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author | Michael S. Tsirkin <mst@redhat.com> | 2013-05-26 16:32:23 +0200 |
---|---|---|
committer | Ingo Molnar <mingo@kernel.org> | 2013-05-28 09:41:11 +0200 |
commit | 662bbcb2747c2422cf98d3d97619509379eee466 (patch) | |
tree | d733c7257e59bde654d963cce0e26454a134d787 /mm/memory.c | |
parent | mm, sched: Drop voluntary schedule from might_fault() (diff) | |
download | linux-662bbcb2747c2422cf98d3d97619509379eee466.tar.xz linux-662bbcb2747c2422cf98d3d97619509379eee466.zip |
mm, sched: Allow uaccess in atomic with pagefault_disable()
This changes might_fault() so that it does not
trigger a false positive diagnostic for e.g. the following
sequence:
spin_lock_irqsave()
pagefault_disable()
copy_to_user()
pagefault_enable()
spin_unlock_irqrestore()
In particular vhost wants to do this, to call
socket ops from under a lock.
There are 3 cases to consider:
- CONFIG_PROVE_LOCKING - might_fault is non-inline
so it's easy to move the in_atomic test to fix
up the false positive warning.
- CONFIG_DEBUG_ATOMIC_SLEEP - might_fault
is currently inline, but we are calling a
non-inline __might_sleep anyway,
so let's use the non-line version of might_fault
that does the right thing.
- !CONFIG_DEBUG_ATOMIC_SLEEP && !CONFIG_PROVE_LOCKING
__might_sleep is a nop so might_fault is a nop.
Make this explicit.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1369577426-26721-11-git-send-email-mst@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'mm/memory.c')
-rw-r--r-- | mm/memory.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/mm/memory.c b/mm/memory.c index c1f190f51f6f..d7d54a114773 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -4210,7 +4210,7 @@ void print_vma_addr(char *prefix, unsigned long ip) up_read(&mm->mmap_sem); } -#ifdef CONFIG_PROVE_LOCKING +#if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP) void might_fault(void) { /* @@ -4222,14 +4222,17 @@ void might_fault(void) if (segment_eq(get_fs(), KERNEL_DS)) return; - __might_sleep(__FILE__, __LINE__, 0); - /* * it would be nicer only to annotate paths which are not under * pagefault_disable, however that requires a larger audit and * providing helpers like get_user_atomic. */ - if (!in_atomic() && current->mm) + if (in_atomic()) + return; + + __might_sleep(__FILE__, __LINE__, 0); + + if (current->mm) might_lock_read(¤t->mm->mmap_sem); } EXPORT_SYMBOL(might_fault); |