Messages in this thread Patch in this message | | | Date | Tue, 28 May 2013 06:27:08 -0700 | From | "tip-bot for Michael S. Tsirkin" <> | Subject | [tip:sched/mm] mm, sched: Allow uaccess in atomic with pagefault_disable() |
| |
Commit-ID: 662bbcb2747c2422cf98d3d97619509379eee466 Gitweb: http://git.kernel.org/tip/662bbcb2747c2422cf98d3d97619509379eee466 Author: Michael S. Tsirkin <mst@redhat.com> AuthorDate: Sun, 26 May 2013 17:32:23 +0300 Committer: Ingo Molnar <mingo@kernel.org> CommitDate: Tue, 28 May 2013 09:41:11 +0200
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> --- include/linux/kernel.h | 7 ++----- mm/memory.c | 11 +++++++---- 2 files changed, 9 insertions(+), 9 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h index 24719ea..4c7e2e5 100644 --- a/include/linux/kernel.h +++ b/include/linux/kernel.h @@ -193,13 +193,10 @@ extern int _cond_resched(void); (__x < 0) ? -__x : __x; \ }) -#ifdef CONFIG_PROVE_LOCKING +#if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP) void might_fault(void); #else -static inline void might_fault(void) -{ - __might_sleep(__FILE__, __LINE__, 0); -} +static inline void might_fault(void) { } #endif extern struct atomic_notifier_head panic_notifier_list; diff --git a/mm/memory.c b/mm/memory.c index c1f190f..d7d54a1 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);
| |