On Wed, Aug 31, 2011 at 2:17 PM, Daniel Baluta <[email protected]>wrote:
> Hello, > > i wrote a linux kernel module which uses mmap_sem in lots of places. I > grab > > mmap_sem for both reads & writes. And, i also use page_table_lock > spinlock > > under them. The problem i have is that there is a hard to reproduce a > race > > condition bug in which a thread doesn't release the semaphore at all. > Hence, > > ps hangs as ps needs to grab mmap_sem for the processes. The question is > how > > do i find the thread that is holding the semaphore forever. It will help > me > > figure out the part of the code the race is in. > > So, the question is : I have some number of threads grabbing the > semaphore > > for read/write. One of them grabs it & doesn't release at all. How do i > find > > the thread that is holding it. This is not a soft lockup & i dont get any > > hung_task_timeout messages. > > Any help is appreciated. > > You could turn on lockdep (LOCKDEP_SUPPORT=y), > and see if any warnings are triggered. > LOCKDEP_SUPPORT is turned on in my kernel but I dont see any warnings. Thanks though. Venkatram > > thanks, > Daniel. >
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