From d130a177a49c89dbe96190a254f6efbdaf4e982c Mon Sep 17 00:00:00 2001
From: <aidan@DESKTOP-CO5CLN1.localdomain>
Date: Wed, 26 Apr 2017 23:16:52 +0100
Subject: [PATCH] Draft version of a fix for #302. There is no obvious reused
variable to use a temporary seed for each thread, so instead each thread has
a thread-local variable which is uses to seed the rand_r call in
scheduler_enqueue. I need to test this doesn't fail at any point (e.g. if
we're not in a pthread region) but I'm not sure if it would be encountered
outside of a pthread @nnrw56?
---
src/runner.c | 3 ++-
src/scheduler.c | 3 ++-
src/scheduler.h | 2 ++
3 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/src/runner.c b/src/runner.c
index 512a4f362f..dc6cc865a6 100644
--- a/src/runner.c
+++ b/src/runner.c
@@ -1656,7 +1656,8 @@ void *runner_main(void *data) {
struct runner *r = (struct runner *)data;
struct engine *e = r->e;
struct scheduler *sched = &e->sched;
-
+ int seed = r->id
+ pthread_setspecific(sched->local_seed_pointer, &seed);
/* Main loop. */
while (1) {
diff --git a/src/scheduler.c b/src/scheduler.c
index 62fce53762..b75119ffba 100644
--- a/src/scheduler.c
+++ b/src/scheduler.c
@@ -1305,7 +1305,7 @@ void scheduler_enqueue(struct scheduler *s, struct task *t) {
if (qid >= s->nr_queues) error("Bad computed qid.");
/* If no previous owner, pick a random queue. */
- if (qid < 0) qid = rand() % s->nr_queues;
+ if (qid < 0) qid = rand_r((int*)pthread_getspecific(s->local_seed_pointer) ) % s->nr_queues;
/* Increase the waiting counter. */
atomic_inc(&s->waiting);
@@ -1537,6 +1537,7 @@ void scheduler_init(struct scheduler *s, struct space *space, int nr_tasks,
s->size = 0;
s->tasks = NULL;
s->tasks_ind = NULL;
+ pthread_key_create(&s->local_seed_pointer);
scheduler_reset(s, nr_tasks);
}
diff --git a/src/scheduler.h b/src/scheduler.h
index f2225f5f5b..24bf5f105d 100644
--- a/src/scheduler.h
+++ b/src/scheduler.h
@@ -102,6 +102,8 @@ struct scheduler {
/* The node we are working on. */
int nodeID;
+
+ pthread_key_t local_seed_pointer;
};
/* Inlined functions (for speed). */
--
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