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Date: Fri, 24 May 2013 17:18:41 +0300 From: "Michael S. Tsirkin" <mst@...hat.com> To: linux-kernel@...r.kernel.org Cc: linux-mm@...ck.org Subject: [PATCH v3 11/11] kernel: 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@...hat.com> --- 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 c514c06..0153be1 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); -- MST -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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