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SubjectRe: lockdep splat in CPU hotplug
On Wed, 22 Oct 2014 11:53:49 +0200 (CEST)
Jiri Kosina <jkosina@suse.cz> wrote:


> Still, the lockdep stacktrace is bogus and didn't really help
> understanding this. Any idea why it's wrong?

Could possibly be from a tail call?

>
> > ======================================================
> > [ INFO: possible circular locking dependency detected ]
> > 3.18.0-rc1-00069-gc2661b8 #1 Not tainted
> > -------------------------------------------------------
> > do_s2disk/2367 is trying to acquire lock:
> > (cpuidle_lock){+.+.+.}, at: [<ffffffff814916c2>] cpuidle_pause_and_lock+0x12/0x20
> >
> > but task is already holding lock:
> > (cpu_hotplug.lock#2){+.+.+.}, at: [<ffffffff810522ea>] cpu_hotplug_begin+0x4a/0x80
> >
> > which lock already depends on the new lock.
> >
> > the existing dependency chain (in reverse order) is:
> >
> > -> #1 (cpu_hotplug.lock#2){+.+.+.}:
> > [<ffffffff81099fac>] lock_acquire+0xac/0x130
> > [<ffffffff815b9f2c>] mutex_lock_nested+0x5c/0x3b0
> > [<ffffffff81491892>] cpuidle_pause+0x12/0x30

Where exactly does that address point to?

-- Steve

> > [<ffffffff81402314>] dpm_suspend_noirq+0x44/0x340
> > [<ffffffff81402958>] dpm_suspend_end+0x38/0x80
> > [<ffffffff810a07bd>] hibernation_snapshot+0xcd/0x370
> > [<ffffffff810a1248>] hibernate+0x168/0x210
> > [<ffffffff8109e9b4>] state_store+0xe4/0xf0
> > [<ffffffff813003ef>] kobj_attr_store+0xf/0x20
> > [<ffffffff8121e9a3>] sysfs_kf_write+0x43/0x60
> > [<ffffffff8121e287>] kernfs_fop_write+0xe7/0x170
> > [<ffffffff811a7342>] vfs_write+0xb2/0x1f0
> > [<ffffffff811a7da4>] SyS_write+0x44/0xb0
> > [<ffffffff815be856>] system_call_fastpath+0x16/0x1b
> >
> > -> #0 (cpuidle_lock){+.+.+.}:
> > [<ffffffff81099433>] __lock_acquire+0x1a03/0x1e30
> > [<ffffffff81099fac>] lock_acquire+0xac/0x130
> > [<ffffffff815b9f2c>] mutex_lock_nested+0x5c/0x3b0
> > [<ffffffff814916c2>] cpuidle_pause_and_lock+0x12/0x20
> > [<ffffffffc02e184c>] acpi_processor_hotplug+0x45/0x8a [processor]
> > [<ffffffffc02df25a>] acpi_cpu_soft_notify+0xad/0xe3 [processor]
> > [<ffffffff81071393>] notifier_call_chain+0x53/0xa0
> > [<ffffffff810713e9>] __raw_notifier_call_chain+0x9/0x10
> > [<ffffffff810521ce>] cpu_notify+0x1e/0x40
> > [<ffffffff810524a8>] _cpu_up+0x148/0x160
> > [<ffffffff815a7b99>] enable_nonboot_cpus+0xc9/0x1d0
> > [<ffffffff810a0955>] hibernation_snapshot+0x265/0x370
> > [<ffffffff810a1248>] hibernate+0x168/0x210
> > [<ffffffff8109e9b4>] state_store+0xe4/0xf0
> > [<ffffffff813003ef>] kobj_attr_store+0xf/0x20
> > [<ffffffff8121e9a3>] sysfs_kf_write+0x43/0x60
> > [<ffffffff8121e287>] kernfs_fop_write+0xe7/0x170
> > [<ffffffff811a7342>] vfs_write+0xb2/0x1f0
> > [<ffffffff811a7da4>] SyS_write+0x44/0xb0
> > [<ffffffff815be856>] system_call_fastpath+0x16/0x1b
> >


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