https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=225960
--- Comment #5 from Andriy Gapon <[email protected]> --- I now think that this could be a / the deep problem in GEOM. The problem is that g_access() must be called with the GEOM topology lock held. And that gives a false impression that the lock is indeed held across the call. But this isn't true because many classes, ZVOL being one of the many, need to perform I/O in their access method. So, they must drop and pick up the topology lock. That, of course, can break many assumptions. Specifically, looking at g_slice_access() we can see that the code assumes that all invocations are serialized. Indeed, if another call to g_slice_access() is permitted while the consumer's access bits are not updated yet, then the following condition can be true multiple times: /* On first open, grab an extra "exclusive" bit */ if (cp->acr == 0 && cp->acw == 0 && cp->ace == 0) de++; And if that ever happens and we have extra grabs on cp->ace, then the following condition will never be true (because cp->ace + de > 1): /* ... and let go of it on last close */ if ((cp->acr + dr) == 0 && (cp->acw + dw) == 0 && (cp->ace + de) == 1) de--; -- You are receiving this mail because: You are the assignee for the bug. _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-bugs To unsubscribe, send any mail to "[email protected]"
