On 06/30/2017 04:00 PM, Thomas Gleixner wrote: > On Fri, 30 Jun 2017, Andrey Ryabinin wrote: >> On 06/30/2017 01:15 PM, Thomas Gleixner wrote: >>> On Fri, 30 Jun 2017, Michal Hocko wrote: >>>> So I like this simplification a lot! Even if we can get rid of the >>>> stop_machine eventually this patch would be an improvement. A short >>>> comment on why the per-cpu semaphore over the regular one is better >>>> would be nice. >>> >>> Yes, will add one. >>> >>> The main point is that the current locking construct is evading lockdep due >>> to the ability to support recursive locking, which I did not observe so >>> far. >>> >> >> Like this? > > Cute..... > >> [ 131.023034] Call Trace: >> [ 131.023034] dump_stack+0x85/0xc7 >> [ 131.023034] __lock_acquire+0x1747/0x17a0 >> [ 131.023034] ? lru_add_drain_all+0x3d/0x190 >> [ 131.023034] ? __mutex_lock+0x218/0x940 >> [ 131.023034] ? trace_hardirqs_on+0xd/0x10 >> [ 131.023034] lock_acquire+0x103/0x200 >> [ 131.023034] ? lock_acquire+0x103/0x200 >> [ 131.023034] ? lru_add_drain_all+0x42/0x190 >> [ 131.023034] cpus_read_lock+0x3d/0x80 >> [ 131.023034] ? lru_add_drain_all+0x42/0x190 >> [ 131.023034] lru_add_drain_all+0x42/0x190 >> [ 131.023034] __offline_pages.constprop.25+0x5de/0x870 >> [ 131.023034] offline_pages+0xc/0x10 >> [ 131.023034] memory_subsys_offline+0x43/0x70 >> [ 131.023034] device_offline+0x83/0xb0 >> [ 131.023034] store_mem_state+0xdb/0xe0 >> [ 131.023034] dev_attr_store+0x13/0x20 >> [ 131.023034] sysfs_kf_write+0x40/0x50 >> [ 131.023034] kernfs_fop_write+0x130/0x1b0 >> [ 131.023034] __vfs_write+0x23/0x130 >> [ 131.023034] ? rcu_read_lock_sched_held+0x6d/0x80 >> [ 131.023034] ? rcu_sync_lockdep_assert+0x2a/0x50 >> [ 131.023034] ? __sb_start_write+0xd4/0x1c0 >> [ 131.023034] ? vfs_write+0x1a8/0x1d0 >> [ 131.023034] vfs_write+0xc8/0x1d0 >> [ 131.023034] SyS_write+0x44/0xa0 > > Why didn't trigger that here? Bah, I should have become suspicious due to > not seeing a splat .... > > The patch below should cure that. > FWIW, it works for me. > Thanks, > > tglx > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
