svn commit: r355126 - in head/sys: kern sys
Ryan Libby
rlibby at FreeBSD.org
Wed Nov 27 01:54:40 UTC 2019
Author: rlibby
Date: Wed Nov 27 01:54:39 2019
New Revision: 355126
URL: https://svnweb.freebsd.org/changeset/base/355126
Log:
witness: sleepable rm locks are not sleepable in read mode
There are two classes of rm lock, one "sleepable" and one not. But even
a "sleepable" rm lock is only sleepable in write mode, and is
non-sleepable when taken in read mode.
Warn about sleepable rm locks in read mode as non-sleepable locks. Do
this by defining a new lock operation flag, LOP_NOSLEEP, to indicate
that a lock is non-sleepable despite what the LO_SLEEPABLE flag would
indicate, and defining a new witness lock instance flag, LI_SLEEPABLE,
to track the product of LO_SLEEPABLE and LOP_NOSLEEP on the lock
instance.
Reviewed by: markj
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D22527
Modified:
head/sys/kern/kern_rmlock.c
head/sys/kern/subr_witness.c
head/sys/sys/lock.h
Modified: head/sys/kern/kern_rmlock.c
==============================================================================
--- head/sys/kern/kern_rmlock.c Wed Nov 27 01:21:42 2019 (r355125)
+++ head/sys/kern/kern_rmlock.c Wed Nov 27 01:54:39 2019 (r355126)
@@ -652,8 +652,8 @@ _rm_rlock_debug(struct rmlock *rm, struct rm_priotrack
KASSERT(!rm_wowned(rm),
("rm_rlock: wlock already held for %s @ %s:%d",
rm->lock_object.lo_name, file, line));
- WITNESS_CHECKORDER(&rm->lock_object, LOP_NEWORDER, file, line,
- NULL);
+ WITNESS_CHECKORDER(&rm->lock_object,
+ LOP_NEWORDER | LOP_NOSLEEP, file, line, NULL);
}
if (_rm_rlock(rm, tracker, trylock)) {
@@ -663,7 +663,7 @@ _rm_rlock_debug(struct rmlock *rm, struct rm_priotrack
else
LOCK_LOG_LOCK("RMRLOCK", &rm->lock_object, 0, 0, file,
line);
- WITNESS_LOCK(&rm->lock_object, 0, file, line);
+ WITNESS_LOCK(&rm->lock_object, LOP_NOSLEEP, file, line);
TD_LOCKS_INC(curthread);
return (1);
} else if (trylock)
Modified: head/sys/kern/subr_witness.c
==============================================================================
--- head/sys/kern/subr_witness.c Wed Nov 27 01:21:42 2019 (r355125)
+++ head/sys/kern/subr_witness.c Wed Nov 27 01:54:39 2019 (r355126)
@@ -131,6 +131,7 @@ __FBSDID("$FreeBSD$");
#define LI_RECURSEMASK 0x0000ffff /* Recursion depth of lock instance. */
#define LI_EXCLUSIVE 0x00010000 /* Exclusive lock instance. */
#define LI_NORELEASE 0x00020000 /* Lock not allowed to be released. */
+#define LI_SLEEPABLE 0x00040000 /* Lock may be held while sleeping. */
#ifndef WITNESS_COUNT
#define WITNESS_COUNT 1536
@@ -1302,7 +1303,7 @@ witness_checkorder(struct lock_object *lock, int flags
* If we are locking Giant and this is a sleepable
* lock, then skip it.
*/
- if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0 &&
+ if ((lock1->li_flags & LI_SLEEPABLE) != 0 &&
lock == &Giant.lock_object)
continue;
@@ -1311,6 +1312,7 @@ witness_checkorder(struct lock_object *lock, int flags
* is Giant, then skip it.
*/
if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
+ (flags & LOP_NOSLEEP) == 0 &&
lock1->li_lock == &Giant.lock_object)
continue;
@@ -1320,15 +1322,16 @@ witness_checkorder(struct lock_object *lock, int flags
* order violation to enfore a general lock order of
* sleepable locks before non-sleepable locks.
*/
- if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
- (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
+ if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
+ (flags & LOP_NOSLEEP) == 0 &&
+ (lock1->li_flags & LI_SLEEPABLE) == 0)
goto reversal;
/*
* If we are locking Giant and this is a non-sleepable
* lock, then treat it as a reversal.
*/
- if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0 &&
+ if ((lock1->li_flags & LI_SLEEPABLE) == 0 &&
lock == &Giant.lock_object)
goto reversal;
@@ -1378,11 +1381,12 @@ witness_checkorder(struct lock_object *lock, int flags
/*
* Ok, yell about it.
*/
- if (((lock->lo_flags & LO_SLEEPABLE) != 0 &&
- (lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0))
+ if ((lock->lo_flags & LO_SLEEPABLE) != 0 &&
+ (flags & LOP_NOSLEEP) == 0 &&
+ (lock1->li_flags & LI_SLEEPABLE) == 0)
witness_output(
"lock order reversal: (sleepable after non-sleepable)\n");
- else if ((lock1->li_lock->lo_flags & LO_SLEEPABLE) == 0
+ else if ((lock1->li_flags & LI_SLEEPABLE) == 0
&& lock == &Giant.lock_object)
witness_output(
"lock order reversal: (Giant after non-sleepable)\n");
@@ -1440,7 +1444,8 @@ witness_checkorder(struct lock_object *lock, int flags
*/
if (flags & LOP_NEWORDER &&
!(plock->li_lock == &Giant.lock_object &&
- (lock->lo_flags & LO_SLEEPABLE) != 0)) {
+ (lock->lo_flags & LO_SLEEPABLE) != 0 &&
+ (flags & LOP_NOSLEEP) == 0)) {
CTR3(KTR_WITNESS, "%s: adding %s as a child of %s", __func__,
w->w_name, plock->li_lock->lo_witness->w_name);
itismychild(plock->li_lock->lo_witness, w);
@@ -1500,10 +1505,11 @@ witness_lock(struct lock_object *lock, int flags, cons
instance->li_lock = lock;
instance->li_line = line;
instance->li_file = file;
+ instance->li_flags = 0;
if ((flags & LOP_EXCLUSIVE) != 0)
- instance->li_flags = LI_EXCLUSIVE;
- else
- instance->li_flags = 0;
+ instance->li_flags |= LI_EXCLUSIVE;
+ if ((lock->lo_flags & LO_SLEEPABLE) != 0 && (flags & LOP_NOSLEEP) == 0)
+ instance->li_flags |= LI_SLEEPABLE;
CTR4(KTR_WITNESS, "%s: pid %d added %s as lle[%d]", __func__,
td->td_proc->p_pid, lock->lo_name, lle->ll_count - 1);
}
@@ -1763,7 +1769,7 @@ witness_warn(int flags, struct lock_object *lock, cons
lock1->li_lock == &Giant.lock_object)
continue;
if (flags & WARN_SLEEPOK &&
- (lock1->li_lock->lo_flags & LO_SLEEPABLE) != 0)
+ (lock1->li_flags & LI_SLEEPABLE) != 0)
continue;
if (n == 0) {
va_start(ap, fmt);
Modified: head/sys/sys/lock.h
==============================================================================
--- head/sys/sys/lock.h Wed Nov 27 01:21:42 2019 (r355125)
+++ head/sys/sys/lock.h Wed Nov 27 01:54:39 2019 (r355126)
@@ -107,6 +107,7 @@ struct lock_class {
#define LOP_TRYLOCK 0x00000004 /* Don't check lock order. */
#define LOP_EXCLUSIVE 0x00000008 /* Exclusive lock. */
#define LOP_DUPOK 0x00000010 /* Don't check for duplicate acquires */
+#define LOP_NOSLEEP 0x00000020 /* Non-sleepable despite LO_SLEEPABLE */
/* Flags passed to witness_assert. */
#define LA_MASKASSERT 0x000000ff /* Mask for witness defined asserts. */
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