On Wed, Feb 12, 2014 at 05:10:38PM +1100, Dave Chinner wrote: > On Wed, Feb 12, 2014 at 12:50:27AM -0500, Dave Jones wrote: > > On Wed, Feb 12, 2014 at 04:40:43PM +1100, Dave Chinner wrote: > > > > > None of the XFS code disables interrupts in that path, not does is > > > call outside XFS except to dispatch IO. The stack is pretty deep at > > > this point and I know that the standard (non stacked) IO stack can > > > consume >3kb of stack space when it gets down to having to do memory > > > reclaim during GFP_NOIO allocation at the lowest level of SCSI > > > drivers. Stack overruns typically show up with symptoms like we are > > > seeing. > > > .. > > > > > > Dave, before chasing ghosts, can you (like Eric originally asked) > > > turn on stack overrun detection? > > > > CONFIG_DEBUG_STACKOVERFLOW ? Already turned on. > > That only checks stack usage when an interrupt is taken. If no > interrupts are taken when stack usage is within 128 bytes of > overflow, then it doesn't catch it. > > I tend to use CONFIG_DEBUG_STACK_USAGE=y as it records the maximum > stack usage of a process via canary overwrites and it records it in > do_exit(). I also use the stack tracer to record the largest stack > usage seen so I know exactly what code paths are approaching stack > overruns...
FYI, just creating lots of files with open(O_CREAT): [ 348.718357] fs_mark (4828) used greatest stack depth: 2968 bytes left [ 348.769846] fs_mark (4814) used greatest stack depth: 2312 bytes left [ 349.777717] fs_mark (4826) used greatest stack depth: 2280 bytes left [ 418.139415] fs_mark (4928) used greatest stack depth: 1936 bytes left [ 460.492282] fs_mark (4993) used greatest stack depth: 1336 bytes left [ 544.825418] fs_mark (5104) used greatest stack depth: 1112 bytes left [ 689.503970] fs_mark (5265) used greatest stack depth: 1000 bytes left We've got absolutely no spare stack space anymore in the IO path. And the IO path can't get much simpler than filesystem -> virtio block device. Cheers, Dave. -- Dave Chinner da...@fromorbit.com -- 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/
