On Wed, 24 Oct 2012, Sasha Levin wrote:
> > This should be fixed by 9e7814404b77 ("hold task->mempolicy while
> > numa_maps scans.") in 3.7-rc2, can you reproduce any issues reading
> > /proc/pid/numa_maps on that kernel?
>
> I was actually referring to the warnings Dave Jones saw when fuzzing
> with trinity after the
> original patch was applied.
>
> I still see the following when fuzzing:
>
> [ 338.467156] BUG: sleeping function called from invalid context at
> kernel/mutex.c:269
> [ 338.473719] in_atomic(): 1, irqs_disabled(): 0, pid: 6361, name: trinity-main
> [ 338.481199] 2 locks held by trinity-main/6361:
> [ 338.486629] #0: (&mm->mmap_sem){++++++}, at: [<ffffffff810aa314>]
> __do_page_fault+0x1e4/0x4f0
> [ 338.498783] #1: (&(&mm->page_table_lock)->rlock){+.+...}, at:
> [<ffffffff8122f017>] handle_pte_fault+0x3f7/0x6a0
> [ 338.511409] Pid: 6361, comm: trinity-main Tainted: G W
> 3.7.0-rc2-next-20121024-sasha-00001-gd95ef01-dirty #74
> [ 338.530318] Call Trace:
> [ 338.534088] [<ffffffff8114e393>] __might_sleep+0x1c3/0x1e0
> [ 338.539358] [<ffffffff83ae5209>] mutex_lock_nested+0x29/0x50
> [ 338.545253] [<ffffffff8124fc3e>] mpol_shared_policy_lookup+0x2e/0x90
> [ 338.545258] [<ffffffff81219ebe>] shmem_get_policy+0x2e/0x30
> [ 338.545264] [<ffffffff8124e99a>] get_vma_policy+0x5a/0xa0
> [ 338.545267] [<ffffffff8124fce1>] mpol_misplaced+0x41/0x1d0
> [ 338.545272] [<ffffffff8122f085>] handle_pte_fault+0x465/0x6a0
> [ 338.545278] [<ffffffff81131e04>] ? __rcu_read_unlock+0x44/0xb0
> [ 338.545282] [<ffffffff81230baa>] handle_mm_fault+0x32a/0x360
> [ 338.545286] [<ffffffff810aa5b0>] __do_page_fault+0x480/0x4f0
> [ 338.545293] [<ffffffff8111a706>] ? del_timer+0x26/0x80
> [ 338.545298] [<ffffffff811c7313>] ? rcu_cleanup_after_idle+0x23/0x170
> [ 338.545302] [<ffffffff811ca9a4>] ? rcu_eqs_exit_common+0x64/0x3a0
> [ 338.545305] [<ffffffff811c8c66>] ? rcu_eqs_enter_common+0x7c6/0x970
> [ 338.545309] [<ffffffff811cafdc>] ? rcu_eqs_exit+0x9c/0xb0
> [ 338.545312] [<ffffffff810aa666>] do_page_fault+0x26/0x40
> [ 338.545317] [<ffffffff810a3a40>] do_async_page_fault+0x30/0xa0
> [ 338.545321] [<ffffffff83ae9268>] async_page_fault+0x28/0x30
>
Ok, this looks the same but it's actually a different issue:
mpol_misplaced(), which now only exists in linux-next and not in 3.7-rc2,
calls get_vma_policy() which may take the shared policy mutex. This
happens while holding page_table_lock from do_huge_pmd_numa_page() but
also from do_numa_page() while holding a spinlock on the ptl, which is
coming from the sched/numa branch.
Is there anyway that we can avoid changing the shared policy mutex back
into a spinlock (it was converted in b22d127a39dd ["mempolicy: fix a race
in shared_policy_replace()"])?
Adding Peter, Rik, and Mel to the cc.
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