Roland McGrath <[email protected]> writes: > [PATCH] Disable CLONE_CHILD_CLEARTID for abnormal exit. > > The CLONE_CHILD_CLEARTID flag is used by NPTL to have its threads > communicate via memory/futex when they exit, so pthread_join can > synchronize using a simple futex wait. The word of user memory where NPTL > stores a thread's own TID is what it passes; this gets reset to zero at > thread exit. > > It is not desireable to touch this user memory when threads are dying due > to a fatal signal. A core dump is more usefully representative of the > dying program state if the threads live at the time of the crash have their > NPTL data structures unperturbed. The userland expectation of > CLONE_CHILD_CLEARTID has only ever been that it works for a thread making > an _exit system call.
This breaks nscd. It uses CLONE_CHILD_CLEARTID to clear the nscd_certainly_running flag in the shared databases, so that the clients are notified when nscd is restarted. Now, when nscd uses a non-persistent database, the clients that have it mapped keep thinking the database is being updated by nscd, when in fact nscd has created a new (anonymous) one (for non-persistent databases it uses an unlinked file as backend). Andreas. -- Andreas Schwab, SUSE Labs, [email protected] GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7 "And now for something completely different." -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
