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Code Issues Releases Activity

Fix up priority propagation:

Browse Source 
- Use a better test for determining when a process is running.
- Convert some checks to assertions.
- Remove unnecessary tests.
- Save the priority before acquiring a mutex rather than in msleep(9).
This commit is contained in:
John Baldwin 2000-11-30 00:51:16 +00:00
parent 7f18d5d343
commit 1bd0eefb4c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=69376
4 changed files with 180 additions and 73 deletions
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84
sys/kern/kern_mutex.c
View File

@ -102,7 +102,7 @@ static int mtx_max_cnt;
void _mtx_enter_giant_def(void);
void _mtx_exit_giant_def(void);
static void propagate_priority(struct proc *) __unused;
static void propagate_priority(struct proc *);
#define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
#define mtx_owner(m) (mtx_unowned(m) ? NULL \
@ -135,6 +135,7 @@ propagate_priority(struct proc *p)
int pri = p->p_priority;
struct mtx *m = p->p_blocked;
mtx_assert(&sched_lock, MA_OWNED);
for (;;) {
struct proc *p1;
@ -150,37 +151,57 @@ propagate_priority(struct proc *p)
return;
}
MPASS(p->p_magic == P_MAGIC);
KASSERT(p->p_stat != SSLEEP, ("sleeping process owns a mutex"));
if (p->p_priority <= pri)
return;
/*
* Bump this process' priority.
*/
SET_PRIO(p, pri);
/*
* If lock holder is actually running, just bump priority.
*/
if (TAILQ_NEXT(p, p_procq) == NULL) {
#ifdef SMP
/*
* For SMP, we can check the p_oncpu field to see if we are
* running.
*/
if (p->p_oncpu != 0xff) {
MPASS(p->p_stat == SRUN || p->p_stat == SZOMB);
SET_PRIO(p, pri);
return;
}
#else
/*
* For UP, we check to see if p is curproc (this shouldn't
* ever happen however as it would mean we are in a deadlock.)
*/
if (p == curproc) {
panic("Deadlock detected");
return;
}
#endif
/*
* If on run queue move to new run queue, and
* quit.
*/
if (p->p_stat == SRUN) {
printf("XXX: moving process %d(%s) to a new run queue\n",
p->p_pid, p->p_comm);
MPASS(p->p_blocked == NULL);
remrunqueue(p);
SET_PRIO(p, pri);
setrunqueue(p);
return;
}
/*
* If we aren't blocked on a mutex, give up and quit.
* If we aren't blocked on a mutex, we should be.
*/
if (p->p_stat != SMTX) {
printf(
"XXX: process %d(%s):%d holds %s but isn't blocked on a mutex\n",
p->p_pid, p->p_comm, p->p_stat, m->mtx_description);
return;
}
KASSERT(p->p_stat == SMTX, (
"process %d(%s):%d holds %s but isn't blocked on a mutex\n",
p->p_pid, p->p_comm, p->p_stat,
m->mtx_description));
/*
* Pick up the mutex that p is blocked on.
@ -194,19 +215,24 @@ propagate_priority(struct proc *p)
* Check if the proc needs to be moved up on
* the blocked chain
*/
if ((p1 = TAILQ_PREV(p, rq, p_procq)) == NULL ||
p1->p_priority <= pri) {
if (p1)
printf(
if (p == TAILQ_FIRST(&m->mtx_blocked)) {
printf("XXX: process at head of run queue\n");
continue;
}
p1 = TAILQ_PREV(p, rq, p_procq);
if (p1->p_priority <= pri) {
printf(
"XXX: previous process %d(%s) has higher priority\n",
p->p_pid, p->p_comm);
else
printf("XXX: process at head of run queue\n");
p->p_pid, p->p_comm);
continue;
}
/*
* Remove proc from blocked chain
* Remove proc from blocked chain and determine where
* it should be moved up to. Since we know that p1 has
* a lower priority than p, we know that at least one
* process in the chain has a lower priority and that
* p1 will thus not be NULL after the loop.
*/
TAILQ_REMOVE(&m->mtx_blocked, p, p_procq);
TAILQ_FOREACH(p1, &m->mtx_blocked, p_procq) {
@ -214,12 +240,10 @@ propagate_priority(struct proc *p)
if (p1->p_priority > pri)
break;
}
if (p1)
TAILQ_INSERT_BEFORE(p1, p, p_procq);
else
TAILQ_INSERT_TAIL(&m->mtx_blocked, p, p_procq);
MPASS(p1 != NULL);
TAILQ_INSERT_BEFORE(p1, p, p_procq);
CTR4(KTR_LOCK,
"propagate priority: p 0x%p moved before 0x%p on [0x%p] %s",
"propagate_priority: p 0x%p moved before 0x%p on [0x%p] %s",
p, p1, m, m->mtx_description);
}
}
@ -241,6 +265,18 @@ mtx_enter_hard(struct mtx *m, int type, int saveintr)
}
CTR3(KTR_LOCK, "mtx_enter: 0x%p contested (lock=%p) [0x%p]",
m, (void *)m->mtx_lock, (void *)RETIP(m));
/*
* Save our priority. Even though p_nativepri is protected
* by sched_lock, we don't obtain it here as it can be
* expensive. Since this is the only place p_nativepri is
* set, and since two CPUs will not be executing the same
* process concurrently, we know that no other CPU is going
* to be messing with this. Also, p_nativepri is only read
* when we are blocked on a mutex, so that can't be happening
* right now either.
*/
p->p_nativepri = p->p_priority;
while (!_obtain_lock(m, p)) {
uintptr_t v;
struct proc *p1;

1
sys/kern/kern_synch.c
View File

@ -464,7 +464,6 @@ msleep(ident, mtx, priority, wmesg, timo)
p->p_wmesg = wmesg;
p->p_slptime = 0;
p->p_priority = priority & PRIMASK;
p->p_nativepri = p->p_priority;
CTR4(KTR_PROC, "msleep: proc %p (pid %d, %s), schedlock %p",
p, p->p_pid, p->p_comm, (void *) sched_lock.mtx_lock);
TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], p, p_slpq);

84
sys/kern/subr_turnstile.c
View File

@ -102,7 +102,7 @@ static int mtx_max_cnt;
void _mtx_enter_giant_def(void);
void _mtx_exit_giant_def(void);
static void propagate_priority(struct proc *) __unused;
static void propagate_priority(struct proc *);
#define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
#define mtx_owner(m) (mtx_unowned(m) ? NULL \
@ -135,6 +135,7 @@ propagate_priority(struct proc *p)
int pri = p->p_priority;
struct mtx *m = p->p_blocked;
mtx_assert(&sched_lock, MA_OWNED);
for (;;) {
struct proc *p1;
@ -150,37 +151,57 @@ propagate_priority(struct proc *p)
return;
}
MPASS(p->p_magic == P_MAGIC);
KASSERT(p->p_stat != SSLEEP, ("sleeping process owns a mutex"));
if (p->p_priority <= pri)
return;
/*
* Bump this process' priority.
*/
SET_PRIO(p, pri);
/*
* If lock holder is actually running, just bump priority.
*/
if (TAILQ_NEXT(p, p_procq) == NULL) {
#ifdef SMP
/*
* For SMP, we can check the p_oncpu field to see if we are
* running.
*/
if (p->p_oncpu != 0xff) {
MPASS(p->p_stat == SRUN || p->p_stat == SZOMB);
SET_PRIO(p, pri);
return;
}
#else
/*
* For UP, we check to see if p is curproc (this shouldn't
* ever happen however as it would mean we are in a deadlock.)
*/
if (p == curproc) {
panic("Deadlock detected");
return;
}
#endif
/*
* If on run queue move to new run queue, and
* quit.
*/
if (p->p_stat == SRUN) {
printf("XXX: moving process %d(%s) to a new run queue\n",
p->p_pid, p->p_comm);
MPASS(p->p_blocked == NULL);
remrunqueue(p);
SET_PRIO(p, pri);
setrunqueue(p);
return;
}
/*
* If we aren't blocked on a mutex, give up and quit.
* If we aren't blocked on a mutex, we should be.
*/
if (p->p_stat != SMTX) {
printf(
"XXX: process %d(%s):%d holds %s but isn't blocked on a mutex\n",
p->p_pid, p->p_comm, p->p_stat, m->mtx_description);
return;
}
KASSERT(p->p_stat == SMTX, (
"process %d(%s):%d holds %s but isn't blocked on a mutex\n",
p->p_pid, p->p_comm, p->p_stat,
m->mtx_description));
/*
* Pick up the mutex that p is blocked on.
@ -194,19 +215,24 @@ propagate_priority(struct proc *p)
* Check if the proc needs to be moved up on
* the blocked chain
*/
if ((p1 = TAILQ_PREV(p, rq, p_procq)) == NULL ||
p1->p_priority <= pri) {
if (p1)
printf(
if (p == TAILQ_FIRST(&m->mtx_blocked)) {
printf("XXX: process at head of run queue\n");
continue;
}
p1 = TAILQ_PREV(p, rq, p_procq);
if (p1->p_priority <= pri) {
printf(
"XXX: previous process %d(%s) has higher priority\n",
p->p_pid, p->p_comm);
else
printf("XXX: process at head of run queue\n");
p->p_pid, p->p_comm);
continue;
}
/*
* Remove proc from blocked chain
* Remove proc from blocked chain and determine where
* it should be moved up to. Since we know that p1 has
* a lower priority than p, we know that at least one
* process in the chain has a lower priority and that
* p1 will thus not be NULL after the loop.
*/
TAILQ_REMOVE(&m->mtx_blocked, p, p_procq);
TAILQ_FOREACH(p1, &m->mtx_blocked, p_procq) {
@ -214,12 +240,10 @@ propagate_priority(struct proc *p)
if (p1->p_priority > pri)
break;
}
if (p1)
TAILQ_INSERT_BEFORE(p1, p, p_procq);
else
TAILQ_INSERT_TAIL(&m->mtx_blocked, p, p_procq);
MPASS(p1 != NULL);
TAILQ_INSERT_BEFORE(p1, p, p_procq);
CTR4(KTR_LOCK,
"propagate priority: p 0x%p moved before 0x%p on [0x%p] %s",
"propagate_priority: p 0x%p moved before 0x%p on [0x%p] %s",
p, p1, m, m->mtx_description);
}
}
@ -241,6 +265,18 @@ mtx_enter_hard(struct mtx *m, int type, int saveintr)
}
CTR3(KTR_LOCK, "mtx_enter: 0x%p contested (lock=%p) [0x%p]",
m, (void *)m->mtx_lock, (void *)RETIP(m));
/*
* Save our priority. Even though p_nativepri is protected
* by sched_lock, we don't obtain it here as it can be
* expensive. Since this is the only place p_nativepri is
* set, and since two CPUs will not be executing the same
* process concurrently, we know that no other CPU is going
* to be messing with this. Also, p_nativepri is only read
* when we are blocked on a mutex, so that can't be happening
* right now either.
*/
p->p_nativepri = p->p_priority;
while (!_obtain_lock(m, p)) {
uintptr_t v;
struct proc *p1;

84
sys/kern/subr_witness.c
View File

@ -102,7 +102,7 @@ static int mtx_max_cnt;
void _mtx_enter_giant_def(void);
void _mtx_exit_giant_def(void);
static void propagate_priority(struct proc *) __unused;
static void propagate_priority(struct proc *);
#define mtx_unowned(m) ((m)->mtx_lock == MTX_UNOWNED)
#define mtx_owner(m) (mtx_unowned(m) ? NULL \
@ -135,6 +135,7 @@ propagate_priority(struct proc *p)
int pri = p->p_priority;
struct mtx *m = p->p_blocked;
mtx_assert(&sched_lock, MA_OWNED);
for (;;) {
struct proc *p1;
@ -150,37 +151,57 @@ propagate_priority(struct proc *p)
return;
}
MPASS(p->p_magic == P_MAGIC);
KASSERT(p->p_stat != SSLEEP, ("sleeping process owns a mutex"));
if (p->p_priority <= pri)
return;
/*
* Bump this process' priority.
*/
SET_PRIO(p, pri);
/*
* If lock holder is actually running, just bump priority.
*/
if (TAILQ_NEXT(p, p_procq) == NULL) {
#ifdef SMP
/*
* For SMP, we can check the p_oncpu field to see if we are
* running.
*/
if (p->p_oncpu != 0xff) {
MPASS(p->p_stat == SRUN || p->p_stat == SZOMB);
SET_PRIO(p, pri);
return;
}
#else
/*
* For UP, we check to see if p is curproc (this shouldn't
* ever happen however as it would mean we are in a deadlock.)
*/
if (p == curproc) {
panic("Deadlock detected");
return;
}
#endif
/*
* If on run queue move to new run queue, and
* quit.
*/
if (p->p_stat == SRUN) {
printf("XXX: moving process %d(%s) to a new run queue\n",
p->p_pid, p->p_comm);
MPASS(p->p_blocked == NULL);
remrunqueue(p);
SET_PRIO(p, pri);
setrunqueue(p);
return;
}
/*
* If we aren't blocked on a mutex, give up and quit.
* If we aren't blocked on a mutex, we should be.
*/
if (p->p_stat != SMTX) {
printf(
"XXX: process %d(%s):%d holds %s but isn't blocked on a mutex\n",
p->p_pid, p->p_comm, p->p_stat, m->mtx_description);
return;
}
KASSERT(p->p_stat == SMTX, (
"process %d(%s):%d holds %s but isn't blocked on a mutex\n",
p->p_pid, p->p_comm, p->p_stat,
m->mtx_description));
/*
* Pick up the mutex that p is blocked on.
@ -194,19 +215,24 @@ propagate_priority(struct proc *p)
* Check if the proc needs to be moved up on
* the blocked chain
*/
if ((p1 = TAILQ_PREV(p, rq, p_procq)) == NULL ||
p1->p_priority <= pri) {
if (p1)
printf(
if (p == TAILQ_FIRST(&m->mtx_blocked)) {
printf("XXX: process at head of run queue\n");
continue;
}
p1 = TAILQ_PREV(p, rq, p_procq);
if (p1->p_priority <= pri) {
printf(
"XXX: previous process %d(%s) has higher priority\n",
p->p_pid, p->p_comm);
else
printf("XXX: process at head of run queue\n");
p->p_pid, p->p_comm);
continue;
}
/*
* Remove proc from blocked chain
* Remove proc from blocked chain and determine where
* it should be moved up to. Since we know that p1 has
* a lower priority than p, we know that at least one
* process in the chain has a lower priority and that
* p1 will thus not be NULL after the loop.
*/
TAILQ_REMOVE(&m->mtx_blocked, p, p_procq);
TAILQ_FOREACH(p1, &m->mtx_blocked, p_procq) {
@ -214,12 +240,10 @@ propagate_priority(struct proc *p)
if (p1->p_priority > pri)
break;
}
if (p1)
TAILQ_INSERT_BEFORE(p1, p, p_procq);
else
TAILQ_INSERT_TAIL(&m->mtx_blocked, p, p_procq);
MPASS(p1 != NULL);
TAILQ_INSERT_BEFORE(p1, p, p_procq);
CTR4(KTR_LOCK,
"propagate priority: p 0x%p moved before 0x%p on [0x%p] %s",
"propagate_priority: p 0x%p moved before 0x%p on [0x%p] %s",
p, p1, m, m->mtx_description);
}
}
@ -241,6 +265,18 @@ mtx_enter_hard(struct mtx *m, int type, int saveintr)
}
CTR3(KTR_LOCK, "mtx_enter: 0x%p contested (lock=%p) [0x%p]",
m, (void *)m->mtx_lock, (void *)RETIP(m));
/*
* Save our priority. Even though p_nativepri is protected
* by sched_lock, we don't obtain it here as it can be
* expensive. Since this is the only place p_nativepri is
* set, and since two CPUs will not be executing the same
* process concurrently, we know that no other CPU is going
* to be messing with this. Also, p_nativepri is only read
* when we are blocked on a mutex, so that can't be happening
* right now either.
*/
p->p_nativepri = p->p_priority;
while (!_obtain_lock(m, p)) {
uintptr_t v;
struct proc *p1;