linux-kernel - [PATCH v2] x86: add might_sleep() to do_page

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Date:	Thu, 29 Jan 2009 16:02:12 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Frank Mehnert <Frank.Mehnert@....COM>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>
Subject: [PATCH v2] x86: add might_sleep() to do_page_fault()


> should go into the 'else' branch i guess? In the down_read() case we 
> already had the check.

True.

---
VirtualBox calls do_page_fault() from an atomic context but runs into a
might_sleep() way pas this point, cure that.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
 arch/x86/mm/fault.c |    6 ++++++
 1 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 67e4df5..bfac289 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -907,6 +907,12 @@ void __kprobes do_page_fault(struct pt_regs *regs, unsigned long error_code)
 			return;
 		}
 		down_read(&mm->mmap_sem);
+	} else {
+		/*
+		 * The above down_read_trylock() might have succeeded in which
+		 * case we'll have missed the might_sleep() from down_read().
+		 */
+		might_sleep();
 	}
 
 	vma = find_vma(mm, address);


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