On Tue, 2 Feb 2016, Dmitry Vyukov wrote:
> Hello,
>
> If the following program run in a parallel loop, eventually it leaves
> hanged uninterruptable tasks on mmap_sem.
>
> [ 4074.740298] sysrq: SysRq : Show Locks Held
> [ 4074.740780] Showing all locks held in the system:
> ...
> [ 4074.762133] 1 lock held by a.out/1276:
> [ 4074.762427] #0: (&mm->mmap_sem){++++++}, at: [<ffffffff816df89c>]
> __mm_populate+0x25c/0x350
> [ 4074.763149] 1 lock held by a.out/1147:
> [ 4074.763438] #0: (&mm->mmap_sem){++++++}, at: [<ffffffff816b3bbc>]
> vm_mmap_pgoff+0x12c/0x1b0
> [ 4074.764164] 1 lock held by a.out/1284:
> [ 4074.764447] #0: (&mm->mmap_sem){++++++}, at: [<ffffffff816df89c>]
> __mm_populate+0x25c/0x350
> [ 4074.765287]
I've now tried to reproduce this on 4.5-rc1 (with the lock_fdc() fix
applied), and I am not seeing any stuck tasks so far.
Could you please provide more details about the reproduction scenario?
Namely, how many parallel invocations are you typically running (and how
many cores does the system in question have), and what is the typical time
that you need for the problem to appear?
Thanks,
--
Jiri Kosina
SUSE Labs
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