diff options
| author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2010-10-06 17:32:51 -0700 |
|---|---|---|
| committer | Paul Gortmaker <paul.gortmaker@windriver.com> | 2011-06-26 12:46:38 -0400 |
| commit | b431734a04719c217a39a2219bf071774facf250 (patch) | |
| tree | 3c8ef9130a3d6e0d40f4c89f55bda0af3894c4b6 /kernel | |
| parent | 6043c01d813bc3fc21a289461a1a75082516d49b (diff) | |
sched: suppress RCU lockdep splat in task_fork_fair
commit b0a0f667a349247bd7f05f806b662a25653822bc upstream.
> ===================================================
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> /home/greearb/git/linux.wireless-testing/kernel/sched.c:618 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 1, debug_locks = 1
> 1 lock held by ifup/23517:
> #0: (&rq->lock){-.-.-.}, at: [<c042f782>] task_fork_fair+0x3b/0x108
>
> stack backtrace:
> Pid: 23517, comm: ifup Not tainted 2.6.36-rc6-wl+ #5
> Call Trace:
> [<c075e219>] ? printk+0xf/0x16
> [<c0455842>] lockdep_rcu_dereference+0x74/0x7d
> [<c0426854>] task_group+0x6d/0x79
> [<c042686e>] set_task_rq+0xe/0x57
> [<c042f79e>] task_fork_fair+0x57/0x108
> [<c042e965>] sched_fork+0x82/0xf9
> [<c04334b3>] copy_process+0x569/0xe8e
> [<c0433ef0>] do_fork+0x118/0x262
> [<c076302f>] ? do_page_fault+0x16a/0x2cf
> [<c044b80c>] ? up_read+0x16/0x2a
> [<c04085ae>] sys_clone+0x1b/0x20
> [<c04030a5>] ptregs_clone+0x15/0x30
> [<c0402f1c>] ? sysenter_do_call+0x12/0x38
Here a newly created task is having its runqueue assigned. The new task
is not yet on the tasklist, so cannot go away. This is therefore a false
positive, suppress with an RCU read-side critical section.
Reported-by: Ben Greear <greearb@candelatech.com
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Tested-by: Ben Greear <greearb@candelatech.com
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched_fair.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index 3a0f7baa5485..b0f6803562b8 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -3592,8 +3592,11 @@ static void task_fork_fair(struct task_struct *p) update_rq_clock(rq); - if (unlikely(task_cpu(p) != this_cpu)) + if (unlikely(task_cpu(p) != this_cpu)) { + rcu_read_lock(); __set_task_cpu(p, this_cpu); + rcu_read_unlock(); + } update_curr(cfs_rq); |