Date: Sun, 2 Aug 2020 16:34:27 +0000 (UTC) From: Conrad Meyer <cem@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r363770 - head/sys/kern Message-ID: <202008021634.072GYR5B002922@repo.freebsd.org>
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Author: cem Date: Sun Aug 2 16:34:27 2020 New Revision: 363770 URL: https://svnweb.freebsd.org/changeset/base/363770 Log: Unlocked getblk: Fix new false-positive assertion A free buf's lock may be held (temporarily) due to unlocked lookup, so buf_alloc() must acquire it without LK_NOWAIT. The unlocked getblk path should unlock it promptly once it realizes the identity does not match the buffer it was searching for. Reported by: gallatin Reviewed by: kib Tested by: pho X-MFC-With: r363482 Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D25914 Modified: head/sys/kern/vfs_bio.c Modified: head/sys/kern/vfs_bio.c ============================================================================== --- head/sys/kern/vfs_bio.c Sun Aug 2 04:25:36 2020 (r363769) +++ head/sys/kern/vfs_bio.c Sun Aug 2 16:34:27 2020 (r363770) @@ -1637,7 +1637,7 @@ static struct buf * buf_alloc(struct bufdomain *bd) { struct buf *bp; - int freebufs; + int freebufs, error; /* * We can only run out of bufs in the buf zone if the average buf @@ -1660,8 +1660,10 @@ buf_alloc(struct bufdomain *bd) if (freebufs == bd->bd_lofreebuffers) bufspace_daemon_wakeup(bd); - if (BUF_LOCK(bp, LK_EXCLUSIVE | LK_NOWAIT, NULL) != 0) - panic("getnewbuf_empty: Locked buf %p on free queue.", bp); + error = BUF_LOCK(bp, LK_EXCLUSIVE, NULL); + KASSERT(error == 0, ("%s: BUF_LOCK on free buf %p: %d.", __func__, bp, + error)); + (void)error; KASSERT(bp->b_vp == NULL, ("bp: %p still has vnode %p.", bp, bp->b_vp));
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