On Fri, 15 Feb 2013 17:17:38 +0530, anish singh said: > adding Joe Perches as generally he looks after printk stuff. > > On Fri, Feb 15, 2013 at 2:22 PM, buyitian <buyit@xxxxxxx> wrote: > > is it possible that printk cause deadlock? the path is as below: > > > > 1. taskA runs on CPU0, and run schedule to acqire the rq->lock. > > 2. taskA calls printk while holding rq->lock. > > 3. taskA holds console_sem. > > 4. taskB runs on CPU1, and call console_lock(), which is blocked by > > console_sem and queue itslef to the wait list. > > 5. taskB migrates from CPU1 to cpu0. will this step occur? > > 6. taskA calls up(&console_sem)--> > > wake_up_process()-->try_to_wake_up()-->ttwu_queue()-->raw_spin_lock(&rq->lock). > > here taskA tries to acquire the rq->lock of CPU0 again. I'm not Joe, but what kernel release are you looking at? ISTR that in the last few releases (3.5-ish maybe?), that code got overhauled to prevent a similar issue...
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