From dbe33fc9ad0cd965afe71cd6fca9539afd704e38 Mon Sep 17 00:00:00 2001 From: Sebastian Ott Date: Tue, 3 Jun 2014 15:03:09 +0200 Subject: [PATCH] s390/cio: silence lockdep warning On systems where a ccw based console device is used a lockdep false alarm could be triggered when a device driver calls printk while holding a subchannels lock (e.g. in it's irq handler). Since this is valid behavior fix this by introducing a separate lock class for the console subchannels lock. The lockdep warning was revealed by "printk: enable interrupts before calling console_trylock_for_printk()" which changed console_unlock() to be called with lockdep enabled. [ INFO: possible recursive locking detected ] 3.15.0-rc5-next-20140520 #1 Not tainted --------------------------------------------- ccwgroup/2239 is trying to acquire lock: (&(sch->lock)->rlock){-.-...}, at: [<0000000000642a52>] raw3215_write+0x52/0x200 but task is already holding lock: (&(sch->lock)->rlock){-.-...}, at: [<00000000005fd160>] do_cio_interrupt+0x60/0x108 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&(sch->lock)->rlock); lock(&(sch->lock)->rlock); *** DEADLOCK *** May be due to missing lock nesting notation 8 locks held by ccwgroup/2239: stack backtrace: CPU: 3 PID: 2239 Comm: ccwgroup Not tainted 3.15.0-rc5-next-20140520 #1 0000000036fab518 0000000036fab528 0000000000000002 0000000000000000 0000000036fab5b8 0000000036fab530 0000000036fab530 00000000001116e8 0000000000000000 0000000000986ec4 00000000009701b6 000000000000000b 0000000036fab578 0000000036fab518 0000000000000000 0000000000000000 0000000000000000 00000000001116e8 0000000036fab518 0000000036fab578 Call Trace: ([<0000000000111626>] show_trace+0x14e/0x158) [<000000000011169a>] show_stack+0x6a/0xe8 [<00000000007c6e72>] dump_stack+0x82/0xb0 [<00000000001a95f2>] validate_chain.isra.37+0xa4a/0xbb0 [<00000000001acaca>] __lock_acquire+0x4da/0xcd0 [<00000000001ada1a>] lock_acquire+0xba/0x218 [<00000000007cd634>] _raw_spin_lock_irqsave+0x6c/0xb8 [<0000000000642a52>] raw3215_write+0x52/0x200 [<0000000000643d16>] con3215_write+0x76/0xf8 [<00000000001bd87a>] call_console_drivers.constprop.25+0xfa/0x210 [<00000000001be0b0>] console_unlock+0x3e0/0x4e8 [<00000000001be450>] vprintk_emit+0x298/0x6e0 [<00000000005aa210>] dev_vprintk_emit+0xe0/0x1a8 [<00000000005aa320>] dev_printk_emit+0x48/0x50 [<00000000005aa390>] __dev_printk+0x68/0xb0 [<00000000005aa7c2>] _dev_info+0x62/0x70 [<0000000000657bf0>] qeth_l2_send_setmac_cb+0xd0/0x190 [<0000000000651a1e>] qeth_send_control_data_cb+0x3a6/0x6a8 [<0000000000655546>] qeth_irq+0x1a6/0xac0 [<000000000060a0ac>] ccw_device_call_handler+0xa4/0xc0 [<0000000000608b62>] ccw_device_irq+0x5a/0x190 [<00000000005fd1ca>] do_cio_interrupt+0xca/0x108 [<00000000001c0a2e>] handle_irq_event_percpu+0x5e/0x378 [<00000000001c46fc>] handle_percpu_irq+0x6c/0x98 [<00000000001c0066>] generic_handle_irq+0x46/0x68 [<000000000010b5b6>] do_IRQ+0x5e/0x88 [<00000000007cf304>] io_call+0x6/0x20 [<000000000064c63a>] qeth_send_control_data+0x322/0x570 ([<000000000064c50e>] qeth_send_control_data+0x1f6/0x570) [<0000000000651db2>] qeth_send_ipa_cmd+0x92/0x120 [<000000000065b310>] __qeth_l2_set_online+0x170/0xaa8 [<000000000060ebb6>] ccwgroup_set_online+0x56/0x90 [<000000000060ef96>] ccwgroup_online_store+0xd6/0xe0 [<000000000033d11a>] kernfs_fop_write+0x10a/0x188 [<00000000002bbd00>] vfs_write+0x98/0x1c0 [<00000000002bc8a0>] SyS_write+0x60/0xd0 [<00000000007cee3a>] sysc_nr_ok+0x22/0x28 [<000003fffd0c3f28>] 0x3fffd0c3f28 Reported-by: Heiko Carstens Signed-off-by: Sebastian Ott Signed-off-by: Martin Schwidefsky --- drivers/s390/cio/cio.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/s390/cio/cio.c b/drivers/s390/cio/cio.c index 77f9c92df4b9..2905d8b0ec95 100644 --- a/drivers/s390/cio/cio.c +++ b/drivers/s390/cio/cio.c @@ -602,6 +602,7 @@ void __init init_cio_interrupts(void) #ifdef CONFIG_CCW_CONSOLE static struct subchannel *console_sch; +static struct lock_class_key console_sch_key; /* * Use cio_tsch to update the subchannel status and call the interrupt handler @@ -686,6 +687,7 @@ struct subchannel *cio_probe_console(void) if (IS_ERR(sch)) return sch; + lockdep_set_class(sch->lock, &console_sch_key); isc_register(CONSOLE_ISC); sch->config.isc = CONSOLE_ISC; sch->config.intparm = (u32)(addr_t)sch; -- GitLab