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Message-ID: <20140801153716.GB7525@quack.suse.cz>
Date: Fri, 1 Aug 2014 17:37:16 +0200
From: Jan Kara <jack@...e.cz>
To: Fengguang Wu <fengguang.wu@...el.com>
Cc: Jan Kara <jack@...e.cz>, Jet Chen <jet.chen@...el.com>,
Su Tao <tao.su@...el.com>, Yuanhan Liu <yuanhan.liu@...el.com>,
LKP <lkp@...org>, linux-kernel@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [printk] INFO: possible circular locking dependency detected
Hello,
On Fri 01-08-14 22:37:54, Wu Fengguang wrote:
> On Fri, Aug 01, 2014 at 12:34:51PM +0200, Jan Kara wrote:
> > Hello,
> >
> > On Fri 01-08-14 09:26:38, Wu Fengguang wrote:
> > > git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > commit 939f04bec1a4ef6ba4370b0f34b01decc844b1b1
> > > Author: Jan Kara <jack@...e.cz>
> > > AuthorDate: Wed Jun 4 16:11:37 2014 -0700
> > > Commit: Linus Torvalds <torvalds@...ux-foundation.org>
> > > CommitDate: Wed Jun 4 16:54:17 2014 -0700
> > >
> > > printk: enable interrupts before calling console_trylock_for_printk()
> > >
> > > We need interrupts disabled when calling console_trylock_for_printk()
> > > only so that cpu id we pass to can_use_console() remains valid (for
> > > other things console_sem provides all the exclusion we need and
> > > deadlocks on console_sem due to interrupts are impossible because we use
> > > down_trylock()). However if we are rescheduled, we are guaranteed to
> > > run on an online cpu so we can easily just get the cpu id in
> > > can_use_console().
> > >
> > > We can lose a bit of performance when we enable interrupts in
> > > vprintk_emit() and then disable them again in console_unlock() but OTOH
> > > it can somewhat reduce interrupt latency caused by console_unlock()
> > > especially since later in the patch series we will want to spin on
> > > console_sem in console_trylock_for_printk().
> > >
> > > Signed-off-by: Jan Kara <jack@...e.cz>
> > > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> > > Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > Thanks for report! Two notes here:
> > 1) This commit has been reverted from upstream already because machines
> > with lockdep enabled were unable to boot in some cases (lockdep decided
> > to report problem and hung the machine while doing it).
> > 2) This patch just makes the problem visible.
> >
> > In this particular case I think the problem is in
> > clockevents_increase_min_delta(). It is calling printk() from under
> > hrtimer_bases.lock and that is causing lock inversion with some scheduler
> > locks.
> >
> > The attached patch should fix the problem. Can you please test it (but you
> > cannot use latest Linus' kernel as that has
> > 939f04bec1a4ef6ba4370b0f34b01decc844b1b1 reverted)?
>
> I applied it immediately immediately before Linus reverting that
> commit. :)
>
> And it does the work, the circular dependency warning disappeared:
>
> +----------------------------------------------------+------------+------------+
> | | e84f1ab33c | 957267fe81 |
> +----------------------------------------------------+------------+------------+
> | boot_successes | 175 | 256 |
> | boot_failures | 25 | 44 |
> | INFO:possible_circular_locking_dependency_detected | 4 | |
> | backtrace:SYSC_perf_event_open | 4 | |
> | backtrace:SyS_perf_event_open | 4 | |
> | backtrace:do_fork | 4 | |
> | backtrace:vfs_write | 4 | |
> | backtrace:SyS_write | 4 | |
> | BUG:kernel_boot_hang | 21 | 44 |
> | backtrace:event_create_dir | 1 | |
> | backtrace:event_trace_init | 1 | |
> | backtrace:kernel_init_freeable | 1 | |
> +----------------------------------------------------+------------+------------+
>
> Tested-by: Fengguang Wu <fengguang.wu@...el.com>
Thanks! Thomas has already put the patch into tip tree so I'm not sure
whether he can still add a tag or not...
Honza
> > > +----------------------------------------------------+------------+------------+------------+
> > > | | bd8d7cf5b8 | 939f04bec1 | fb3ec67942 |
> > > +----------------------------------------------------+------------+------------+------------+
> > > | boot_successes | 1159 | 280 | 41 |
> > > | boot_failures | 41 | 20 | 5 |
> > > | BUG:kernel_boot_hang | 41 | 13 | 3 |
> > > | INFO:possible_circular_locking_dependency_detected | 0 | 7 | 2 |
> > > | backtrace:do_fork | 0 | 7 | 2 |
> > > | backtrace:vfs_write | 0 | 7 | 2 |
> > > | backtrace:SyS_write | 0 | 7 | 2 |
> > > | backtrace:event_create_dir | 0 | 2 | 1 |
> > > | backtrace:event_trace_init | 0 | 2 | 1 |
> > > | backtrace:kernel_init_freeable | 0 | 3 | 1 |
> > > | backtrace:SYSC_perf_event_open | 0 | 7 | 2 |
> > > | backtrace:SyS_perf_event_open | 0 | 7 | 2 |
> > > | backtrace:trace_create_cpu_file | 0 | 1 | |
> > > | backtrace:init_tracer_debugfs | 0 | 1 | |
> > > | backtrace:tracer_init_debugfs | 0 | 1 | |
> > > +----------------------------------------------------+------------+------------+------------+
> > >
> > > [ 29.644027] CE: hpet increased min_delta_ns to 25312 nsec
> > > [ 29.644027]
> > > [ 29.644027] ======================================================
> > > [ 29.644027] [ INFO: possible circular locking dependency detected ]
> > > [ 29.644027] 3.15.0-rc8-06195-g939f04b #2 Not tainted
> > > [ 29.644027] -------------------------------------------------------
> > > [ 29.644027] trinity-main/74 is trying to acquire lock:
> > > [ 29.644027] (&port_lock_key){-.....}, at: [<811c60be>] serial8250_console_write+0x8c/0x10c
> > > [ 29.644027]
> > > [ 29.644027] but task is already holding lock:
> > > [ 29.644027] (hrtimer_bases.lock){-.-...}, at: [<8103caeb>] hrtimer_try_to_cancel+0x13/0x66
> > > [ 29.644027]
> > > [ 29.644027] which lock already depends on the new lock.
> > > [ 29.644027]
> > > [ 29.644027]
> > > [ 29.644027] the existing dependency chain (in reverse order) is:
> > > [ 29.644027]
> > > [ 29.644027] -> #5 (hrtimer_bases.lock){-.-...}:
> > > [ 29.644027] [<8104a942>] lock_acquire+0x92/0x101
> > > [ 29.644027] [<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
> > > [ 29.644027] [<8103c918>] __hrtimer_start_range_ns+0x1c/0x197
> > > [ 29.644027] [<8107ec20>] perf_swevent_start_hrtimer.part.41+0x7a/0x85
> > > [ 29.644027] [<81080792>] task_clock_event_start+0x3a/0x3f
> > > [ 29.644027] [<810807a4>] task_clock_event_add+0xd/0x14
> > > [ 29.644027] [<8108259a>] event_sched_in+0xb6/0x17a
> > > [ 29.644027] [<810826a2>] group_sched_in+0x44/0x122
> > > [ 29.644027] [<81082885>] ctx_sched_in.isra.67+0x105/0x11f
> > > [ 29.644027] [<810828e6>] perf_event_sched_in.isra.70+0x47/0x4b
> > > [ 29.644027] [<81082bf6>] __perf_install_in_context+0x8b/0xa3
> > > [ 29.644027] [<8107eb8e>] remote_function+0x12/0x2a
> > > [ 29.644027] [<8105f5af>] smp_call_function_single+0x2d/0x53
> > > [ 29.644027] [<8107e17d>] task_function_call+0x30/0x36
> > > [ 29.644027] [<8107fb82>] perf_install_in_context+0x87/0xbb
> > > [ 29.644027] [<810852c9>] SYSC_perf_event_open+0x5c6/0x701
> > > [ 29.644027] [<810856f9>] SyS_perf_event_open+0x17/0x19
> > > [ 29.644027] [<8142f8ee>] syscall_call+0x7/0xb
> > > [ 29.644027]
> > > [ 29.644027] -> #4 (&ctx->lock){......}:
> > > [ 29.644027] [<8104a942>] lock_acquire+0x92/0x101
> > > [ 29.644027] [<8142f04c>] _raw_spin_lock+0x21/0x30
> > > [ 29.644027] [<81081df3>] __perf_event_task_sched_out+0x1dc/0x34f
> > > [ 29.644027] [<8142cacc>] __schedule+0x4c6/0x4cb
> > > [ 29.644027] [<8142cae0>] schedule+0xf/0x11
> > > [ 29.644027] [<8142f9a6>] work_resched+0x5/0x30
> > > [ 29.644027]
> > > [ 29.644027] -> #3 (&rq->lock){-.-.-.}:
> > > [ 29.644027] [<8104a942>] lock_acquire+0x92/0x101
> > > [ 29.644027] [<8142f04c>] _raw_spin_lock+0x21/0x30
> > > [ 29.644027] [<81040873>] __task_rq_lock+0x33/0x3a
> > > [ 29.644027] [<8104184c>] wake_up_new_task+0x25/0xc2
> > > [ 29.644027] [<8102474b>] do_fork+0x15c/0x2a0
> > > [ 29.644027] [<810248a9>] kernel_thread+0x1a/0x1f
> > > [ 29.644027] [<814232a2>] rest_init+0x1a/0x10e
> > > [ 29.644027] [<817af949>] start_kernel+0x303/0x308
> > > [ 29.644027] [<817af2ab>] i386_start_kernel+0x79/0x7d
> > > [ 29.644027]
> > > [ 29.644027] -> #2 (&p->pi_lock){-.-...}:
> > > [ 29.644027] [<8104a942>] lock_acquire+0x92/0x101
> > > [ 29.644027] [<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
> > > [ 29.644027] [<810413dd>] try_to_wake_up+0x1d/0xd6
> > > [ 29.644027] [<810414cd>] default_wake_function+0xb/0xd
> > > [ 29.644027] [<810461f3>] __wake_up_common+0x39/0x59
> > > [ 29.644027] [<81046346>] __wake_up+0x29/0x3b
> > > [ 29.644027] [<811b8733>] tty_wakeup+0x49/0x51
> > > [ 29.644027] [<811c3568>] uart_write_wakeup+0x17/0x19
> > > [ 29.644027] [<811c5dc1>] serial8250_tx_chars+0xbc/0xfb
> > > [ 29.644027] [<811c5f28>] serial8250_handle_irq+0x54/0x6a
> > > [ 29.644027] [<811c5f57>] serial8250_default_handle_irq+0x19/0x1c
> > > [ 29.644027] [<811c56d8>] serial8250_interrupt+0x38/0x9e
> > > [ 29.644027] [<810510e7>] handle_irq_event_percpu+0x5f/0x1e2
> > > [ 29.644027] [<81051296>] handle_irq_event+0x2c/0x43
> > > [ 29.644027] [<81052cee>] handle_level_irq+0x57/0x80
> > > [ 29.644027] [<81002a72>] handle_irq+0x46/0x5c
> > > [ 29.644027] [<810027df>] do_IRQ+0x32/0x89
> > > [ 29.644027] [<8143036e>] common_interrupt+0x2e/0x33
> > > [ 29.644027] [<8142f23c>] _raw_spin_unlock_irqrestore+0x3f/0x49
> > > [ 29.644027] [<811c25a4>] uart_start+0x2d/0x32
> > > [ 29.644027] [<811c2c04>] uart_write+0xc7/0xd6
> > > [ 29.644027] [<811bc6f6>] n_tty_write+0xb8/0x35e
> > > [ 29.644027] [<811b9beb>] tty_write+0x163/0x1e4
> > > [ 29.644027] [<811b9cd9>] redirected_tty_write+0x6d/0x75
> > > [ 29.644027] [<810b6ed6>] vfs_write+0x75/0xb0
> > > [ 29.644027] [<810b7265>] SyS_write+0x44/0x77
> > > [ 29.644027] [<8142f8ee>] syscall_call+0x7/0xb
> > > [ 29.644027]
> > > [ 29.644027] -> #1 (&tty->write_wait){-.....}:
> > > [ 29.644027] [<8104a942>] lock_acquire+0x92/0x101
> > > [ 29.644027] [<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
> > > [ 29.644027] [<81046332>] __wake_up+0x15/0x3b
> > > [ 29.644027] [<811b8733>] tty_wakeup+0x49/0x51
> > > [ 29.644027] [<811c3568>] uart_write_wakeup+0x17/0x19
> > > [ 29.644027] [<811c5dc1>] serial8250_tx_chars+0xbc/0xfb
> > > [ 29.644027] [<811c5f28>] serial8250_handle_irq+0x54/0x6a
> > > [ 29.644027] [<811c5f57>] serial8250_default_handle_irq+0x19/0x1c
> > > [ 29.644027] [<811c56d8>] serial8250_interrupt+0x38/0x9e
> > > [ 29.644027] [<810510e7>] handle_irq_event_percpu+0x5f/0x1e2
> > > [ 29.644027] [<81051296>] handle_irq_event+0x2c/0x43
> > > [ 29.644027] [<81052cee>] handle_level_irq+0x57/0x80
> > > [ 29.644027] [<81002a72>] handle_irq+0x46/0x5c
> > > [ 29.644027] [<810027df>] do_IRQ+0x32/0x89
> > > [ 29.644027] [<8143036e>] common_interrupt+0x2e/0x33
> > > [ 29.644027] [<8142f23c>] _raw_spin_unlock_irqrestore+0x3f/0x49
> > > [ 29.644027] [<811c25a4>] uart_start+0x2d/0x32
> > > [ 29.644027] [<811c2c04>] uart_write+0xc7/0xd6
> > > [ 29.644027] [<811bc6f6>] n_tty_write+0xb8/0x35e
> > > [ 29.644027] [<811b9beb>] tty_write+0x163/0x1e4
> > > [ 29.644027] [<811b9cd9>] redirected_tty_write+0x6d/0x75
> > > [ 29.644027] [<810b6ed6>] vfs_write+0x75/0xb0
> > > [ 29.644027] [<810b7265>] SyS_write+0x44/0x77
> > > [ 29.644027] [<8142f8ee>] syscall_call+0x7/0xb
> > > [ 29.644027]
> > > [ 29.644027] -> #0 (&port_lock_key){-.....}:
> > > [ 29.644027] [<8104a62d>] __lock_acquire+0x9ea/0xc6d
> > > [ 29.644027] [<8104a942>] lock_acquire+0x92/0x101
> > > [ 29.644027] [<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
> > > [ 29.644027] [<811c60be>] serial8250_console_write+0x8c/0x10c
> > > [ 29.644027] [<8104e402>] call_console_drivers.constprop.31+0x87/0x118
> > > [ 29.644027] [<8104f5d5>] console_unlock+0x1d7/0x398
> > > [ 29.644027] [<8104fb70>] vprintk_emit+0x3da/0x3e4
> > > [ 29.644027] [<81425f76>] printk+0x17/0x19
> > > [ 29.644027] [<8105bfa0>] clockevents_program_min_delta+0x104/0x116
> > > [ 29.644027] [<8105c548>] clockevents_program_event+0xe7/0xf3
> > > [ 29.644027] [<8105cc1c>] tick_program_event+0x1e/0x23
> > > [ 29.644027] [<8103c43c>] hrtimer_force_reprogram+0x88/0x8f
> > > [ 29.644027] [<8103c49e>] __remove_hrtimer+0x5b/0x79
> > > [ 29.644027] [<8103cb21>] hrtimer_try_to_cancel+0x49/0x66
> > > [ 29.644027] [<8103cb4b>] hrtimer_cancel+0xd/0x18
> > > [ 29.644027] [<8107f102>] perf_swevent_cancel_hrtimer.part.60+0x2b/0x30
> > > [ 29.644027] [<81080705>] task_clock_event_stop+0x20/0x64
> > > [ 29.644027] [<81080756>] task_clock_event_del+0xd/0xf
> > > [ 29.644027] [<81081350>] event_sched_out+0xab/0x11e
> > > [ 29.644027] [<810813e0>] group_sched_out+0x1d/0x66
> > > [ 29.644027] [<81081682>] ctx_sched_out+0xaf/0xbf
> > > [ 29.644027] [<81081e04>] __perf_event_task_sched_out+0x1ed/0x34f
> > > [ 29.644027] [<8142cacc>] __schedule+0x4c6/0x4cb
> > > [ 29.644027] [<8142cae0>] schedule+0xf/0x11
> > > [ 29.644027] [<8142f9a6>] work_resched+0x5/0x30
> > > [ 29.644027]
> > > [ 29.644027] other info that might help us debug this:
> > > [ 29.644027]
> > > [ 29.644027] Chain exists of:
> > > [ 29.644027] &port_lock_key --> &ctx->lock --> hrtimer_bases.lock
> > > [ 29.644027]
> > > [ 29.644027] Possible unsafe locking scenario:
> > > [ 29.644027]
> > > [ 29.644027] CPU0 CPU1
> > > [ 29.644027] ---- ----
> > > [ 29.644027] lock(hrtimer_bases.lock);
> > > [ 29.644027] lock(&ctx->lock);
> > > [ 29.644027] lock(hrtimer_bases.lock);
> > > [ 29.644027] lock(&port_lock_key);
> > > [ 29.644027]
> > > [ 29.644027] *** DEADLOCK ***
> > > [ 29.644027]
> > > [ 29.644027] 4 locks held by trinity-main/74:
> > > [ 29.644027] #0: (&rq->lock){-.-.-.}, at: [<8142c6f3>] __schedule+0xed/0x4cb
> > > [ 29.644027] #1: (&ctx->lock){......}, at: [<81081df3>] __perf_event_task_sched_out+0x1dc/0x34f
> > > [ 29.644027] #2: (hrtimer_bases.lock){-.-...}, at: [<8103caeb>] hrtimer_try_to_cancel+0x13/0x66
> > > [ 29.644027] #3: (console_lock){+.+...}, at: [<8104fb5d>] vprintk_emit+0x3c7/0x3e4
> > > [ 29.644027]
> > > [ 29.644027] stack backtrace:
> > > [ 29.644027] CPU: 0 PID: 74 Comm: trinity-main Not tainted 3.15.0-rc8-06195-g939f04b #2
> > > [ 29.644027] 00000000 81c3a310 8b995c14 81426f69 8b995c44 81425a99 8161f671 8161f570
> > > [ 29.644027] 8161f538 8161f559 8161f538 8b995c78 8b142bb0 00000004 8b142fdc 8b142bb0
> > > [ 29.644027] 8b995ca8 8104a62d 8b142fac 000016f2 81c3a310 00000001 00000001 00000003
> > > [ 29.644027] Call Trace:
> > > [ 29.644027] [<81426f69>] dump_stack+0x16/0x18
> > > [ 29.644027] [<81425a99>] print_circular_bug+0x18f/0x19c
> > > [ 29.644027] [<8104a62d>] __lock_acquire+0x9ea/0xc6d
> > > [ 29.644027] [<8104a942>] lock_acquire+0x92/0x101
> > > [ 29.644027] [<811c60be>] ? serial8250_console_write+0x8c/0x10c
> > > [ 29.644027] [<811c6032>] ? wait_for_xmitr+0x76/0x76
> > > [ 29.644027] [<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
> > > [ 29.644027] [<811c60be>] ? serial8250_console_write+0x8c/0x10c
> > > [ 29.644027] [<811c60be>] serial8250_console_write+0x8c/0x10c
> > > [ 29.644027] [<8104af87>] ? lock_release+0x191/0x223
> > > [ 29.644027] [<811c6032>] ? wait_for_xmitr+0x76/0x76
> > > [ 29.644027] [<8104e402>] call_console_drivers.constprop.31+0x87/0x118
> > > [ 29.644027] [<8104f5d5>] console_unlock+0x1d7/0x398
> > > [ 29.644027] [<8104fb70>] vprintk_emit+0x3da/0x3e4
> > > [ 29.644027] [<81425f76>] printk+0x17/0x19
> > > [ 29.644027] [<8105bfa0>] clockevents_program_min_delta+0x104/0x116
> > > [ 29.644027] [<8105c548>] clockevents_program_event+0xe7/0xf3
> > > [ 29.644027] [<8105cc1c>] tick_program_event+0x1e/0x23
> > > [ 29.644027] [<8103c43c>] hrtimer_force_reprogram+0x88/0x8f
> > > [ 29.644027] [<8103c49e>] __remove_hrtimer+0x5b/0x79
> > > [ 29.644027] [<8103cb21>] hrtimer_try_to_cancel+0x49/0x66
> > > [ 29.644027] [<8103cb4b>] hrtimer_cancel+0xd/0x18
> > > [ 29.644027] [<8107f102>] perf_swevent_cancel_hrtimer.part.60+0x2b/0x30
> > > [ 29.644027] [<81080705>] task_clock_event_stop+0x20/0x64
> > > [ 29.644027] [<81080756>] task_clock_event_del+0xd/0xf
> > > [ 29.644027] [<81081350>] event_sched_out+0xab/0x11e
> > > [ 29.644027] [<810813e0>] group_sched_out+0x1d/0x66
> > > [ 29.644027] [<81081682>] ctx_sched_out+0xaf/0xbf
> > > [ 29.644027] [<81081e04>] __perf_event_task_sched_out+0x1ed/0x34f
> > > [ 29.644027] [<8104416d>] ? __dequeue_entity+0x23/0x27
> > > [ 29.644027] [<81044505>] ? pick_next_task_fair+0xb1/0x120
> > > [ 29.644027] [<8142cacc>] __schedule+0x4c6/0x4cb
> > > [ 29.644027] [<81047574>] ? trace_hardirqs_off_caller+0xd7/0x108
> > > [ 29.644027] [<810475b0>] ? trace_hardirqs_off+0xb/0xd
> > > [ 29.644027] [<81056346>] ? rcu_irq_exit+0x64/0x77
> > >
> > > git bisect start 9f6226a762c7ae02f6a23a3d4fc552dafa57ea23 v3.15 --
> > > git bisect bad 71998d1be4ae70e7d320cdd21595c1a02a29c61e # 01:13 79- 5 Merge branch 'x86-irq-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
> > > git bisect bad 9ee4d7a6538308a7681b638d2f35f2a301420355 # 01:24 3- 1 Merge branch 'akpm' (patches from Andrew Morton)
> > > git bisect bad 9894e6d9c020b754dd962960e9f7eac18282f69f # 01:58 128- 5 Merge tag 'fbdev-omap-dt-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tomba/linux
> > > git bisect bad 963649d735c8b6eb0f97e82c54f02426ff3f1f45 # 02:06 48- 3 Merge tag 'for-linus-3.16-merge-window' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs
> > > git bisect bad b20dcab9d4589ef9918a13c888c5493945adfc13 # 02:13 35- 1 Merge tag 'llvmlinux-for-v3.16' of git://git.linuxfoundation.org/llvmlinux/kernel
> > > git bisect bad 3f17ea6dea8ba5668873afa54628a91aaa3fb1c0 # 02:19 58- 4 Merge branch 'next' (accumulated 3.16 merge window patches) into master
> > > git bisect good 49eb7b0750d9483c74e9c14ae6ea1e9d62481c3c # 02:35 300+ 7 Merge tag 'tty-3.16-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty into next
> > > git bisect good 15b588303155b22edd559672905db8e59a44ef9a # 02:51 300+ 0 Merge tag 'fbdev-omap-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tomba/linux into next
> > > git bisect good d09cc3659db494aca4b3bb2393c533fb4946b794 # 03:19 300+ 1 Merge branch 'irq-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip into next
> > > git bisect bad cc07aabc53978ae09a1d539237189f7c9841060a # 03:37 66- 2 Merge tag 'arm64-upstream' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux into next
> > > git bisect bad 8091b895b76f690aa2f6689b6ed602f07525a938 # 04:55 103- 1 fs/ncpfs/getopt.c: replace simple_strtoul by kstrtoul
> > > git bisect good d53aea3d46d64e95da9952887969f7533b9ab25e # 05:59 300+ 19 mm, compaction: return failed migration target pages back to freelist
> > > git bisect good 72d09633c9afa02bea317d65eb8b8a4ce7659a2a # 06:31 300+ 10 mm/zswap: NUMA aware allocation for zswap_dstmem
> > > git bisect bad 0046dd9fed0c9313cbb4fb860324476cd298dc9f # 06:35 42- 1 lib/string.c: use the name "C-string" in comments
> > > git bisect good 0a581694ab7a5bc083d710df8a552a6a055b005f # 06:54 300+ 15 printk: split code for making free space in the log buffer
> > > git bisect bad 939f04bec1a4ef6ba4370b0f34b01decc844b1b1 # 06:58 46- 2 printk: enable interrupts before calling console_trylock_for_printk()
> > > git bisect good 034633ccb24d675850f99bf85c1c5880c831e4b6 # 07:16 300+ 28 printk: return really stored message length
> > > git bisect good 608873cacb9d0d2811586fcc79a38b64eabd6d32 # 07:29 300+ 22 printk: release lockbuf_lock before calling console_trylock_for_printk()
> > > git bisect good bd8d7cf5b8410fe98eba06a9aaa90efe88815d8a # 07:42 300+ 7 printk: fix lockdep instrumentation of console_sem
> > > # first bad commit: [939f04bec1a4ef6ba4370b0f34b01decc844b1b1] printk: enable interrupts before calling console_trylock_for_printk()
> > > git bisect good bd8d7cf5b8410fe98eba06a9aaa90efe88815d8a # 08:21 900+ 41 printk: fix lockdep instrumentation of console_sem
> > > git bisect bad fb3ec67942e92e5713e05b7691b277d0a0c0575d # 08:21 0- 5 KVM: arm64: GICv3: mandate page-aligned GICV region
> > > git bisect good 6f0928036bcbd8dd2ebee9201580da8bcc0a81af # 08:49 900+ 87 Merge tag 'pm+acpi-3.16-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
> > >
> > >
> > > This script may reproduce the error.
> > >
> > > ----------------------------------------------------------------------------
> > > #!/bin/bash
> > >
> > > kernel=$1
> > > initrd=quantal-core-i386.cgz
> > >
> > > wget --no-clobber https://github.com/fengguang/reproduce-kernel-bug/raw/master/initrd/$initrd
> > >
> > > kvm=(
> > > qemu-system-x86_64
> > > -enable-kvm
> > > -cpu Haswell,+smep,+smap
> > > -kernel $kernel
> > > -initrd $initrd
> > > -m 320
> > > -smp 2
> > > -net nic,vlan=1,model=e1000
> > > -net user,vlan=1
> > > -boot order=nc
> > > -no-reboot
> > > -watchdog i6300esb
> > > -rtc base=localtime
> > > -serial stdio
> > > -display none
> > > -monitor null
> > > )
> > >
> > > append=(
> > > hung_task_panic=1
> > > earlyprintk=ttyS0,115200
> > > debug
> > > apic=debug
> > > sysrq_always_enabled
> > > rcupdate.rcu_cpu_stall_timeout=100
> > > panic=10
> > > softlockup_panic=1
> > > nmi_watchdog=panic
> > > prompt_ramdisk=0
> > > console=ttyS0,115200
> > > console=tty0
> > > vga=normal
> > > root=/dev/ram0
> > > rw
> > > drbd.minor_count=8
> > > )
> > >
> > > "${kvm[@]}" --append "${append[*]}"
> > > ----------------------------------------------------------------------------
> >
> > --
> > Jan Kara <jack@...e.cz>
> > SUSE Labs, CR
>
> > >From 3cf8a191b7c48ba10239892efbfe830ab189e93a Mon Sep 17 00:00:00 2001
> > From: Jan Kara <jack@...e.cz>
> > Date: Fri, 1 Aug 2014 12:20:02 +0200
> > Subject: [PATCH] timer: Fix lock inversion between hrtimer_bases.lock and
> > scheduler locks
> >
> > 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@...el.com>
> > Signed-off-by: Jan Kara <jack@...e.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;
> > }
> >
> > --
> > 1.8.1.4
> >
>
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
--
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