From: Dima Zavin Date: Wed, 28 Apr 2010 03:57:04 +0000 (-0700) Subject: [ARM] Do not call flush_cache_user_range with mmap_sem held X-Git-Tag: firefly_0821_release~7613^2~738 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=076f80cb854992a6731e20058ddb0e2ba10220aa;p=firefly-linux-kernel-4.4.55.git [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 --- 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 d52eec268b47..d1a0892ae262 100644 --- a/arch/arm/kernel/traps.c +++ b/arch/arm/kernel/traps.c @@ -451,7 +451,9 @@ 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); }