linux-kernel - Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the anon

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Date:	Thu, 8 Apr 2010 07:47:08 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan.kim@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>,
	sgunderson@...foot.com, hannes@...xchg.org
Subject: Re: [PATCH -v2] rmap: make anon_vma_prepare link in all the
 anon_vmas of a mergeable VMA

From: Linus Torvalds <torvalds@...ux-foundation.org>
Date: Wed, Apr 07, 2010 at 07:33:01PM -0700

> Anyway, I think it might be interesting to test my anon_vma_prepare() 
> locking change patch together with Rik's _first_ version of his "fix 
> anon_vma_prepare" thing (the one without the spinlock). They should apply 
> independently of each other, and maybe it all even works together.

There are still issues: vma_adjust() grabs mapping->i_mmap_lock for file
mappings while we might sleep in anon_vma_prepare():

[    9.386929] BUG: sleeping function called from invalid context at mm/rmap.c:119
[    9.387188] in_atomic(): 1, irqs_disabled(): 0, pid: 1068, name: modprobe
[    9.387343] 3 locks held by modprobe/1068:
[    9.387524]  #0:  (&p->cred_guard_mutex){+.+.+.}, at: [<ffffffff810d97fc>] prepare_bprm_creds+0x29/0x5a
[    9.387959]  #1:  (&mm->mmap_sem){++++++}, at: [<ffffffff81110ee2>] elf_map+0x70/0x190
[    9.388416]  #2:  (&(&inode->i_data.i_mmap_lock)->rlock){+.+...}, at: [<ffffffff810bcbdf>] vma_adjust+0x190
/0x3ca
[    9.388848] Pid: 1068, comm: modprobe Not tainted 2.6.34-rc3-00290-ge4b2849 #6
[    9.389102] Call Trace:
[    9.389256]  [<ffffffff810630f6>] ? __debug_show_held_locks+0x22/0x24
[    9.389418]  [<ffffffff8102c288>] __might_sleep+0x117/0x11b
[    9.389570]  [<ffffffff810c0f2e>] anon_vma_prepare+0x30/0x132
[    9.389722]  [<ffffffff810bcd95>] vma_adjust+0x346/0x3ca
[    9.389874]  [<ffffffff810bcf68>] __split_vma+0x14f/0x1b9
[    9.390027]  [<ffffffff810bd143>] do_munmap+0x171/0x315
[    9.390181]  [<ffffffff81110ee2>] ? elf_map+0x70/0x190
[    9.390335]  [<ffffffff81110f9d>] elf_map+0x12b/0x190
[    9.390493]  [<ffffffff81111b35>] load_elf_binary+0xb33/0x170e
[    9.390645]  [<ffffffff8102d529>] ? sub_preempt_count+0xa3/0xb6
[    9.390800]  [<ffffffff810d945a>] search_binary_handler+0x166/0x30e
[    9.390952]  [<ffffffff810d92ab>] ? copy_strings+0x1d4/0x1e5
[    9.391111]  [<ffffffff81111002>] ? load_elf_binary+0x0/0x170e
[    9.391265]  [<ffffffff810dadff>] do_execve+0x1fc/0x2f5
[    9.391424]  [<ffffffff8100a379>] sys_execve+0x43/0x61
[    9.391576]  [<ffffffff810025fa>] stub_execve+0x6a/0xc0


-- 
Regards/Gruss,
Boris.
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