Gregory Haskins wrote: > *Patch submitted for inclusion in PREEMPT_RT 26-rt4. Applies to 2.6.26.3-rt3* > > Hi Ingo, Steven, Thomas, > Please consider for -rt4. This fixes a nasty deadlock on my systems under > heavy load. > > [ > Changelog: > v2: only touch seqlock_t because raw_seqlock_t doesn't require > serialization and userspace cannot modify data during a read > > v1: initial release > ] > Hi Andi, As it turns out, my distcc backend was an x86_64 machine running the v1 patch and I started to notice sometime today that certain cc1 jobs were sometimes (albeit rarely) segfaulting on me. I noticed that before I even published the first patch, but I chalked it up to a corrupt .o on my NFS home. Plus I was forgetting that the distcc machine was running the patch, and I would probably have never made the userspace connection had you not mentioned it. In any case, I self-built this v2 patch with v2 applied, and the segfaults have gone away. So I think we know several things: 1) You were right that this would cause an issue if the slow path is hit. 2) Steven was right that userspace must use raw_seqlock_t because it no longer crashes with v2. 3) I am satisfied that my primary concern is still properly addressed. Hopefully everyone is satisfied with this patch now. Thanks for the help. It's much appreciated! -Greg
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