From: Adam Iwaniuk <[email protected]> We can't be holding the mmap_sem while calling __flush_XXX_region/flush_icache_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_XXX_region/flush_icache_range and the fault, the down_read in do_page_fault will deadlock.
Signed-off-by: Adam Iwaniuk <[email protected]> --- arch/sh/kernel/sys_sh.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/sh/kernel/sys_sh.c b/arch/sh/kernel/sys_sh.c index 8c6a350..4aa294c 100644 --- a/arch/sh/kernel/sys_sh.c +++ b/arch/sh/kernel/sys_sh.c @@ -74,6 +74,7 @@ asmlinkage int sys_cacheflush(unsigned long addr, unsigned long len, int op) up_read(¤t->mm->mmap_sem); return -EFAULT; } + up_read(¤t->mm->mmap_sem); switch (op & CACHEFLUSH_D_PURGE) { case CACHEFLUSH_D_INVAL: @@ -90,6 +91,5 @@ asmlinkage int sys_cacheflush(unsigned long addr, unsigned long len, int op) if (op & CACHEFLUSH_I) flush_icache_range(addr, addr+len); - up_read(¤t->mm->mmap_sem); return 0; } -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
