Messages in this thread | | | Subject | Re: rcu: endless stalls | From | Mike Galbraith <> | Date | Wed, 13 Jun 2012 05:35:08 +0200 |
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On Mon, 2012-06-11 at 20:10 +0200, Mike Galbraith wrote: > On Mon, 2012-06-11 at 11:01 -0700, Paul E. McKenney wrote:
> > > 2aa15890 - mm: prevent concurrent unmap_mapping_range() on the same inode > > > > I confess, you lost me on this one. You believe that this commit is > > the cause of the RCU CPU stall warnings? > > 4096 tasks on 4096 CPUs exit (well, try to) simultaneously. > > Call Trace: > __mutex_lock_slowpath+0x94/0x150 > mutex_lock+0x1a/0x40 > unlink_file_vma+0x3f/0xf0 > free_pgtables+0x40/0x100 > exit_mmap+0xb0/0x120 > mmput+0x49/0x120 > exit_mm+0x122/0x160 > do_exit+0x179/0x8d0 > do_group_exit+0x3d/0xb0 > sys_exit_group+0x12/0x20 > > Monster box dies screaming.
That commit landed in stable, box with way too many cores (NR_CPUS=0!!) chokes instantly with loads of spinners. Ok, so zillion CPUs grabbing a mutex in lockstep is a bad idea (_having_ zillion?), but is there pilot error involved in a logjam like this?
-Mike
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