Commit-ID: 23f5d142519621b16cf2b378cf8adf4dcf01a616
Gitweb: http://git.kernel.org/tip/23f5d142519621b16cf2b378cf8adf4dcf01a616
Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Wed, 9 Dec 2009 10:15:01 +0000
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Mon, 14 Dec 2009 17:11:35 +0100
sched: Use rcu in sched_get/set_affinity()
tasklist_lock is held read locked to protect the
find_task_by_vpid() call and to prevent the task going away.
sched_setaffinity acquires a task struct ref and drops tasklist
lock right away. The access to the cpus_allowed mask is
protected by rq->lock.
rcu_read_lock() provides the same protection here.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
LKML-Reference: <20091209100706.789059966@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/sched.c | 16 ++++++----------
1 files changed, 6 insertions(+), 10 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 1782bee..7989312 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6516,22 +6516,18 @@ long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
int retval;
get_online_cpus();
- read_lock(&tasklist_lock);
+ rcu_read_lock();
p = find_process_by_pid(pid);
if (!p) {
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
put_online_cpus();
return -ESRCH;
}
- /*
- * It is not safe to call set_cpus_allowed with the
- * tasklist_lock held. We will bump the task_struct's
- * usage count and then drop tasklist_lock.
- */
+ /* Prevent p going away */
get_task_struct(p);
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) {
retval = -ENOMEM;
@@ -6617,7 +6613,7 @@ long sched_getaffinity(pid_t pid, struct cpumask *mask)
int retval;
get_online_cpus();
- read_lock(&tasklist_lock);
+ rcu_read_lock();
retval = -ESRCH;
p = find_process_by_pid(pid);
@@ -6633,7 +6629,7 @@ long sched_getaffinity(pid_t pid, struct cpumask *mask)
task_rq_unlock(rq, &flags);
out_unlock:
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
put_online_cpus();
return retval;
--
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