Date: Sun, 11 Jun 2006 16:41:18 -0400 From: Kris Kennaway <kris@obsecurity.org> To: current@FreeBSD.org, smp@FreeBSD.org Cc: alfred@FreeBSD.org Subject: Optional MPSAFE syscalls aren't Message-ID: <20060611204118.GA34272@xor.obsecurity.org>
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--8t9RHnE3ZwKMSgU+ Content-Type: text/plain; charset=us-ascii Content-Disposition: inline rwatson, pjd and I tracked down the following problem when looking at postgresql profiling traces: For syscalls that are part of subsystems that may be loaded from kld, the SYSCALL_MODULE_HELPER() spams the copy of the sysent from syscalls.master - and it never sets the SYF_MPSAFE flag. This means that regardless of what syscalls.master says about mpsafety, such syscalls always acquire Giant. One sad consequence of this is that when I removed the SYSCALL_MODULE_HELPERs from sysv_sem.c to get rid of the bogus Giant locking that seems to be hurting performance, postgresql hangs when trying to start; possibly the locking in sysv_sem.c is just broken since it was always implicitly serialized by Giant, so never in fact tested at all. Apart from the SYSV IPC syscalls, this also affects the AIO and mqueue code. Kris --8t9RHnE3ZwKMSgU+ Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.3 (FreeBSD) iD8DBQFEjH/tWry0BWjoQKURAnOBAJwIjkCtdgOX2xYvSICPMIvRmNyixwCfQVKo 05fj0qqtGsccpp9SO+w07yg= =PPG4 -----END PGP SIGNATURE----- --8t9RHnE3ZwKMSgU+--
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