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Get rid of kmalloc()

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This changes *NSYNC to allocate waiters on the stack so our locks don't
need to depend on dynamic memory. This make our runtiem simpler, and it
also fixes bugs with thread cancellation support.
This commit is contained in:
Justine Tunney 2023-09-11 21:34:53 -07:00
parent 77a7873057
commit a359de7893
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GPG key ID: BE714B4575D6E328
57 changed files with 405 additions and 472 deletions
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18
third_party/nsync/mem/nsync_mu_wait.c vendored
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@ -149,12 +149,12 @@ int nsync_mu_wait_with_deadline (nsync_mu *mu,
lock_type *l_type;
int first_wait;
int condition_is_true;
waiter *w;
waiter w[1];
int outcome;
/* Work out in which mode the lock is held. */
uint32_t old_word;
IGNORE_RACES_START ();
BLOCK_CANCELLATIONS; /* not supported yet */
BLOCK_CANCELLATIONS;
old_word = ATM_LOAD (&mu->word);
if ((old_word & MU_ANY_LOCK) == 0) {
nsync_panic_ ("nsync_mu not held in some mode when calling "
@ -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;
@ -180,8 +180,10 @@ int nsync_mu_wait_with_deadline (nsync_mu *mu,
int sem_outcome;
unsigned attempts;
int have_lock;
if (w == NULL) {
w = nsync_waiter_new_ (); /* get a waiter struct if we need one. */
/* initialize the waiter if we haven't already */
if (!w->tag) {
nsync_waiter_init_ (w);
}
/* Prepare to wait. */
@ -259,9 +261,7 @@ int nsync_mu_wait_with_deadline (nsync_mu *mu,
}
condition_is_true = (condition == NULL || (*condition) (condition_arg));
}
if (w != NULL) {
nsync_waiter_free_ (w); /* free waiter if we allocated one. */
}
nsync_waiter_destroy_ (w);
if (condition_is_true) {
outcome = 0; /* condition is true trumps other outcomes. */
}
@ -319,5 +319,3 @@ void nsync_mu_unlock_without_wakeup (nsync_mu *mu) {
}
IGNORE_RACES_END ();
}