Reduce cpuset.c write_lock_irq() to read_lock()

cpuset.c:update_nodemask() uses a write_lock_irq() on tasklist_lock to
block concurrent forks; a read_lock() suffices and is less intrusive.

Signed-off-by: Paul Menage<menage@google.com>
Acked-by: Paul Jackson <pj@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 4c49188cc49b..824b1c01f410 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -981,10 +981,10 @@ static int update_nodemask(struct cpuset *cs, char *buf)
                 mmarray = kmalloc(ntasks * sizeof(*mmarray), GFP_KERNEL);
                 if (!mmarray)
                         goto done;
-                write_lock_irq(&tasklist_lock);         /* block fork */
+                read_lock(&tasklist_lock);              /* block fork */
                 if (atomic_read(&cs->count) <= ntasks)
                         break;                          /* got enough */
-                write_unlock_irq(&tasklist_lock);       /* try again */
+                read_unlock(&tasklist_lock);            /* try again */
                 kfree(mmarray);
         }
 
@@ -1006,7 +1006,7 @@ static int update_nodemask(struct cpuset *cs, char *buf)
                         continue;
                 mmarray[n++] = mm;
         } while_each_thread(g, p);
-        write_unlock_irq(&tasklist_lock);
+        read_unlock(&tasklist_lock);
 
         /*
          * Now that we've dropped the tasklist spinlock, we can