fork+0x10/0x18 other info that might help us debug this: Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(fs_reclaim); lock(&shmem->pages_lock); lock(fs_reclaim); lock(&shmem->pages_lock); *** DEADLOCK *** 3 locks held by kswapd0/171: #0: 00000000f82369b6 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x40 #1: 00000000ceb37808 (shrinker_rwsem){++++}, at: shrink_slab+0xbc/0x2c0 #2: 00000000f31efa81 (&pfdev->shrinker_lock){+.+.}, at: panfrost_gem_shrinker_scan+0x34/0x180 [panfrost] Fixes: 17acb9f35ed7 ("drm/shmem: Add madvise state and purge helpers") Cc: Maarten Lankhorst Cc: Maxime Ripard Cc: Sean Paul Cc: David Airlie Cc: Daniel Vetter Signed-off-by: Rob Herring Reviewed-by: Steven Price --- drivers/gpu/drm/drm_gem_shmem_helper.c | 7 +++++-- include/drm/drm_gem_shmem_helper.h | 2 +- 2 files changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/drm_gem_shmem_helper.c b/drivers/gpu/drm/drm_gem_shmem_helper.c index 5423ec56b535..f5918707672f 100644 --- a/drivers/gpu/drm/drm_gem_shmem_helper.c +++ b/drivers/gpu/drm/drm_gem_shmem_helper.c @@ -415,13 +415,16 @@ void drm_gem_shmem_purge_locked(struct drm_gem_object *obj) } EXPORT_SYMBOL(drm_gem_shmem_purge_locked); -void drm_gem_shmem_purge(struct drm_gem_object *obj) +bool drm_gem_shmem_purge(struct drm_gem_object *obj) { struct drm_gem_shmem_object *shmem = to_drm_gem_shmem_obj(obj); - mutex_lock(&shmem->pages_lock); + if (!mutex_trylock(&shmem->pages_lock)) + return false; drm_gem_shmem_purge_locked(obj); mutex_unlock(&shmem->pages_lock); + + return true; } EXPORT_SYMBOL(drm_gem_shmem_purge); diff --git a/include/drm/drm_gem_shmem_helper.h b/include/drm/drm_gem_shmem_helper.h index ce1600fdfc3e..01f514521687 100644 --- a/include/drm/drm_gem_shmem_helper.h +++ b/include/drm/drm_gem_shmem_helper.h @@ -134,7 +134,7 @@ static inline bool drm_gem_shmem_is_purgeable(struct drm_gem_shmem_object *shmem } void drm_gem_shmem_purge_locked(struct drm_gem_object *obj); -void drm_gem_shmem_purge(struct drm_gem_object *obj); +bool drm_gem_shmem_purge(struct drm_gem_object *obj); struct drm_gem_shmem_object * drm_gem_shmem_create_with_handle(struct drm_file *file_priv,