Messages in this thread |  | | Date | Fri, 25 Aug 2017 16:47:55 +0200 | From | Sebastian Andrzej Siewior <> | Subject | Re: WARNING: possible circular locking dependency detected |
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On 2017-08-25 12:03:04 [+0200], Borislav Petkov wrote: > ====================================================== > WARNING: possible circular locking dependency detected > 4.13.0-rc6+ #1 Not tainted > ------------------------------------------------------
While looking at this, I stumbled upon another one also enabled by "completion annotation" in the TIP:
| ====================================================== | WARNING: possible circular locking dependency detected | 4.13.0-rc6-00758-gd80d4177391f-dirty #112 Not tainted | ------------------------------------------------------ | cpu-off.sh/426 is trying to acquire lock: | ((complete)&st->done){+.+.}, at: [<ffffffff810cb344>] takedown_cpu+0x84/0xf0 | | but task is already holding lock: | (sparse_irq_lock){+.+.}, at: [<ffffffff811220f2>] irq_lock_sparse+0x12/0x20 | | which lock already depends on the new lock. | | the existing dependency chain (in reverse order) is: | | -> #1 (sparse_irq_lock){+.+.}: | __mutex_lock+0x88/0x9a0 | mutex_lock_nested+0x16/0x20 | irq_lock_sparse+0x12/0x20 | irq_affinity_online_cpu+0x13/0xd0 | cpuhp_invoke_callback+0x4a/0x130 | | -> #0 ((complete)&st->done){+.+.}: | check_prev_add+0x351/0x700 | __lock_acquire+0x114a/0x1220 | lock_acquire+0x47/0x70 | wait_for_completion+0x5c/0x180 | takedown_cpu+0x84/0xf0 | cpuhp_invoke_callback+0x4a/0x130 | cpuhp_down_callbacks+0x3d/0x80 … | | other info that might help us debug this: | | Possible unsafe locking scenario: | CPU0 CPU1 | ---- ---- | lock(sparse_irq_lock); | lock((complete)&st->done); | lock(sparse_irq_lock); | lock((complete)&st->done); | | *** DEADLOCK ***
We hold the sparse_irq_lock lock while waiting for the completion in the CPU-down case and in the CPU-up case we acquire the sparse_irq_lock lock while the other CPU is waiting for the completion. This is not an issue if my interpretation of lockdep here is correct.
How do we annotate this?
Sebastian
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