From 52ccd88c5e93dcc8bac1dfd67d908660932e8195 Mon Sep 17 00:00:00 2001
From: Pedro Gonnet <gonnet@google.com>
Date: Tue, 31 May 2016 22:11:04 +0200
Subject: [PATCH] make the fast scheduler_addunlock safe again.
---
src/scheduler.c | 43 ++++++++++---------------------------------
src/scheduler.h | 2 +-
2 files changed, 11 insertions(+), 34 deletions(-)
diff --git a/src/scheduler.c b/src/scheduler.c
index 5fc2f6b4b1..c4f84bc72f 100644
--- a/src/scheduler.c
+++ b/src/scheduler.c
@@ -54,39 +54,6 @@
* @param tb The #task that will be unlocked.
*/
-void scheduler_addunlock_old(struct scheduler *s, struct task *ta,
- struct task *tb) {
-
- /* Lock the scheduler since re-allocating the unlocks is not
- thread-safe. */
- if (lock_lock(&s->lock) != 0) error("Unable to lock scheduler.");
-
- /* Does the buffer need to be grown? */
- if (s->nr_unlocks == s->size_unlocks) {
- struct task **unlocks_new;
- int *unlock_ind_new;
- s->size_unlocks *= 2;
- if ((unlocks_new = (struct task **)malloc(
- sizeof(struct task *) *s->size_unlocks)) == NULL ||
- (unlock_ind_new = (int *)malloc(sizeof(int) * s->size_unlocks)) == NULL)
- error("Failed to re-allocate unlocks.");
- memcpy(unlocks_new, s->unlocks, sizeof(struct task *) * s->nr_unlocks);
- memcpy(unlock_ind_new, s->unlock_ind, sizeof(int) * s->nr_unlocks);
- free(s->unlocks);
- free(s->unlock_ind);
- s->unlocks = unlocks_new;
- s->unlock_ind = unlock_ind_new;
- }
-
- /* Write the unlock to the scheduler. */
- const int ind = atomic_inc(&s->nr_unlocks);
- s->unlocks[ind] = tb;
- s->unlock_ind[ind] = ta - s->tasks;
-
- /* Release the scheduler. */
- if (lock_unlock(&s->lock) != 0) error("Unable to unlock scheduler.");
-}
-
void scheduler_addunlock(struct scheduler *s, struct task *ta,
struct task *tb) {
/* Get an index at which to store this unlock. */
@@ -94,6 +61,7 @@ void scheduler_addunlock(struct scheduler *s, struct task *ta,
/* Does the buffer need to be grown? */
if (ind == s->size_unlocks) {
+ /* Allocate the new buffer. */
struct task **unlocks_new;
int *unlock_ind_new;
const int size_unlocks_new = s->size_unlocks * 2;
@@ -101,12 +69,19 @@ void scheduler_addunlock(struct scheduler *s, struct task *ta,
sizeof(struct task *) * size_unlocks_new)) == NULL ||
(unlock_ind_new = (int *)malloc(sizeof(int) * size_unlocks_new)) == NULL)
error("Failed to re-allocate unlocks.");
+
+ /* Wait for all writes to the old buffer to complete. */
+ while (s->completed_unlock_writes < ind);
+
+ /* Copy the buffers. */
memcpy(unlocks_new, s->unlocks, sizeof(struct task *) * ind);
memcpy(unlock_ind_new, s->unlock_ind, sizeof(int) * ind);
free(s->unlocks);
free(s->unlock_ind);
s->unlocks = unlocks_new;
s->unlock_ind = unlock_ind_new;
+
+ /* Publish the new buffer size. */
s->size_unlocks = size_unlocks_new;
}
@@ -116,6 +91,7 @@ void scheduler_addunlock(struct scheduler *s, struct task *ta,
/* Write the unlock to the scheduler. */
s->unlocks[ind] = tb;
s->unlock_ind[ind] = ta - s->tasks;
+ atomic_inc(&s->completed_unlock_writes);
}
/**
@@ -888,6 +864,7 @@ void scheduler_reset(struct scheduler *s, int size) {
s->mask = 0;
s->submask = 0;
s->nr_unlocks = 0;
+ s->completed_unlock_writes = 0;
/* Set the task pointers in the queues. */
for (int k = 0; k < s->nr_queues; k++) s->queues[k].tasks = s->tasks;
diff --git a/src/scheduler.h b/src/scheduler.h
index 4352ec0447..754bfb8c22 100644
--- a/src/scheduler.h
+++ b/src/scheduler.h
@@ -87,7 +87,7 @@ struct scheduler {
/* The task unlocks. */
struct task **volatile unlocks;
int *volatile unlock_ind;
- volatile int nr_unlocks, size_unlocks;
+ volatile int nr_unlocks, size_unlocks, completed_unlock_writes;
/* Lock for this scheduler. */
lock_type lock;
--
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