Messages in this thread Patch in this message | | | Date | Tue, 2 Nov 2010 18:02:23 +0200 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH] posix-cpu-timers: rcu_read_lock/unlock protect find_task_by_vpid call |
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On (11/02/10 16:31), Thomas Gleixner wrote: > On Tue, 2 Nov 2010, Sergey Senozhatsky wrote: > > > 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. > > We can remove the tasklist_lock while at it. rcu_read_lock is enough. >
Please kindly review.
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diff --git a/kernel/posix-cpu-timers.c b/kernel/posix-cpu-timers.c index 6842eeb..96fe2a3 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))) { 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; @@ -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; } [unhandled content-type:application/pgp-signature] | |