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Tue, 7 Nov 2023 08:18:09 +0000 (GMT) From: =?ks_c_5601-1987?b?sK29xcf8?= To: , , , , , , , , , , Subject: [PATCH] ALSA: core: Replace mutex_lock with mutex_trylock Date: Tue, 7 Nov 2023 17:17:59 +0900 Message-ID: <664457955.21699345385931.JavaMail.epsvc@epcpadp4> MIME-Version: 1.0 X-Mailer: Microsoft Outlook 16.0 Thread-Index: AdoRUYAmTaFEU0JCSqqAucOD379Z/w== Content-Language: ko X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFvrFLMWRmVeSWpSXmKPExsWy7bCSnO6hT56pBme2slhcuXiIyWLqwyds Fi8PaVpc+nSe3eLV4V2MFt+udDBZ/Pr/jMni6MXFTBYNd5vZLSbefc1u8XLzGyYHbo8Nn5vY PHbOusvusWlVJ5vHvJOBHt/OTGTx6NuyitFj8+nqAPYoLpuU1JzMstQifbsErozXK78zFmwU qDi2fD1zA+MD7i5GTg4JAROJj7dWMYLYQgK7GSXefBaEiEtIfNv5lQXCFpa433KEFaLmGaPE 9/0JIDabgJXE3aYpbF2MXBwiAvuYJP7PnswEkhAWcJK40nIDzGYRUJE4vOEF2CBeAUuJTUfm sEPYghInZz4BizMDHdF4uBvKlpfY/nYOM8RiBYmfT5eBLRYR0JP49KCbEaJGRGJ2ZxvzBEaB WUhGzUIyahaSUbOQtCxgZFnFKJlaUJybnltsWGCUl1quV5yYW1yal66XnJ+7iREcPVpaOxj3 rPqgd4iRiYPxEKMEB7OSCO9fe49UId6UxMqq1KL8+KLSnNTiQ4zSHCxK4rzfXvemCAmkJ5ak ZqemFqQWwWSZODilGpgs9iXdEZL4vsDA7kEaB5fH2lqm0o28PzW+zbpx6+YxNf05LaVr157T ejjjZ+JPFT3Jp7pfDPWfnppu+XfzsfsXLTa4roquPPw+aOY+pv21BwsEZge3L1JiPGMmYlC4 4qHFz6wqA9Y7W9N3zFvrxKm2zttMZwVLpnajYkXW44AnlrOCl/ZODJgqdNZ006oVcSaNmac2 vJ3IOVHj3tJ1uYs5jq58fz3g5euu6H2qBvFz9mjNYd/+x94u33jCFdGq/2l7ns5/ay/c+3Hj 46Y1ky1Pzz+14c3u1O2MjjftDmycEHGiny/nqErMdZFrK+pnOHxZlFBTaBuy7MqTrT6rL8yy lfKO2xj39bPWySv5Fj/9a5VYijMSDbWYi4oTAUuMYlINAwAA X-CMS-MailID: 20231107081810epcas2p27a897426580fce6f0884cffb256b2aaf X-Msg-Generator: CA X-Sendblock-Type: AUTO_CONFIDENTIAL CMS-TYPE: 102P X-CPGSPASS: Y X-Hop-Count: 3 X-CMS-RootMailID: 20231107081810epcas2p27a897426580fce6f0884cffb256b2aaf References: Message-ID-Hash: PBYDC636D2T4XDSBAY4ZVUTAZRFJVTTT X-Message-ID-Hash: PBYDC636D2T4XDSBAY4ZVUTAZRFJVTTT X-MailFrom: s47.kang@samsung.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-alsa-devel.alsa-project.org-0; header-match-alsa-devel.alsa-project.org-1; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.8 Precedence: list List-Id: "Alsa-devel mailing list for ALSA developers - http://www.alsa-project.org" Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Task1 waits for mutex_lock, and task2 waits for pde to be unused.(deadlock) /*call trace*/ task1 Call trace: __switch_to+0x174/0x338 schedule+0x7c/0xe8 schedule_preempt_disabled+0x24/0x40 mutex_lock+0x40/0xec snd_info_text_entry_open+0x28/0x120 proc_reg_open+0xe4/0x248 do_dentry_open+0x2a4/0x4e0 task2 Call trace: schedule_timeout+0x44/0x1c8 wait_for_completion+0x18/0x24 proc_entry_rundown+0x60/0xf0 remove_proc_subtree+0x180/0x218 proc_remove+0x20/0x30 snd_info_disconnect+0x4c/0x68 snd_info_card_disconnect+0x3c/0x58 snd_card_disconnect+0x130/0x264 usb_audio_disconnect+0xc0/0x24c /*the sequence*/ task1: - proc_reg_open: set the use_pde task2: - usb_audio_disconnect: usb device disconnection occurs - snd_info_card_disconnect: acquire the mutex_lock(&info_mutex) - proc_entry_rundown: wait_for_completion(unuse_pde) task1: - wait for mutex_lock in snd_info_text_entry_open To avoid it, a mutex without wating(mutex_trylock) shoud be used in snd_info_text_entry_open(task1). Then, when mutex_lock acquisition fails, an error is returned, and the pde becomes unused, and the mutex_lock held by task2 is released. Signed-off-by: Shinhyung Kang goto unlock; diff --git a/sound/core/info.c b/sound/core/info.c index 0b2f04dcb589..6cb4064b292e 100644 --- a/sound/core/info.c +++ b/sound/core/info.c @@ -369,7 +369,10 @@ static int snd_info_text_entry_open(struct inode *inode, struct file *file) struct snd_info_private_data *data; int err; - mutex_lock(&info_mutex); + if (!mutex_trylock(&info_mutex)) { + pr_err("%s: failed to acquire the info_mutex\n", __func__); + return -EAGAIN; + } err = alloc_info_private(entry, &data); if (err < 0)