[RFC 2/2] mm, sched: trigger might_sleep() in might_fault() when atomic
From: David Hildenbrand <hidden>
Date: 2014-11-25 11:43:43
Also in:
linux-arch, lkml
Subsystem:
memory management, memory management - core, the rest · Maintainers:
Andrew Morton, David Hildenbrand, Linus Torvalds
Commit 662bbcb2747c2422cf98d3d97619509379eee466 disabled in atomic checks for all user access code (that uses might_fault()). That change basically disabled CONFIG_DEBUG_ATOMIC_SLEEP for all user access functions. However, this is a mighty debugging aid that we want. If user memory is to be accessed while pagefault_disabled() is set, the atomic variants of copy_(to|from)_user can be used. This patch reverts commit 662bbcb2747c2422cf98d3d97619509379eee466 taking care of the !MMU optimization. Signed-off-by: David Hildenbrand <redacted> --- include/linux/kernel.h | 8 ++++++-- mm/memory.c | 11 ++++------- 2 files changed, 10 insertions(+), 9 deletions(-)
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 3d770f55..1d3397c 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h@@ -225,9 +225,13 @@ static inline u32 reciprocal_scale(u32 val, u32 ep_ro) return (u32)(((u64) val * ep_ro) >> 32); } -#if defined(CONFIG_MMU) && \ - (defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)) +#if defined(CONFIG_MMU) && defined(CONFIG_PROVE_LOCKING) void might_fault(void); +#elif defined(CONFIG_MMU) && defined(CONFIG_DEBUG_ATOMIC_SLEEP) +static inline void might_fault(void) +{ + __might_sleep(__FILE__, __LINE__, 0); +} #else static inline void might_fault(void) { } #endif
diff --git a/mm/memory.c b/mm/memory.c
index 3e50383..fe0c815 100644
--- a/mm/memory.c
+++ b/mm/memory.c@@ -3699,7 +3699,7 @@ void print_vma_addr(char *prefix, unsigned long ip) up_read(&mm->mmap_sem); } -#if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP) +#ifdef CONFIG_PROVE_LOCKING void might_fault(void) { /*
@@ -3711,17 +3711,14 @@ 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()) - return; - - __might_sleep(__FILE__, __LINE__, 0); - - if (current->mm) + if (!in_atomic() && current->mm) might_lock_read(¤t->mm->mmap_sem); } EXPORT_SYMBOL(might_fault);
--
1.8.5.5