lkml.org 
[lkml]   [2009]   [Dec]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip:sched/urgent] sched: Use rcu in sys_sched_getscheduler/sys_sched_getparam()
Commit-ID:  5fe85be081edf0ac92d83f9c39e0ab5c1371eb82
Gitweb: http://git.kernel.org/tip/5fe85be081edf0ac92d83f9c39e0ab5c1371eb82
Author: Thomas Gleixner <tglx@linutronix.de>
AuthorDate: Wed, 9 Dec 2009 10:14:58 +0000
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 14 Dec 2009 17:11:34 +0100

sched: Use rcu in sys_sched_getscheduler/sys_sched_getparam()

read_lock(&tasklist_lock) does not protect
sys_sched_getscheduler and sys_sched_getparam() against a
concurrent update of the policy or scheduler parameters as
do_sched_setscheduler() does not take the tasklist_lock. The
accessed integers can be retrieved w/o locking and are snapshots
anyway.

Using rcu_read_lock() to protect find_task_by_vpid() and prevent
the task struct from going away is not changing the above
situation.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <20091209100706.753790977@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/sched.c | 10 +++++-----
1 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 258c73c..1782bee 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6458,7 +6458,7 @@ SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
return -EINVAL;

retval = -ESRCH;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
p = find_process_by_pid(pid);
if (p) {
retval = security_task_getscheduler(p);
@@ -6466,7 +6466,7 @@ SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
retval = p->policy
| (p->sched_reset_on_fork ? SCHED_RESET_ON_FORK : 0);
}
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
return retval;
}

@@ -6484,7 +6484,7 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
if (!param || pid < 0)
return -EINVAL;

- read_lock(&tasklist_lock);
+ rcu_read_lock();
p = find_process_by_pid(pid);
retval = -ESRCH;
if (!p)
@@ -6495,7 +6495,7 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
goto out_unlock;

lp.sched_priority = p->rt_priority;
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();

/*
* This one might sleep, we cannot do it with a spinlock held ...
@@ -6505,7 +6505,7 @@ SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
return retval;

out_unlock:
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
return retval;
}


\
 
 \ /
  Last update: 2009-12-14 17:35    [W:0.535 / U:0.040 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site