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witness: sleepable rm locks are not sleepable in read mode

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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
This commit is contained in:
Ryan Libby 2019-11-27 01:54:39 +00:00
parent 588e69e2fd
commit 59fb4a95c7
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=355126
3 changed files with 22 additions and 15 deletions
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6
sys/kern/kern_rmlock.c
View File

@ -652,8 +652,8 @@ _rm_rlock_debug(struct rmlock *rm, struct rm_priotracker *tracker,
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_priotracker *tracker,
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)

30
sys/kern/subr_witness.c
View File

@ -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, const char *file,
* 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, const char *file,
* 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, const char *file,
* 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, const char *file,
/*
* 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, const char *file,
*/
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, const char *file, int line)
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, const char *fmt, ...)
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);

1
sys/sys/lock.h
View File

@ -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. */