Merge rsync://rsync.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6 into for...

[powerpc.git] / kernel / cpuset.c

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index c232dc0..1a649f2 100644 (file)
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -762,6 +762,8 @@ static int validate_change(const struct cpuset *cur, const struct cpuset *trial)
  *
  * Call with manage_mutex held.  May nest a call to the
  * lock_cpu_hotplug()/unlock_cpu_hotplug() pair.
+ * Must not be called holding callback_mutex, because we must
+ * not call lock_cpu_hotplug() while holding callback_mutex.
  */
 
 static void update_cpu_domains(struct cpuset *cur)
@@ -781,7 +783,7 @@ static void update_cpu_domains(struct cpuset *cur)
                if (is_cpu_exclusive(c))
                        cpus_andnot(pspan, pspan, c->cpus_allowed);
        }
-       if (is_removed(cur) || !is_cpu_exclusive(cur)) {
+       if (!is_cpu_exclusive(cur)) {
                cpus_or(pspan, pspan, cur->cpus_allowed);
                if (cpus_equal(pspan, cur->cpus_allowed))
                        return;
@@ -1917,6 +1919,17 @@ static int cpuset_mkdir(struct inode *dir, struct dentry *dentry, int mode)
        return cpuset_create(c_parent, dentry->d_name.name, mode | S_IFDIR);
 }
 
+/*
+ * Locking note on the strange update_flag() call below:
+ *
+ * If the cpuset being removed is marked cpu_exclusive, then simulate
+ * turning cpu_exclusive off, which will call update_cpu_domains().
+ * The lock_cpu_hotplug() call in update_cpu_domains() must not be
+ * made while holding callback_mutex.  Elsewhere the kernel nests
+ * callback_mutex inside lock_cpu_hotplug() calls.  So the reverse
+ * nesting would risk an ABBA deadlock.
+ */
+
 static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry)
 {
        struct cpuset *cs = dentry->d_fsdata;
@@ -1936,11 +1949,16 @@ static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry)
                mutex_unlock(&manage_mutex);
                return -EBUSY;
        }
+       if (is_cpu_exclusive(cs)) {
+               int retval = update_flag(CS_CPU_EXCLUSIVE, cs, "0");
+               if (retval < 0) {
+                       mutex_unlock(&manage_mutex);
+                       return retval;
+               }
+       }
        parent = cs->parent;
        mutex_lock(&callback_mutex);
        set_bit(CS_REMOVED, &cs->flags);
-       if (is_cpu_exclusive(cs))
-               update_cpu_domains(cs);
        list_del(&cs->sibling); /* delete my sibling from parent->children */
        spin_lock(&cs->dentry->d_lock);
        d = dget(cs->dentry);