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@live.cn> 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...