From mboxrd@z Thu Jan  1 00:00:00 1970
From: buyit@live.cn (buyitian)
Date: Fri, 15 Feb 2013 16:52:21 +0800
Subject: spinlock deadlock
Message-ID: <BLU002-W25EB17366DDB90B28445F6BC0E0@phx.gbl>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

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. 

 		 	   		  
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