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authorSergey Senozhatsky <sergey.senozhatsky@gmail.com>2010-11-03 18:52:56 +0200
committerThomas Gleixner <tglx@linutronix.de>2010-11-10 13:07:06 +0100
commitc0deae8c9587419ab13874b74425ce2eb2e18508 (patch)
tree54887135a674951d19e169b5ff17a866b16d7cbe /kernel
parent814ce2521121c2459e16cea8c7221e157edbeddd (diff)
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posix-cpu-timers: Rcu_read_lock/unlock protect find_task_by_vpid call
Commit 4221a9918e38b7494cee341dda7b7b4bb8c04bde "Add RCU check for find_task_by_vpid()" introduced rcu_lockdep_assert to find_task_by_pid_ns. Add rcu_read_lock/rcu_read_unlock to call find_task_by_vpid. Tetsuo Handa wrote: | Quoting from one of posts in that thead | http://kerneltrap.org/mailarchive/linux-kernel/2010/2/8/4536388 | || Usually tasklist gives enough protection, but if copy_process() fails || it calls free_pid() lockless and does call_rcu(delayed_put_pid(). || This means, without rcu lock find_pid_ns() can't scan the hash table || safely. Thomas Gleixner wrote: | We can remove the tasklist_lock while at it. rcu_read_lock is enough. Patch also replaces thread_group_leader with has_group_leader_pid in accordance to comment by Oleg Nesterov: | ... thread_group_leader() check is not relaible without | tasklist. If we race with de_thread() find_task_by_vpid() can find | the new leader before it updates its ->group_leader. | | perhaps it makes sense to change posix_cpu_timer_create() to use | has_group_leader_pid() instead, just to make this code not look racy | and avoid adding new problems. Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Stanislaw Gruszka <sgruszka@redhat.com> Reviewed-by: Oleg Nesterov <oleg@redhat.com> LKML-Reference: <20101103165256.GD30053@swordfish.minsk.epam.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/posix-cpu-timers.c12
1 files changed, 6 insertions, 6 deletions
diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c
index 6842eeba587..05bb7173850 100644
--- a/kernel/posix-cpu-timers.c
+++ b/kernel/posix-cpu-timers.c
@@ -37,13 +37,13 @@ static int check_clock(const clockid_t which_clock)
if (pid == 0)
return 0;
- read_lock(&tasklist_lock);
+ rcu_read_lock();
p = find_task_by_vpid(pid);
if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
- same_thread_group(p, current) : thread_group_leader(p))) {
+ same_thread_group(p, current) : has_group_leader_pid(p))) {
error = -EINVAL;
}
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
return error;
}
@@ -390,7 +390,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
INIT_LIST_HEAD(&new_timer->it.cpu.entry);
- read_lock(&tasklist_lock);
+ rcu_read_lock();
if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
if (pid == 0) {
p = current;
@@ -404,7 +404,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
p = current->group_leader;
} else {
p = find_task_by_vpid(pid);
- if (p && !thread_group_leader(p))
+ if (p && !has_group_leader_pid(p))
p = NULL;
}
}
@@ -414,7 +414,7 @@ int posix_cpu_timer_create(struct k_itimer *new_timer)
} else {
ret = -EINVAL;
}
- read_unlock(&tasklist_lock);
+ rcu_read_unlock();
return ret;
}