cgroup/cpuset: Globally track isolated_cpus update

The current cpuset code passes a local isolcpus_updated flag around in a
number of functions to determine if external isolation related cpumasks
like wq_unbound_cpumask should be updated. It is a bit cumbersome and
makes the code more complex. Simplify the code by using a global boolean
flag "isolated_cpus_updating" to track this. This flag will be set in
isolated_cpus_update() and cleared in update_isolation_cpumasks().

No functional change is expected.

Signed-off-by: Waiman Long <longman@redhat.com>
Reviewed-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 2daf58bf0bbb7877f1f611a0ba86e9ef025368b8..90288efe53677f12ca9aa0118c0f75e3d20eaed1 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -81,6 +81,13 @@ static cpumask_var_t subpartitions_cpus;
  */
 static cpumask_var_t   isolated_cpus;
 
+/*
+ * isolated_cpus updating flag (protected by cpuset_mutex)
+ * Set if isolated_cpus is going to be updated in the current
+ * cpuset_mutex crtical section.
+ */
+static bool isolated_cpus_updating;
+
 /*
  * Housekeeping (HK_TYPE_DOMAIN) CPUs at boot
  */
@@ -1327,6 +1334,8 @@ static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus
                cpumask_or(isolated_cpus, isolated_cpus, xcpus);
        else
                cpumask_andnot(isolated_cpus, isolated_cpus, xcpus);
+
+       isolated_cpus_updating = true;
 }
 
 /*
@@ -1334,15 +1343,12 @@ static void isolated_cpus_update(int old_prs, int new_prs, struct cpumask *xcpus
  * @new_prs: new partition_root_state
  * @parent: parent cpuset
  * @xcpus: exclusive CPUs to be added
- * Return: true if isolated_cpus modified, false otherwise
  *
  * Remote partition if parent == NULL
  */
-static bool partition_xcpus_add(int new_prs, struct cpuset *parent,
+static void partition_xcpus_add(int new_prs, struct cpuset *parent,
                                struct cpumask *xcpus)
 {
-       bool isolcpus_updated;
-
        WARN_ON_ONCE(new_prs < 0);
        lockdep_assert_held(&callback_lock);
        if (!parent)
@@ -1352,13 +1358,11 @@ static bool partition_xcpus_add(int new_prs, struct cpuset *parent,
        if (parent == &top_cpuset)
                cpumask_or(subpartitions_cpus, subpartitions_cpus, xcpus);
 
-       isolcpus_updated = (new_prs != parent->partition_root_state);
-       if (isolcpus_updated)
+       if (new_prs != parent->partition_root_state)
                isolated_cpus_update(parent->partition_root_state, new_prs,
                                     xcpus);
 
        cpumask_andnot(parent->effective_cpus, parent->effective_cpus, xcpus);
-       return isolcpus_updated;
 }
 
 /*
@@ -1366,15 +1370,12 @@ static bool partition_xcpus_add(int new_prs, struct cpuset *parent,
  * @old_prs: old partition_root_state
  * @parent: parent cpuset
  * @xcpus: exclusive CPUs to be removed
- * Return: true if isolated_cpus modified, false otherwise
  *
  * Remote partition if parent == NULL
  */
-static bool partition_xcpus_del(int old_prs, struct cpuset *parent,
+static void partition_xcpus_del(int old_prs, struct cpuset *parent,
                                struct cpumask *xcpus)
 {
-       bool isolcpus_updated;
-
        WARN_ON_ONCE(old_prs < 0);
        lockdep_assert_held(&callback_lock);
        if (!parent)
@@ -1383,14 +1384,12 @@ static bool partition_xcpus_del(int old_prs, struct cpuset *parent,
        if (parent == &top_cpuset)
                cpumask_andnot(subpartitions_cpus, subpartitions_cpus, xcpus);
 
-       isolcpus_updated = (old_prs != parent->partition_root_state);
-       if (isolcpus_updated)
+       if (old_prs != parent->partition_root_state)
                isolated_cpus_update(old_prs, parent->partition_root_state,
                                     xcpus);
 
        cpumask_and(xcpus, xcpus, cpu_active_mask);
        cpumask_or(parent->effective_cpus, parent->effective_cpus, xcpus);
-       return isolcpus_updated;
 }
 
 /*
@@ -1452,17 +1451,24 @@ static bool prstate_housekeeping_conflict(int prstate, struct cpumask *new_cpus)
        return false;
 }
 
-static void update_isolation_cpumasks(bool isolcpus_updated)
+/*
+ * update_isolation_cpumasks - Update external isolation related CPU masks
+ *
+ * The following external CPU masks will be updated if necessary:
+ * - workqueue unbound cpumask
+ */
+static void update_isolation_cpumasks(void)
 {
        int ret;
 
-       lockdep_assert_cpus_held();
-
-       if (!isolcpus_updated)
+       if (!isolated_cpus_updating)
                return;
 
+       lockdep_assert_cpus_held();
+
        ret = workqueue_unbound_exclude_cpumask(isolated_cpus);
        WARN_ON_ONCE(ret < 0);
+       isolated_cpus_updating = false;
 }
 
 /**
@@ -1587,8 +1593,6 @@ static inline bool is_local_partition(struct cpuset *cs)
 static int remote_partition_enable(struct cpuset *cs, int new_prs,
                                   struct tmpmasks *tmp)
 {
-       bool isolcpus_updated;
-
        /*
         * The user must have sysadmin privilege.
         */
@@ -1616,11 +1620,11 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
                return PERR_HKEEPING;
 
        spin_lock_irq(&callback_lock);
-       isolcpus_updated = partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
+       partition_xcpus_add(new_prs, NULL, tmp->new_cpus);
        list_add(&cs->remote_sibling, &remote_children);
        cpumask_copy(cs->effective_xcpus, tmp->new_cpus);
        spin_unlock_irq(&callback_lock);
-       update_isolation_cpumasks(isolcpus_updated);
+       update_isolation_cpumasks();
        cpuset_force_rebuild();
        cs->prs_err = 0;
 
@@ -1643,15 +1647,12 @@ static int remote_partition_enable(struct cpuset *cs, int new_prs,
  */
 static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
 {
-       bool isolcpus_updated;
-
        WARN_ON_ONCE(!is_remote_partition(cs));
        WARN_ON_ONCE(!cpumask_subset(cs->effective_xcpus, subpartitions_cpus));
 
        spin_lock_irq(&callback_lock);
        list_del_init(&cs->remote_sibling);
-       isolcpus_updated = partition_xcpus_del(cs->partition_root_state,
-                                              NULL, cs->effective_xcpus);
+       partition_xcpus_del(cs->partition_root_state, NULL, cs->effective_xcpus);
        if (cs->prs_err)
                cs->partition_root_state = -cs->partition_root_state;
        else
@@ -1661,7 +1662,7 @@ static void remote_partition_disable(struct cpuset *cs, struct tmpmasks *tmp)
        compute_excpus(cs, cs->effective_xcpus);
        reset_partition_data(cs);
        spin_unlock_irq(&callback_lock);
-       update_isolation_cpumasks(isolcpus_updated);
+       update_isolation_cpumasks();
        cpuset_force_rebuild();
 
        /*
@@ -1686,7 +1687,6 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
 {
        bool adding, deleting;
        int prs = cs->partition_root_state;
-       int isolcpus_updated = 0;
 
        if (WARN_ON_ONCE(!is_remote_partition(cs)))
                return;
@@ -1722,9 +1722,9 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
 
        spin_lock_irq(&callback_lock);
        if (adding)
-               isolcpus_updated += partition_xcpus_add(prs, NULL, tmp->addmask);
+               partition_xcpus_add(prs, NULL, tmp->addmask);
        if (deleting)
-               isolcpus_updated += partition_xcpus_del(prs, NULL, tmp->delmask);
+               partition_xcpus_del(prs, NULL, tmp->delmask);
        /*
         * Need to update effective_xcpus and exclusive_cpus now as
         * update_sibling_cpumasks() below may iterate back to the same cs.
@@ -1733,7 +1733,7 @@ static void remote_cpus_update(struct cpuset *cs, struct cpumask *xcpus,
        if (xcpus)
                cpumask_copy(cs->exclusive_cpus, xcpus);
        spin_unlock_irq(&callback_lock);
-       update_isolation_cpumasks(isolcpus_updated);
+       update_isolation_cpumasks();
        if (adding || deleting)
                cpuset_force_rebuild();
 
@@ -1794,7 +1794,6 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
        int deleting;   /* Deleting cpus from parent's effective_cpus   */
        int old_prs, new_prs;
        int part_error = PERR_NONE;     /* Partition error? */
-       int isolcpus_updated = 0;
        struct cpumask *xcpus = user_xcpus(cs);
        int parent_prs = parent->partition_root_state;
        bool nocpu;
@@ -2073,14 +2072,12 @@ static int update_parent_effective_cpumask(struct cpuset *cs, int cmd,
         * and vice versa.
         */
        if (adding)
-               isolcpus_updated += partition_xcpus_del(old_prs, parent,
-                                                       tmp->addmask);
+               partition_xcpus_del(old_prs, parent, tmp->addmask);
        if (deleting)
-               isolcpus_updated += partition_xcpus_add(new_prs, parent,
-                                                       tmp->delmask);
+               partition_xcpus_add(new_prs, parent, tmp->delmask);
 
        spin_unlock_irq(&callback_lock);
-       update_isolation_cpumasks(isolcpus_updated);
+       update_isolation_cpumasks();
 
        if ((old_prs != new_prs) && (cmd == partcmd_update))
                update_partition_exclusive_flag(cs, new_prs);
@@ -3103,7 +3100,7 @@ static int update_prstate(struct cpuset *cs, int new_prs)
        else if (isolcpus_updated)
                isolated_cpus_update(old_prs, new_prs, cs->effective_xcpus);
        spin_unlock_irq(&callback_lock);
-       update_isolation_cpumasks(isolcpus_updated);
+       update_isolation_cpumasks();
 
        /* Force update if switching back to member & update effective_xcpus */
        update_cpumasks_hier(cs, &tmpmask, !new_prs);