From 23f5d142519621b16cf2b378cf8adf4dcf01a616 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 9 Dec 2009 10:15:01 +0000 Subject: [PATCH] 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 Cc: Peter Zijlstra LKML-Reference: <20091209100706.789059966@linutronix.de> Signed-off-by: Ingo Molnar --- kernel/sched.c | 16 ++++++---------- 1 file changed, 6 insertions(+), 10 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 1782beed2fa7..79893123325c 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; -- 2.20.1