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Tue, 13 Nov 2018 16:28:54 -0800 (PST) Cc: rafael.tinoco@linaro.org, Waiman Long Subject: Re: nfs: possible sync issue between nfs_call_unlink <-> nfs_async_unlink_release To: linux-kernel@vger.kernel.org References: From: Rafael David Tinoco Organization: Linaro Message-ID: Date: Tue, 13 Nov 2018 22:28:52 -0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/3/18 6:04 PM, Rafael Tinoco wrote: > BUG: https://bugs.linaro.org/show_bug.cgi?id=3731 > > During Linaro's Kernel Functional tests, we have observed the > following situation: > > [ 52.651490] DEBUG_LOCKS_WARN_ON(sem->owner != ((struct task_struct *)1UL)) > [ 52.651506] WARNING: CPU: 2 PID: 1457 at > ./kernel/locking/rwsem.c:217 up_read_non_owner+0x5d/0x70 > [ 52.674398] Modules linked in: x86_pkg_temp_thermal fuse > [ 52.679719] CPU: 2 PID: 1457 Comm: kworker/2:2 Not tainted 4.16.0 #1 > [ 52.687448] Hardware name: Supermicro SYS-5019S-ML/X11SSH-F, BIOS > 2.0b 07/27/2017 > [ 52.694922] Workqueue: nfsiod rpc_async_release > [ 52.699454] RIP: 0010:up_read_non_owner+0x5d/0x70 > [ 52.704157] RSP: 0018:ffff9cbf81a23dd0 EFLAGS: 00010282 > [ 52.709376] RAX: 0000000000000000 RBX: ffff8dc1983c76c0 RCX: 0000000000000000 > [ 52.716500] RDX: ffffffffbd2d26c9 RSI: 0000000000000001 RDI: ffffffffbd2d2889 > [ 52.723652] RBP: ffff9cbf81a23dd8 R08: 0000000000000000 R09: 0000000000000000 > [ 52.730782] R10: ffff9cbf81a23dd0 R11: 0000000000000000 R12: ffff8dc19abf8600 > [ 52.737906] R13: ffff8dc19b6c0000 R14: 0000000000000000 R15: ffff8dc19bacad80 > [ 52.745029] FS: 0000000000000000(0000) GS:ffff8dc1afd00000(0000) > knlGS:0000000000000000 > [ 52.753108] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 52.758845] CR2: 00007f33794665d8 CR3: 000000016c41e006 CR4: 00000000003606e0 > [ 52.765968] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > [ 52.773091] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 > [ 52.780215] Call Trace: > [ 52.782695] nfs_async_unlink_release+0x32/0x80 > [ 52.787220] rpc_free_task+0x30/0x50 > [ 52.790789] rpc_async_release+0x12/0x20 > [ 52.794707] process_one_work+0x25e/0x660 > [ 52.798713] worker_thread+0x4b/0x410 > [ 52.802377] kthread+0x10d/0x140 > [ 52.805600] ? rescuer_thread+0x3a0/0x3a0 > [ 52.809652] ? kthread_create_worker_on_cpu+0x70/0x70 > [ 52.814702] ? do_syscall_64+0x69/0x1b0 > [ 52.818540] ret_from_fork+0x3a/0x50 Full explanation: https://bugs.linaro.org/show_bug.cgi?id=3731#c15 Appears that: commit 925b9cd1b89a94b7124d128c80dfc48f78a63098 Author: Waiman Long Date: Thu Sep 6 17:18:34 2018 locking/rwsem: Make owner store task pointer of last owning reader seem to have fixed this warning: DEBUG_RWSEMS_WARN_ON() started differentiating unknown owners for semaphores, like in this case, when RPC function forces the release the dentry's semaphore to avoid issues with NFS filesystem logic (nfs_rmdir, the real user for the semaphore in question). Thanks Waiman! - Rafael D. Tinoco Linaro Kernel Validation