[PATCH] timer: Fix lock inversion between hrtimer_bases.lock and scheduler locks

Jan Kara
2014-10-10T14:24:11Z

clockevents_increase_min_delta() calls printk() from under
hrtimer_bases.lock. That causes lock inversion on scheduler locks because
printk() can call into the scheduler. Lockdep puts it as:

======================================================
[ INFO: possible circular locking dependency detected ]
3.15.0-rc8-06195-g939f04b #2 Not tainted
-------------------------------------------------------
trinity-main/74 is trying to acquire lock:
(&port_lock_key){-.....}, at: [<811c60be>] serial8250_console_write+0x8c/0x10c

but task is already holding lock:
(hrtimer_bases.lock){-.-...}, at: [<8103caeb>] hrtimer_try_to_cancel+0x13/0x66

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #5 (hrtimer_bases.lock){-.-...}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<8103c918>] __hrtimer_start_range_ns+0x1c/0x197
[<8107ec20>] perf_swevent_start_hrtimer.part.41+0x7a/0x85
[<81080792>] task_clock_event_start+0x3a/0x3f
[<810807a4>] task_clock_event_add+0xd/0x14
[<8108259a>] event_sched_in+0xb6/0x17a
[<810826a2>] group_sched_in+0x44/0x122
[<81082885>] ctx_sched_in.isra.67+0x105/0x11f
[<810828e6>] perf_event_sched_in.isra.70+0x47/0x4b
[<81082bf6>] __perf_install_in_context+0x8b/0xa3
[<8107eb8e>] remote_function+0x12/0x2a
[<8105f5af>] smp_call_function_single+0x2d/0x53
[<8107e17d>] task_function_call+0x30/0x36
[<8107fb82>] perf_install_in_context+0x87/0xbb
[<810852c9>] SYSC_perf_event_open+0x5c6/0x701
[<810856f9>] SyS_perf_event_open+0x17/0x19
[<8142f8ee>] syscall_call+0x7/0xb

-> #4 (&ctx->lock){......}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f04c>] _raw_spin_lock+0x21/0x30
[<81081df3>] __perf_event_task_sched_out+0x1dc/0x34f
[<8142cacc>] __schedule+0x4c6/0x4cb
[<8142cae0>] schedule+0xf/0x11
[<8142f9a6>] work_resched+0x5/0x30

-> #3 (&rq->lock){-.-.-.}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f04c>] _raw_spin_lock+0x21/0x30
[<81040873>] __task_rq_lock+0x33/0x3a
[<8104184c>] wake_up_new_task+0x25/0xc2
[<8102474b>] do_fork+0x15c/0x2a0
[<810248a9>] kernel_thread+0x1a/0x1f
[<814232a2>] rest_init+0x1a/0x10e
[<817af949>] start_kernel+0x303/0x308
[<817af2ab>] i386_start_kernel+0x79/0x7d

-> #2 (&p->pi_lock){-.-...}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<810413dd>] try_to_wake_up+0x1d/0xd6
[<810414cd>] default_wake_function+0xb/0xd
[<810461f3>] __wake_up_common+0x39/0x59
[<81046346>] __wake_up+0x29/0x3b
[<811b8733>] tty_wakeup+0x49/0x51
[<811c3568>] uart_write_wakeup+0x17/0x19
[<811c5dc1>] serial8250_tx_chars+0xbc/0xfb
[<811c5f28>] serial8250_handle_irq+0x54/0x6a
[<811c5f57>] serial8250_default_handle_irq+0x19/0x1c
[<811c56d8>] serial8250_interrupt+0x38/0x9e
[<810510e7>] handle_irq_event_percpu+0x5f/0x1e2
[<81051296>] handle_irq_event+0x2c/0x43
[<81052cee>] handle_level_irq+0x57/0x80
[<81002a72>] handle_irq+0x46/0x5c
[<810027df>] do_IRQ+0x32/0x89
[<8143036e>] common_interrupt+0x2e/0x33
[<8142f23c>] _raw_spin_unlock_irqrestore+0x3f/0x49
[<811c25a4>] uart_start+0x2d/0x32
[<811c2c04>] uart_write+0xc7/0xd6
[<811bc6f6>] n_tty_write+0xb8/0x35e
[<811b9beb>] tty_write+0x163/0x1e4
[<811b9cd9>] redirected_tty_write+0x6d/0x75
[<810b6ed6>] vfs_write+0x75/0xb0
[<810b7265>] SyS_write+0x44/0x77
[<8142f8ee>] syscall_call+0x7/0xb

-> #1 (&tty->write_wait){-.....}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<81046332>] __wake_up+0x15/0x3b
[<811b8733>] tty_wakeup+0x49/0x51
[<811c3568>] uart_write_wakeup+0x17/0x19
[<811c5dc1>] serial8250_tx_chars+0xbc/0xfb
[<811c5f28>] serial8250_handle_irq+0x54/0x6a
[<811c5f57>] serial8250_default_handle_irq+0x19/0x1c
[<811c56d8>] serial8250_interrupt+0x38/0x9e
[<810510e7>] handle_irq_event_percpu+0x5f/0x1e2
[<81051296>] handle_irq_event+0x2c/0x43
[<81052cee>] handle_level_irq+0x57/0x80
[<81002a72>] handle_irq+0x46/0x5c
[<810027df>] do_IRQ+0x32/0x89
[<8143036e>] common_interrupt+0x2e/0x33
[<8142f23c>] _raw_spin_unlock_irqrestore+0x3f/0x49
[<811c25a4>] uart_start+0x2d/0x32
[<811c2c04>] uart_write+0xc7/0xd6
[<811bc6f6>] n_tty_write+0xb8/0x35e
[<811b9beb>] tty_write+0x163/0x1e4
[<811b9cd9>] redirected_tty_write+0x6d/0x75
[<810b6ed6>] vfs_write+0x75/0xb0
[<810b7265>] SyS_write+0x44/0x77
[<8142f8ee>] syscall_call+0x7/0xb

-> #0 (&port_lock_key){-.....}:
[<8104a62d>] __lock_acquire+0x9ea/0xc6d
[<8104a942>] lock_acquire+0x92/0x101
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<811c60be>] serial8250_console_write+0x8c/0x10c
[<8104e402>] call_console_drivers.constprop.31+0x87/0x118
[<8104f5d5>] console_unlock+0x1d7/0x398
[<8104fb70>] vprintk_emit+0x3da/0x3e4
[<81425f76>] printk+0x17/0x19
[<8105bfa0>] clockevents_program_min_delta+0x104/0x116
[<8105c548>] clockevents_program_event+0xe7/0xf3
[<8105cc1c>] tick_program_event+0x1e/0x23
[<8103c43c>] hrtimer_force_reprogram+0x88/0x8f
[<8103c49e>] __remove_hrtimer+0x5b/0x79
[<8103cb21>] hrtimer_try_to_cancel+0x49/0x66
[<8103cb4b>] hrtimer_cancel+0xd/0x18
[<8107f102>] perf_swevent_cancel_hrtimer.part.60+0x2b/0x30
[<81080705>] task_clock_event_stop+0x20/0x64
[<81080756>] task_clock_event_del+0xd/0xf
[<81081350>] event_sched_out+0xab/0x11e
[<810813e0>] group_sched_out+0x1d/0x66
[<81081682>] ctx_sched_out+0xaf/0xbf
[<81081e04>] __perf_event_task_sched_out+0x1ed/0x34f
[<8142cacc>] __schedule+0x4c6/0x4cb
[<8142cae0>] schedule+0xf/0x11
[<8142f9a6>] work_resched+0x5/0x30

other info that might help us debug this:

Chain exists of:
&port_lock_key --> &ctx->lock --> hrtimer_bases.lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(hrtimer_bases.lock);
lock(&ctx->lock);
lock(hrtimer_bases.lock);
lock(&port_lock_key);

*** DEADLOCK ***

4 locks held by trinity-main/74:
#0: (&rq->lock){-.-.-.}, at: [<8142c6f3>] __schedule+0xed/0x4cb
#1: (&ctx->lock){......}, at: [<81081df3>] __perf_event_task_sched_out+0x1dc/0x34f
#2: (hrtimer_bases.lock){-.-...}, at: [<8103caeb>] hrtimer_try_to_cancel+0x13/0x66
#3: (console_lock){+.+...}, at: [<8104fb5d>] vprintk_emit+0x3c7/0x3e4

stack backtrace:
CPU: 0 PID: 74 Comm: trinity-main Not tainted 3.15.0-rc8-06195-g939f04b #2
00000000 81c3a310 8b995c14 81426f69 8b995c44 81425a99 8161f671 8161f570
8161f538 8161f559 8161f538 8b995c78 8b142bb0 00000004 8b142fdc 8b142bb0
8b995ca8 8104a62d 8b142fac 000016f2 81c3a310 00000001 00000001 00000003
Call Trace:
[<81426f69>] dump_stack+0x16/0x18
[<81425a99>] print_circular_bug+0x18f/0x19c
[<8104a62d>] __lock_acquire+0x9ea/0xc6d
[<8104a942>] lock_acquire+0x92/0x101
[<811c60be>] ? serial8250_console_write+0x8c/0x10c
[<811c6032>] ? wait_for_xmitr+0x76/0x76
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<811c60be>] ? serial8250_console_write+0x8c/0x10c
[<811c60be>] serial8250_console_write+0x8c/0x10c
[<8104af87>] ? lock_release+0x191/0x223
[<811c6032>] ? wait_for_xmitr+0x76/0x76
[<8104e402>] call_console_drivers.constprop.31+0x87/0x118
[<8104f5d5>] console_unlock+0x1d7/0x398
[<8104fb70>] vprintk_emit+0x3da/0x3e4
[<81425f76>] printk+0x17/0x19
[<8105bfa0>] clockevents_program_min_delta+0x104/0x116
[<8105cc1c>] tick_program_event+0x1e/0x23
[<8103c43c>] hrtimer_force_reprogram+0x88/0x8f
[<8103c49e>] __remove_hrtimer+0x5b/0x79
[<8103cb21>] hrtimer_try_to_cancel+0x49/0x66
[<8103cb4b>] hrtimer_cancel+0xd/0x18
[<8107f102>] perf_swevent_cancel_hrtimer.part.60+0x2b/0x30
[<81080705>] task_clock_event_stop+0x20/0x64
[<81080756>] task_clock_event_del+0xd/0xf
[<81081350>] event_sched_out+0xab/0x11e
[<810813e0>] group_sched_out+0x1d/0x66
[<81081682>] ctx_sched_out+0xaf/0xbf
[<81081e04>] __perf_event_task_sched_out+0x1ed/0x34f
[<8104416d>] ? __dequeue_entity+0x23/0x27
[<81044505>] ? pick_next_task_fair+0xb1/0x120
[<8142cacc>] __schedule+0x4c6/0x4cb
[<81047574>] ? trace_hardirqs_off_caller+0xd7/0x108
[<810475b0>] ? trace_hardirqs_off+0xb/0xd
[<81056346>] ? rcu_irq_exit+0x64/0x77

Fix the problem by using printk_deferred() which does not call into the
scheduler.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
---
kernel/time/clockevents.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index ad362c260ef4..9c94c19f1305 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -146,7 +146,8 @@ static int clockevents_increase_min_delta(struct clock_event_device *dev)
{
/* Nothing to do if we already reached the limit */
if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
- printk(KERN_WARNING "CE: Reprogramming failure. Giving up\n");
+ printk_deferred(KERN_WARNING
+ "CE: Reprogramming failure. Giving up\n");
dev->next_event.tv64 = KTIME_MAX;
return -ETIME;
}
@@ -159,9 +160,10 @@ static int clockevents_increase_min_delta(struct clock_event_device *dev)
if (dev->min_delta_ns > MIN_DELTA_LIMIT)
dev->min_delta_ns = MIN_DELTA_LIMIT;

- printk(KERN_WARNING "CE: %s increased min_delta_ns to %llu nsec\n",
- dev->name ? dev->name : "?",
- (unsigned long long) dev->min_delta_ns);
+ printk_deferred(KERN_WARNING
+ "CE: %s increased min_delta_ns to %llu nsec\n",
+ dev->name ? dev->name : "?",
+ (unsigned long long) dev->min_delta_ns);
return 0;