On Thu, Jan 03, 2013 at 05:26:39PM -0500, Tejun Heo wrote: > Hello, Trond. > > On Thu, Jan 03, 2013 at 10:12:32PM +0000, Myklebust, Trond wrote: > > > The analysis is likely completely wrong, so please don't go off doing > > > something unnecessary. Please take look at what's causing the > > > deadlocks again. > > > > The analysis is a no-brainer: > > We see a deadlock due to one work item waiting for completion of another > > work item that is queued on the same CPU. There is no other dependency > > between the two work items. > > What do you mean "waiting for completion of"? Is one flushing the > other? Or is one waiting for the other to take certain action? How > are the two work items related? Are they queued on the same > workqueue? Can you create a minimal repro case of the observed > deadlock?
Ooh, BTW, there was a bug where workqueue code created a false dependency between two work items. Workqueue currently considers two work items to be the same if they're on the same address and won't execute them concurrently - ie. it makes a work item which is queued again while being executed wait for the previous execution to complete. If a work function frees the work item, and then waits for an event which should be performed by another work item and *that* work item recycles the freed work item, it can create a false dependency loop. There really is no reliable way to detect this short of verifying every memory free. A patch is queued to make such occurrences less likely (work functions should also match for two work items considered the same), but if you're seeing this, the best thing to do is freeing the work item at the end of the work function. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
