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| author | Daniel J Blueman <daniel.blueman@gmail.com> | 2010-06-01 14:06:13 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@suse.de> | 2010-09-20 13:18:10 -0700 |
| commit | 0b88f2ba7caa2d0ff6e3521481a82be084ecdc7b (patch) | |
| tree | fe6f9294720b377cd708955e66c56fc5fe35f394 | |
| parent | 58e9934fe305f5c2caeb252cfc478c9111841d6f (diff) | |
sched: apply RCU protection to wake_affine()
commit f3b577dec1f2ce32d2db6d2ca6badff7002512af upstream
The task_group() function returns a pointer that must be protected
by either RCU, the ->alloc_lock, or the cgroup lock (see the
rcu_dereference_check() in task_subsys_state(), which is invoked by
task_group()). The wake_affine() function currently does none of these,
which means that a concurrent update would be within its rights to free
the structure returned by task_group(). Because wake_affine() uses this
structure only to compute load-balancing heuristics, there is no reason
to acquire either of the two locks.
Therefore, this commit introduces an RCU read-side critical section that
starts before the first call to task_group() and ends after the last use
of the "tg" pointer returned from task_group(). Thanks to Li Zefan for
pointing out the need to extend the RCU read-side critical section from
that proposed by the original patch.
Signed-off-by: Daniel J Blueman <daniel.blueman@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
| -rw-r--r-- | kernel/sched_fair.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index d2c46e761fcd..15a3182baeff 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1250,6 +1250,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) * effect of the currently running task from the load * of the current CPU: */ + rcu_read_lock(); if (sync) { tg = task_group(current); weight = current->se.load.weight; @@ -1275,6 +1276,7 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync) balanced = !this_load || 100*(this_load + effective_load(tg, this_cpu, weight, weight)) <= imbalance*(load + effective_load(tg, prev_cpu, 0, weight)); + rcu_read_unlock(); /* * If the currently running task will sleep within |