On 03/20/2013 03:55 PM, Rik van Riel wrote:
> Include lkml in the CC: this time... *sigh*
> ---8<---
>
> This series makes the sysv semaphore code more scalable,
> by reducing the time the semaphore lock is held, and making
> the locking more scalable for semaphore arrays with multiple
> semaphores.
Hi Rik,
I'm getting the following false positives from lockdep:
[ 80.492995] =============================================
[ 80.494052] [ INFO: possible recursive locking detected ]
[ 80.494878] 3.9.0-rc4-next-20130325-sasha-00044-gcb6ef58 #315 Tainted: G
W
[ 80.496228] ---------------------------------------------
[ 80.497171] trinity-child9/7210 is trying to acquire lock:
[ 80.497934] (&(&sma->sem_base[i].lock)->rlock){+.+...}, at:
[<ffffffff8192da37>] newary+0x1c7/0x2a0
[ 80.499202]
[ 80.499202] but task is already holding lock:
[ 80.500031] (&(&sma->sem_base[i].lock)->rlock){+.+...}, at:
[<ffffffff8192da37>] newary+0x1c7/0x2a0
[ 80.500031]
[ 80.500031] other info that might help us debug this:
[ 80.500031] Possible unsafe locking scenario:
[ 80.500031]
[ 80.500031] CPU0
[ 80.500031] ----
[ 80.500031] lock(&(&sma->sem_base[i].lock)->rlock);
[ 80.500031] lock(&(&sma->sem_base[i].lock)->rlock);
[ 80.500031]
[ 80.500031] *** DEADLOCK ***
[ 80.500031]
[ 80.500031] May be due to missing lock nesting notation
[ 80.500031]
[ 80.500031] 4 locks held by trinity-child9/7210:
[ 80.500031] #0: (&ids->rw_mutex){+++++.}, at: [<ffffffff8192a422>]
ipcget+0x72/0x340
[ 80.500031] #1: (rcu_read_lock){.+.+..}, at: [<ffffffff81929b65>]
ipc_addid+0x35/0x230
[ 80.500031] #2: (&(&new->lock)->rlock){+.+...}, at: [<ffffffff81929c00>]
ipc_addid+0xd0/0x230
[ 80.500031] #3: (&(&sma->sem_base[i].lock)->rlock){+.+...}, at:
[<ffffffff8192da37>] newary+0x1c7/0x2a0
[ 80.500031]
[ 80.500031] stack backtrace:
[ 80.500031] Pid: 7210, comm: trinity-child9 Tainted: G W
3.9.0-rc4-next-20130325-sasha-00044-gcb6ef58 #315
[ 80.500031] Call Trace:
[ 80.500031] [<ffffffff8117f65e>] __lock_acquire+0xc6e/0x1e50
[ 80.500031] [<ffffffff819ff225>] ? idr_get_empty_slot+0x255/0x3c0
[ 80.500031] [<ffffffff8117ca1e>] ? mark_held_locks+0x12e/0x150
[ 80.500031] [<ffffffff811810ba>] lock_acquire+0x1aa/0x240
[ 80.500031] [<ffffffff8192da37>] ? newary+0x1c7/0x2a0
[ 80.500031] [<ffffffff83d8768b>] _raw_spin_lock+0x3b/0x70
[ 80.500031] [<ffffffff8192da37>] ? newary+0x1c7/0x2a0
[ 80.500031] [<ffffffff8192da37>] newary+0x1c7/0x2a0
[ 80.500031] [<ffffffff8192a422>] ? ipcget+0x72/0x340
[ 80.500031] [<ffffffff8192a5d6>] ipcget+0x226/0x340
[ 80.500031] [<ffffffff81930215>] SyS_semget+0x65/0x80
[ 80.500031] [<ffffffff8192d870>] ? semctl_down.constprop.8+0x320/0x320
[ 80.500031] [<ffffffff8192c770>] ? wake_up_sem_queue_do+0xa0/0xa0
[ 80.500031] [<ffffffff8192c690>] ? SyS_msgrcv+0x20/0x20
[ 80.500031] [<ffffffff83d90898>] tracesys+0xe1/0xe6
The code is:
for (i = 0; i < nsems; i++) {
INIT_LIST_HEAD(&sma->sem_base[i].sem_pending);
spin_lock_init(&sma->sem_base[i].lock);
spin_lock(&sma->sem_base[i].lock); <---- here
}
Thanks,
Sasha
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