Hello, Peter. On Fri, Aug 07, 2015 at 05:59:54PM +0200, Peter Zijlstra wrote: > > So, the problem there is that __kthread_bind() doesn't grab the same > > lock that the syscall side grabs but workqueue used > > set_cpus_allowed_ptr() which goes through the rq locking, so as long > > as the check on syscall side is movied inside rq lock, it should be > > fine. > > Currently neither site uses any lock, and that is what the patch fixes > (it uses the per-task ->pi_lock instead of the rq->lock, but that is > immaterial).
Yeap, the testing on the syscall side should definitely be moved inside rq->lock. > What matters though is that you now must hold a scheduler lock while > setting PF_NO_SETAFFINITY. In order to avoid spreading that knowledge > around I've taught kthread_bind*() about this and made the workqueue > code use that API (rather than having the workqueue code take scheduler > locks). So, as long as PF_NO_SETAFFINITY is set before the task sets its affinity to its target holding the rq lock, it should still be safe. > Hmm.. a better solution. Have the worker thread creation call > kthread_bind_mask() before attach_to_pool() and have attach_to_pool() > keep using set_cpus_allowed_ptr(). Less ugly. Yeah, that works too. About the same effect. 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/
