Date: Fri, 16 Aug 2019 15:31:46 +0000 (UTC) From: Mark Johnston <markj@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r351126 - stable/12/sys/kern Message-ID: <201908161531.x7GFVkmg034143@repo.freebsd.org>
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Author: markj Date: Fri Aug 16 15:31:46 2019 New Revision: 351126 URL: https://svnweb.freebsd.org/changeset/base/351126 Log: MFC r350450, r350540: Enable witness(4) blessings. Modified: stable/12/sys/kern/subr_witness.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/kern/subr_witness.c ============================================================================== --- stable/12/sys/kern/subr_witness.c Fri Aug 16 15:25:53 2019 (r351125) +++ stable/12/sys/kern/subr_witness.c Fri Aug 16 15:31:46 2019 (r351126) @@ -132,9 +132,6 @@ __FBSDID("$FreeBSD$"); #define LI_EXCLUSIVE 0x00010000 /* Exclusive lock instance. */ #define LI_NORELEASE 0x00020000 /* Lock not allowed to be released. */ -/* Define this to check for blessed mutexes */ -#undef BLESSING - #ifndef WITNESS_COUNT #define WITNESS_COUNT 1536 #endif @@ -278,12 +275,10 @@ struct witness_lock_order_hash { u_int wloh_count; }; -#ifdef BLESSING struct witness_blessed { const char *b_lock1; const char *b_lock2; }; -#endif struct witness_pendhelp { const char *wh_type; @@ -318,9 +313,7 @@ witness_lock_order_key_equal(const struct witness_lock static int _isitmyx(struct witness *w1, struct witness *w2, int rmask, const char *fname); static void adopt(struct witness *parent, struct witness *child); -#ifdef BLESSING static int blessed(struct witness *, struct witness *); -#endif static void depart(struct witness *w); static struct witness *enroll(const char *description, struct lock_class *lock_class); @@ -727,14 +720,25 @@ static struct witness_order_list_entry order_lists[] = { NULL, NULL } }; -#ifdef BLESSING /* - * Pairs of locks which have been blessed - * Don't complain about order problems with blessed locks + * Pairs of locks which have been blessed. Witness does not complain about + * order problems with blessed lock pairs. Please do not add an entry to the + * table without an explanatory comment. */ static struct witness_blessed blessed_list[] = { + /* + * See the comment in ufs_dirhash.c. Basically, a vnode lock serializes + * both lock orders, so a deadlock cannot happen as a result of this + * LOR. + */ + { "dirhash", "bufwait" }, + + /* + * A UFS vnode may be locked in vget() while a buffer belonging to the + * parent directory vnode is locked. + */ + { "ufs", "bufwait" }, }; -#endif /* * This global is set to 0 once it becomes safe to use the witness code. @@ -1340,17 +1344,7 @@ witness_checkorder(struct lock_object *lock, int flags * We have a lock order violation, check to see if it * is allowed or has already been yelled about. */ -#ifdef BLESSING - /* - * If the lock order is blessed, just bail. We don't - * look for other lock order violations though, which - * may be a bug. - */ - if (blessed(w, w1)) - goto out; -#endif - /* Bail if this violation is known */ if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL) goto out; @@ -1360,6 +1354,14 @@ witness_checkorder(struct lock_object *lock, int flags w_rmatrix[w->w_index][w1->w_index] |= WITNESS_REVERSAL; w->w_reversed = w1->w_reversed = 1; witness_increment_graph_generation(); + + /* + * If the lock order is blessed, bail before logging + * anything. We don't look for other lock order + * violations though, which may be a bug. + */ + if (blessed(w, w1)) + goto out; mtx_unlock_spin(&w_mtx); #ifdef WITNESS_NO_VNODE @@ -2085,7 +2087,6 @@ isitmydescendant(struct witness *ancestor, struct witn __func__)); } -#ifdef BLESSING static int blessed(struct witness *w1, struct witness *w2) { @@ -2105,7 +2106,6 @@ blessed(struct witness *w1, struct witness *w2) } return (0); } -#endif static struct witness * witness_get(void) @@ -2651,6 +2651,9 @@ restart: &tmp_data2->wlod_stack); } mtx_unlock_spin(&w_mtx); + + if (blessed(tmp_w1, tmp_w2)) + continue; sbuf_printf(sb, "\nLock order reversal between \"%s\"(%s) and \"%s\"(%s)!\n",
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