On Mon, Mar 4, 2013 at 9:19 AM, Paul Menzel <pm.debian@xxxxxxxxxxxxxx> wrote: > > Am Montag, den 04.03.2013, 08:45 -0800 schrieb Paul Taysom: > > Changed the dm-verity prefetching to use a worker thread to avoid > > a deadlock in dm-bufio. > > Do you know of any bug reports about this? Searching for »dm-verity dead > lock« I found [1], which seems to be the issue, right? If yes, please > reference it. > > > If generic_make_request is called recursively, it queues the I/O > > request on the current->bio_list without making the I/O request > > and returns. The routine making the recursive call cannot wait > > for the I/O to complete. > > > > The deadlock occurred when one thread grabbed the bufio_client > > mutex and waited for an I/O to complete but the I/O was queued > > on another thread’s current->bio_list and it was waiting to get > > the mutex held by the first thread. > > > > The fix allows only one I/O request from dm-verity to dm-bufio > > per thread. To do this, the prefetch requests were queued on worker > > threads. > > > > In addition to avoiding the deadlock, this fix made a slight > > improvement in performance. > > > > seconds_kernel_to_login: > > with prefetch: 8.43s > > without prefetch: 9.2s > > worker prefetch: 8.28s > > > > Signed-off-by: Paul Taysom <taysom@xxxxxxxxxxxx> > > --- > > drivers/md/dm-verity.c | 29 +++++++++++++++++++++++++++-- > > 1 file changed, 27 insertions(+), 2 deletions(-) > > Acked-by: Paul Menzel <paulepanter@xxxxxxxxxxxxxxxxxxxxx> > > > Thanks, > > Paul > > > [1] https://code.google.com/p/chromium-os/issues/detail?id=39148 Yes, I should have included that this fix addresses http://crosbug.com/39148 Thanks, Paul -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
