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authorDima Zavin <dima@android.com>2010-04-27 20:57:04 -0700
committerDan Willemsen <dwillemsen@nvidia.com>2011-11-30 21:38:17 -0800
commit46af142b6690ad0adbfae0e1530596e18b2ba990 (patch)
treecc25868d36405e683d2b04439d76218652f47935 /arch
parent0a35f17ace9ac79bcb87cf1f429a0e4ff18e94c0 (diff)
[ARM] Do not call flush_cache_user_range with mmap_sem held
We can't be holding the mmap_sem while calling flush_cache_user_range because the flush can fault. If we fault on a user address, the page fault handler will try to take mmap_sem again. Since both places acquire the read lock, most of the time it succeeds. However, if another thread tries to acquire the write lock on the mmap_sem (e.g. mmap) in between the call to flush_cache_user_range and the fault, the down_read in do_page_fault will deadlock. Also, since we really can't be holding the mmap_sem while calling flush_cache_user_range AND vma is actually unused by the flush itself, get rid of vma as an argument. Change-Id: If55409bde41ad1060fa4fe7cbd4ac530d4d9a106 Signed-off-by: Dima Zavin <dima@android.com>
Diffstat (limited to 'arch')
-rw-r--r--arch/arm/include/asm/cacheflush.h2
-rw-r--r--arch/arm/kernel/traps.c4
2 files changed, 4 insertions, 2 deletions
diff --git a/arch/arm/include/asm/cacheflush.h b/arch/arm/include/asm/cacheflush.h
index d5d8d5c72682..1252a2675ca9 100644
--- a/arch/arm/include/asm/cacheflush.h
+++ b/arch/arm/include/asm/cacheflush.h
@@ -249,7 +249,7 @@ extern void flush_cache_page(struct vm_area_struct *vma, unsigned long user_addr
* Harvard caches are synchronised for the user space address range.
* This is used for the ARM private sys_cacheflush system call.
*/
-#define flush_cache_user_range(vma,start,end) \
+#define flush_cache_user_range(start,end) \
__cpuc_coherent_user_range((start) & PAGE_MASK, PAGE_ALIGN(end))
/*
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index bc9f9da782cb..4ef9f0d04e5a 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -466,7 +466,9 @@ do_cache_op(unsigned long start, unsigned long end, int flags)
if (end > vma->vm_end)
end = vma->vm_end;
- flush_cache_user_range(vma, start, end);
+ up_read(&mm->mmap_sem);
+ flush_cache_user_range(start, end);
+ return;
}
up_read(&mm->mmap_sem);
}