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Only check the blessings table for known LORs.

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Previously we would check for blessings before marking a given lock
pair as reversed, so each "reversed" lock acquisition would require
a linear scan of the table.  Instead, check the table after marking
the pair as reversed but before generating a report.

Reviewed by:	jhb
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D21135
This commit is contained in:
Mark Johnston 2019-08-02 18:01:47 +00:00
parent ef34be8beb
commit 8675f5f776
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=350540
1 changed files with 11 additions and 8 deletions
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19
sys/kern/subr_witness.c
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@ -1344,14 +1344,6 @@ witness_checkorder(struct lock_object *lock, int flags, const char *file,
* is allowed or has already been yelled about.
*/
/*
* 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;
/* Bail if this violation is known */
if (w_rmatrix[w1->w_index][w->w_index] & WITNESS_REVERSAL)
goto out;
@ -1361,6 +1353,14 @@ witness_checkorder(struct lock_object *lock, int flags, const char *file,
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
@ -2651,6 +2651,9 @@ sbuf_print_witness_badstacks(struct sbuf *sb, size_t *oldidx)
}
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",
tmp_w1->w_name, tmp_w1->w_class->lc_name,