Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751735AbbLUUlE (ORCPT ); Mon, 21 Dec 2015 15:41:04 -0500 Received: from mga11.intel.com ([192.55.52.93]:47911 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751376AbbLUUlB (ORCPT ); Mon, 21 Dec 2015 15:41:01 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.20,460,1444719600"; d="scan'208";a="846027064" Message-ID: <1450730477.30729.274.camel@linux.intel.com> Subject: Re: [PATCH] ata: sata_dwc_460ex: remove incorrect locking From: Andy Shevchenko To: Mans Rullgard , Tejun Heo , linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Julian Margetson Date: Mon, 21 Dec 2015 22:41:17 +0200 In-Reply-To: <1450721870-23266-1-git-send-email-mans@mansr.com> References: <1450721870-23266-1-git-send-email-mans@mansr.com> Organization: Intel Finland Oy Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.18.2-1 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4937 Lines: 137 On Mon, 2015-12-21 at 18:17 +0000, Mans Rullgard wrote: > 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: > +Julian. I think Julian may give his Tested-by: tag. > ============================================= > [ 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. > Clearing the PM -- Andy Shevchenko Intel Finland Oy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/