From c6669c223a409199a45bb8f31a2e160ee26d19cc Mon Sep 17 00:00:00 2001 From: Graf Yang Date: Wed, 13 Jan 2010 06:09:34 +0000 Subject: [PATCH] Blackfin: fix up mm locking in address dumping The locking code in the address dumper needs to grab the mm's mmap_sem so that other CPUs do not get an inconsistent view. On UP systems this really wasn't a problem, but it is easy to trigger a race on SMP systems when another CPU removes a mapping. Signed-off-by: Graf Yang Signed-off-by: Mike Frysinger --- arch/blackfin/kernel/traps.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/arch/blackfin/kernel/traps.c b/arch/blackfin/kernel/traps.c index 870d74b..8576680 100644 --- a/arch/blackfin/kernel/traps.c +++ b/arch/blackfin/kernel/traps.c @@ -138,6 +138,12 @@ static void decode_address(char *buf, unsigned long address) if (!mm) continue; + if (!down_read_trylock(&mm->mmap_sem)) { + if (!in_atomic) + mmput(mm); + continue; + } + for (n = rb_first(&mm->mm_rb); n; n = rb_next(n)) { struct vm_area_struct *vma; @@ -177,6 +183,7 @@ static void decode_address(char *buf, unsigned long address) sprintf(buf, "[ %s vma:0x%lx-0x%lx]", name, vma->vm_start, vma->vm_end); + up_read(&mm->mmap_sem); if (!in_atomic) mmput(mm); @@ -186,11 +193,16 @@ static void decode_address(char *buf, unsigned long address) goto done; } } + + up_read(&mm->mmap_sem); if (!in_atomic) mmput(mm); } - /* we were unable to find this address anywhere */ + /* + * we were unable to find this address anywhere, + * or some MMs were skipped because they were in use. + */ sprintf(buf, "/* kernel dynamic memory */"); done: -- 2.7.4