[PATCH 6/5] cpuset: rebind numa vma mempolicy fix

[Paul Jackson <pj@sgi.com>]

The patch:
  [PATCH 2/5] cpuset: rebind numa vma mempolicy
requires this fix to avoid a deadlock situation
in certain cpuset removal cases.

It's ok to not complete the refresh_mems() operation
if we notice we are already holding mmap_sem.  We
will try again, next time we allocate memory.

Signed-off-by: Paul Jackson <pj@sgi.com>

---

 (This fix was included in my testing, but in another
  patch that has not been sent in yet.)

 kernel/cpuset.c |    5 +++++
 1 files changed, 5 insertions(+)

--- 2.6.14-rc5-mm1-cpuset-patches.orig/kernel/cpuset.c	2005-11-03 21:18:26.783391082 -0800
+++ 2.6.14-rc5-mm1-cpuset-patches/kernel/cpuset.c	2005-11-03 23:11:15.480042373 -0800
@@ -656,7 +656,12 @@ static void refresh_mems(void)
 	if (current->cpuset_mems_generation != my_cpusets_mem_gen) {
 		struct cpuset *cs;
 		nodemask_t oldmem = current->mems_allowed;
+		struct mm_struct *mm = current->mm;
 
+		/* numa_policy_rebind() needs mmap_sem - don't nest */
+		if (!mm || !down_write_trylock(&mm->mmap_sem))
+			return;
+		up_write(&mm->mmap_sem);
 		down(&callback_sem);
 		task_lock(current);
 		cs = current->cpuset;

-- 
                          I won't rest till it's the best ...
                          Programmer, Linux Scalability
                          Paul Jackson <pj@sgi.com> 1.650.933.1373