Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751451AbbLUSSE (ORCPT ); Mon, 21 Dec 2015 13:18:04 -0500 Received: from unicorn.mansr.com ([81.2.72.234]:54324 "EHLO unicorn.mansr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751142AbbLUSSA (ORCPT ); Mon, 21 Dec 2015 13:18:00 -0500 From: Mans Rullgard To: Tejun Heo , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Andy Shevchenko Subject: [PATCH] ata: sata_dwc_460ex: remove incorrect locking Date: Mon, 21 Dec 2015 18:17:50 +0000 Message-Id: <1450721870-23266-1-git-send-email-mans@mansr.com> X-Mailer: git-send-email 2.6.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4424 Lines: 112 This lock is already taken in ata_scsi_queuecmd() a few levels up the call stack so attempting to take it here is an error. Moreover, it is pointless in the first place since it only protects a single, atomic assignment. Enabling lock debugging gives the following output: ============================================= [ INFO: possible recursive locking detected ] 4.4.0-rc5+ #189 Not tainted --------------------------------------------- kworker/u2:3/37 is trying to acquire lock: (&(&host->lock)->rlock){-.-...}, at: [<90283294>] sata_dwc_exec_command_by_tag.constprop.14+0x44/0x8c but task is already holding lock: (&(&host->lock)->rlock){-.-...}, at: [<902761ac>] ata_scsi_queuecmd+0x2c/0x330 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(&host->lock)->rlock); lock(&(&host->lock)->rlock); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by kworker/u2:3/37: #0: ("events_unbound"){.+.+.+}, at: [<9003a0a4>] process_one_work+0x12c/0x430 #1: ((&entry->work)){+.+.+.}, at: [<9003a0a4>] process_one_work+0x12c/0x430 #2: (&bdev->bd_mutex){+.+.+.}, at: [<9011fd54>] __blkdev_get+0x50/0x380 #3: (&(&host->lock)->rlock){-.-...}, at: [<902761ac>] ata_scsi_queuecmd+0x2c/0x330 stack backtrace: CPU: 0 PID: 37 Comm: kworker/u2:3 Not tainted 4.4.0-rc5+ #189 Workqueue: events_unbound async_run_entry_fn Stack : 90b38e30 00000021 00000003 9b2a6040 00000000 9005f3f0 904fc8dc 00000025 906b96e4 00000000 90528648 9b3336c4 904fc8dc 9009bf18 00000002 00000004 00000000 00000000 9b3336c4 9b3336e4 904fc8dc 9003d074 00000000 90500000 9005e738 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6e657665 755f7374 756f626e 0000646e 00000000 00000000 9b00ca00 9b025000 ... Call Trace: [<90009d6c>] show_stack+0x88/0xa4 [<90057744>] __lock_acquire+0x1ce8/0x2154 [<900583e4>] lock_acquire+0x64/0x8c [<9045ff10>] _raw_spin_lock_irqsave+0x54/0x78 [<90283294>] sata_dwc_exec_command_by_tag.constprop.14+0x44/0x8c [<90283484>] sata_dwc_qc_issue+0x1a8/0x24c [<9026b39c>] ata_qc_issue+0x1f0/0x410 [<90273c6c>] ata_scsi_translate+0xb4/0x200 [<90276234>] ata_scsi_queuecmd+0xb4/0x330 [<9025800c>] scsi_dispatch_cmd+0xd0/0x128 [<90259934>] scsi_request_fn+0x58c/0x638 [<901a3e50>] __blk_run_queue+0x40/0x5c [<901a83d4>] blk_queue_bio+0x27c/0x28c [<901a5914>] generic_make_request+0xf0/0x188 [<901a5a54>] submit_bio+0xa8/0x194 [<9011adcc>] submit_bh_wbc.isra.23+0x15c/0x17c [<9011c908>] block_read_full_page+0x3e4/0x428 [<9009e2e0>] do_read_cache_page+0xac/0x210 [<9009fd90>] read_cache_page+0x18/0x24 [<901bbd18>] read_dev_sector+0x38/0xb0 [<901bd174>] msdos_partition+0xb4/0x5c0 [<901bcb8c>] check_partition+0x140/0x274 [<901bba60>] rescan_partitions+0xa0/0x2b0 [<9011ff68>] __blkdev_get+0x264/0x380 [<901201ac>] blkdev_get+0x128/0x36c [<901b9378>] add_disk+0x3c0/0x4bc [<90268268>] sd_probe_async+0x100/0x224 [<90043a44>] async_run_entry_fn+0x50/0x124 [<9003a11c>] process_one_work+0x1a4/0x430 [<9003a4f4>] worker_thread+0x14c/0x4fc [<900408f4>] kthread+0xd0/0xe8 [<90004338>] ret_from_kernel_thread+0x14/0x1c Fixes: 62936009f35a ("[libata] Add 460EX on-chip SATA driver, sata_dwc_460ex") Signed-off-by: Mans Rullgard --- drivers/ata/sata_dwc_460ex.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/drivers/ata/sata_dwc_460ex.c b/drivers/ata/sata_dwc_460ex.c index 902034991517..7a7faca0ddcd 100644 --- a/drivers/ata/sata_dwc_460ex.c +++ b/drivers/ata/sata_dwc_460ex.c @@ -924,15 +924,13 @@ static void sata_dwc_exec_command_by_tag(struct ata_port *ap, struct ata_taskfile *tf, u8 tag, u32 cmd_issued) { - unsigned long flags; struct sata_dwc_device_port *hsdevp = HSDEVP_FROM_AP(ap); dev_dbg(ap->dev, "%s cmd(0x%02x): %s tag=%d\n", __func__, tf->command, ata_get_cmd_descript(tf->command), tag); - spin_lock_irqsave(&ap->host->lock, flags); hsdevp->cmd_issued[tag] = cmd_issued; - spin_unlock_irqrestore(&ap->host->lock, flags); + /* * Clear SError before executing a new command. * sata_dwc_scr_write and read can not be used here. 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