Date: Wed, 6 Feb 2008 00:37:15 +0000 (UTC) From: Attilio Rao <attilio@FreeBSD.org> To: src-committers@FreeBSD.org, cvs-src@FreeBSD.org, cvs-all@FreeBSD.org Subject: cvs commit: src/sys/kern kern_lock.c src/sys/sys lockmgr.h Message-ID: <200802060037.m160bFNJ030997@repoman.freebsd.org>
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attilio 2008-02-06 00:37:14 UTC FreeBSD src repository Modified files: sys/kern kern_lock.c sys/sys lockmgr.h Log: Add WITNESS support to lockmgr locking primitive. This support tries to be as parallel as possible with other locking primitives, but there are differences; more specifically: - The base witness support is alredy equipped for allowing lock duplication acquisition as lockmgr rely on this. - In the case of lockmgr_disown() the lock result unlocked by witness even if it is still held by the "kernel context" - In the case of upgrading we can have 3 different situations: * Total unlocking of the shared lock and nothing else * Real witness upgrade if the owner is the first upgrader * Shared unlocking and exclusive locking if the owner is not the first upgrade but it is still allowed to upgrade - LK_DRAIN is basically handled like an exclusive acquisition Additively new options LK_NODUP and LK_NOWITNESS can now be used with lockinit(): LK_NOWITNESS disables WITNESS for the specified lock while LK_NODUP enable duplicated locks tracking. This will require manpages update and a __FreeBSD_version bumping (addressed by further commits). This patch also fixes a problem occurring if a lockmgr is held in exclusive mode and the same owner try to acquire it in shared mode: currently there is a spourious shared locking acquisition while what we really want is a lock downgrade. Probabilly, this situation can be better served with a EDEADLK failing errno return. Side note: first testing on this patch alredy reveleated several LORs reported, so please expect LORs cascades until resolved. NTFS also is reported broken by WITNESS introduction. BTW, NTFS is exposing a lock leak which needs to be fixed, and this patch can help it out if rightly tweaked. Tested by: kris, yar, Scot Hetzel <swhetzel at gmail dot com> Revision Changes Path 1.121 +46 -11 src/sys/kern/kern_lock.c 1.59 +5 -1 src/sys/sys/lockmgr.h
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