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Use dynamic memory for *NSYNC waiters

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Justine Tunney 2023-11-10 01:42:06 -08:00
parent 15af5c2d7e
commit 241f949540
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GPG key ID: BE714B4575D6E328
12 changed files with 171 additions and 72 deletions
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50
third_party/nsync/mem/nsync_cv.c vendored
View file

@ -182,7 +182,7 @@ struct nsync_cv_wait_with_deadline_s {
nsync_mu *cv_mu;
nsync_time abs_deadline;
nsync_note cancel_note;
waiter w;
waiter *w;
};
/* Wait until awoken or timeout, or back out of wait if the thread is being cancelled. */
@ -190,11 +190,11 @@ static int nsync_cv_wait_with_deadline_impl_ (struct nsync_cv_wait_with_deadline
int outcome = 0;
int attempts = 0;
IGNORE_RACES_START ();
while (ATM_LOAD_ACQ (&c->w.nw.waiting) != 0) { /* acquire load */
while (ATM_LOAD_ACQ (&c->w->nw.waiting) != 0) { /* acquire load */
if (c->sem_outcome == 0) {
c->sem_outcome = nsync_sem_wait_with_cancel_ (&c->w, c->abs_deadline, c->cancel_note);
c->sem_outcome = nsync_sem_wait_with_cancel_ (c->w, c->abs_deadline, c->cancel_note);
}
if (c->sem_outcome != 0 && ATM_LOAD (&c->w.nw.waiting) != 0) {
if (c->sem_outcome != 0 && ATM_LOAD (&c->w->nw.waiting) != 0) {
/* A timeout or cancellation occurred, and no wakeup.
Acquire *pcv's spinlock, and confirm. */
c->old_word = nsync_spin_test_and_set_ (&c->pcv->word, CV_SPINLOCK,
@ -204,28 +204,28 @@ static int nsync_cv_wait_with_deadline_impl_ (struct nsync_cv_wait_with_deadline
The test of remove_count confirms that the waiter *w
is still governed by *pcv's spinlock; otherwise, some
other thread is about to set w.waiting==0. */
if (ATM_LOAD (&c->w.nw.waiting) != 0) {
if (c->remove_count == ATM_LOAD (&c->w.remove_count)) {
if (ATM_LOAD (&c->w->nw.waiting) != 0) {
if (c->remove_count == ATM_LOAD (&c->w->remove_count)) {
uint32_t old_value;
/* still in cv waiter queue */
/* Not woken, so remove *w from cv
queue, and declare a
timeout/cancellation. */
outcome = c->sem_outcome;
dll_remove (&c->pcv->waiters, &c->w.nw.q);
dll_remove (&c->pcv->waiters, &c->w->nw.q);
do {
old_value = ATM_LOAD (&c->w.remove_count);
} while (!ATM_CAS (&c->w.remove_count, old_value, old_value+1));
old_value = ATM_LOAD (&c->w->remove_count);
} while (!ATM_CAS (&c->w->remove_count, old_value, old_value+1));
if (dll_is_empty (c->pcv->waiters)) {
c->old_word &= ~(CV_NON_EMPTY);
}
ATM_STORE_REL (&c->w.nw.waiting, 0); /* release store */
ATM_STORE_REL (&c->w->nw.waiting, 0); /* release store */
}
}
/* Release spinlock. */
ATM_STORE_REL (&c->pcv->word, c->old_word); /* release store */
}
if (ATM_LOAD (&c->w.nw.waiting) != 0) {
if (ATM_LOAD (&c->w->nw.waiting) != 0) {
/* The delay here causes this thread ultimately to
yield to another that has dequeued this thread, but
has not yet set the waiting field to zero; a
@ -234,10 +234,10 @@ static int nsync_cv_wait_with_deadline_impl_ (struct nsync_cv_wait_with_deadline
attempts = nsync_spin_delay_ (attempts);
}
}
if (c->cv_mu != NULL && c->w.cv_mu == NULL) { /* waiter was moved to *pmu's queue, and woken. */
if (c->cv_mu != NULL && c->w->cv_mu == NULL) { /* waiter was moved to *pmu's queue, and woken. */
/* Requeue on *pmu using existing waiter struct; current thread
is the designated waker. */
nsync_mu_lock_slow_ (c->cv_mu, &c->w, MU_DESIG_WAKER, c->w.l_type);
nsync_mu_lock_slow_ (c->cv_mu, c->w, MU_DESIG_WAKER, c->w->l_type);
} else {
/* Traditional case: We've woken from the cv, and need to reacquire *pmu. */
if (c->is_reader_mu) {
@ -246,7 +246,7 @@ static int nsync_cv_wait_with_deadline_impl_ (struct nsync_cv_wait_with_deadline
(*c->lock) (c->pmu);
}
}
nsync_waiter_destroy_ (&c->w);
nsync_waiter_free_ (c->w);
IGNORE_RACES_END ();
return (outcome);
}
@ -288,7 +288,7 @@ int nsync_cv_wait_with_deadline_generic (nsync_cv *pcv, void *pmu,
struct nsync_cv_wait_with_deadline_s c;
IGNORE_RACES_START ();
nsync_waiter_init_ (&c.w);
c.w = nsync_waiter_new_ ();
c.abs_deadline = abs_deadline;
c.cancel_note = cancel_note;
c.cv_mu = NULL;
@ -296,19 +296,19 @@ int nsync_cv_wait_with_deadline_generic (nsync_cv *pcv, void *pmu,
c.pcv = pcv;
c.pmu = pmu;
ATM_STORE (&c.w.nw.waiting, 1);
c.w.cond.f = NULL; /* Not using a conditional critical section. */
c.w.cond.v = NULL;
c.w.cond.eq = NULL;
ATM_STORE (&c.w->nw.waiting, 1);
c.w->cond.f = NULL; /* Not using a conditional critical section. */
c.w->cond.v = NULL;
c.w->cond.eq = NULL;
if (lock == &void_mu_lock ||
lock == (void (*) (void *)) &nsync_mu_lock ||
lock == (void (*) (void *)) &nsync_mu_rlock) {
c.cv_mu = (nsync_mu *) pmu;
}
c.w.cv_mu = c.cv_mu; /* If *pmu is an nsync_mu, record its address, else record NULL. */
c.w->cv_mu = c.cv_mu; /* If *pmu is an nsync_mu, record its address, else record NULL. */
c.is_reader_mu = 0; /* If true, an nsync_mu in reader mode. */
if (c.cv_mu == NULL) {
c.w.l_type = NULL;
c.w->l_type = NULL;
} else {
uint32_t old_mu_word = ATM_LOAD (&c.cv_mu->word);
int is_writer = (old_mu_word & MU_WHELD_IF_NON_ZERO) != 0;
@ -318,9 +318,9 @@ int nsync_cv_wait_with_deadline_generic (nsync_cv *pcv, void *pmu,
nsync_panic_ ("mu held in reader and writer mode simultaneously "
"on entry to nsync_cv_wait_with_deadline()\n");
}
c.w.l_type = nsync_writer_type_;
c.w->l_type = nsync_writer_type_;
} else if (is_reader) {
c.w.l_type = nsync_reader_type_;
c.w->l_type = nsync_reader_type_;
c.is_reader_mu = 1;
} else {
nsync_panic_ ("mu not held on entry to nsync_cv_wait_with_deadline()\n");
@ -329,8 +329,8 @@ int nsync_cv_wait_with_deadline_generic (nsync_cv *pcv, void *pmu,
/* acquire spinlock, set non-empty */
c.old_word = nsync_spin_test_and_set_ (&pcv->word, CV_SPINLOCK, CV_SPINLOCK|CV_NON_EMPTY, 0);
dll_make_last (&pcv->waiters, &c.w.nw.q);
c.remove_count = ATM_LOAD (&c.w.remove_count);
dll_make_last (&pcv->waiters, &c.w->nw.q);
c.remove_count = ATM_LOAD (&c.w->remove_count);
/* Release the spin lock. */
ATM_STORE_REL (&pcv->word, c.old_word|CV_NON_EMPTY); /* release store */

14
third_party/nsync/mem/nsync_mu_wait.c vendored
View file

@ -149,7 +149,7 @@ int nsync_mu_wait_with_deadline (nsync_mu *mu,
lock_type *l_type;
int first_wait;
int condition_is_true;
waiter w[1];
waiter *w;
int outcome;
/* Work out in which mode the lock is held. */
uint32_t old_word;
@ -165,12 +165,12 @@ int nsync_mu_wait_with_deadline (nsync_mu *mu,
l_type = nsync_reader_type_;
}
w->tag = 0; /* avoid allocating system resources */
first_wait = 1; /* first time through the loop below. */
condition_is_true = (condition == NULL || (*condition) (condition_arg));
/* Loop until either the condition becomes true, or "outcome" indicates
cancellation or timeout. */
w = NULL;
outcome = 0;
while (outcome == 0 && !condition_is_true) {
uint32_t has_condition;
@ -180,10 +180,8 @@ int nsync_mu_wait_with_deadline (nsync_mu *mu,
int sem_outcome;
unsigned attempts;
int have_lock;
/* initialize the waiter if we haven't already */
if (!w->tag) {
nsync_waiter_init_ (w);
if (w == NULL) {
w = nsync_waiter_new_ (); /* get a waiter struct if we need one. */
}
/* Prepare to wait. */
@ -261,7 +259,9 @@ int nsync_mu_wait_with_deadline (nsync_mu *mu,
}
condition_is_true = (condition == NULL || (*condition) (condition_arg));
}
nsync_waiter_destroy_ (w);
if (w != NULL) {
nsync_waiter_free_ (w); /* free waiter if we allocated one. */
}
if (condition_is_true) {
outcome = 0; /* condition is true trumps other outcomes. */
}

5
third_party/nsync/mem/nsync_wait.c vendored
View file

@ -49,8 +49,7 @@ int nsync_wait_n (void *mu, void (*lock) (void *), void (*unlock) (void *),
int unlocked = 0;
int j;
int enqueued = 1;
waiter w[1];
nsync_waiter_init_ (w);
waiter *w = nsync_waiter_new_ ();
struct nsync_waiter_s nw_set[4];
struct nsync_waiter_s *nw = nw_set;
if (count > (int) (sizeof (nw_set) / sizeof (nw_set[0]))) {
@ -97,10 +96,10 @@ int nsync_wait_n (void *mu, void (*lock) (void *), void (*unlock) (void *),
}
}
nsync_waiter_destroy_ (w);
if (nw != nw_set) {
free (nw);
}
nsync_waiter_free_ (w);
if (unlocked) {
(*lock) (mu);
}