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a8c27c0bea
On systems with CONFIG_PREEMPT=n, under certain circumstances, mmcqd can continuously process requests for several seconds without blocking, triggering the soft lockup watchdog. For example, this can happen if mmcqd runs on the CPU which services the controller's interrupt, and a process on a different CPU continuously writes to the MMC block device. NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [mmcqd/0:664] CPU: 0 PID: 664 Comm: mmcqd/0 Not tainted 4.1.0-rc7+ #4 PC is at _raw_spin_unlock_irqrestore+0x24/0x28 LR is at mmc_start_request+0x104/0x134 ... [<805112a8>] (_raw_spin_unlock_irqrestore) from [<803db664>] (mmc_start_request+0x104/0x134) [<803db664>] (mmc_start_request) from [<803dc008>] (mmc_start_req+0x274/0x394) [<803dc008>] (mmc_start_req) from [<803eb2c4>] (mmc_blk_issue_rw_rq+0xd0/0xb98) [<803eb2c4>] (mmc_blk_issue_rw_rq) from [<803ebe8c>] (mmc_blk_issue_rq+0x100/0x470) [<803ebe8c>] (mmc_blk_issue_rq) from [<803ecab8>] (mmc_queue_thread+0xd0/0x170) [<803ecab8>] (mmc_queue_thread) from [<8003fd14>] (kthread+0xe0/0xfc) [<8003fd14>] (kthread) from [<8000f768>] (ret_from_fork+0x14/0x2c) Fix it by adding a cond_resched() in the request handling loop so that other processes get a chance to run. Signed-off-by: Rabin Vincent <rabin.vincent@axis.com> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org> |
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