1 files changed, 46 insertions, 138 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index af5a83d52187..7e75a41bd508 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -97,12 +97,6 @@ struct cpuset {
 
         struct cpuset *parent;          /* my parent */
 
-        /*
-         * Copy of global cpuset_mems_generation as of the most
-         * recent time this cpuset changed its mems_allowed.
-         */
-        int mems_generation;
-
         struct fmeter fmeter;           /* memory_pressure filter */
 
         /* partition number for rebuild_sched_domains() */
@@ -176,27 +170,6 @@ static inline int is_spread_slab(const struct cpuset *cs)
         return test_bit(CS_SPREAD_SLAB, &cs->flags);
 }
 
-/*
- * Increment this integer everytime any cpuset changes its
- * mems_allowed value.  Users of cpusets can track this generation
- * number, and avoid having to lock and reload mems_allowed unless
- * the cpuset they're using changes generation.
- *
- * A single, global generation is needed because cpuset_attach_task() could
- * reattach a task to a different cpuset, which must not have its
- * generation numbers aliased with those of that tasks previous cpuset.
- *
- * Generations are needed for mems_allowed because one task cannot
- * modify another's memory placement.  So we must enable every task,
- * on every visit to __alloc_pages(), to efficiently check whether
- * its current->cpuset->mems_allowed has changed, requiring an update
- * of its current->mems_allowed.
- *
- * Since writes to cpuset_mems_generation are guarded by the cgroup lock
- * there is no need to mark it atomic.
- */
-static int cpuset_mems_generation;
-
 static struct cpuset top_cpuset = {
         .flags = ((1 << CS_CPU_EXCLUSIVE) | (1 << CS_MEM_EXCLUSIVE)),
 };
@@ -228,8 +201,9 @@ static struct cpuset top_cpuset = {
  * If a task is only holding callback_mutex, then it has read-only
  * access to cpusets.
  *
- * The task_struct fields mems_allowed and mems_generation may only
- * be accessed in the context of that task, so require no locks.
+ * Now, the task_struct fields mems_allowed and mempolicy may be changed
+ * by other task, we use alloc_lock in the task_struct fields to protect
+ * them.
  *
  * The cpuset_common_file_read() handlers only hold callback_mutex across
  * small pieces of code, such as when reading out possibly multi-word
@@ -349,69 +323,6 @@ static void cpuset_update_task_spread_flag(struct cpuset *cs,
                 tsk->flags &= ~PF_SPREAD_SLAB;
 }
 
-/**
- * cpuset_update_task_memory_state - update task memory placement
- *
- * If the current tasks cpusets mems_allowed changed behind our
- * backs, update current->mems_allowed, mems_generation and task NUMA
- * mempolicy to the new value.
- *
- * Task mempolicy is updated by rebinding it relative to the
- * current->cpuset if a task has its memory placement changed.
- * Do not call this routine if in_interrupt().
- *
- * Call without callback_mutex or task_lock() held.  May be
- * called with or without cgroup_mutex held.  Thanks in part to
- * 'the_top_cpuset_hack', the task's cpuset pointer will never
- * be NULL.  This routine also might acquire callback_mutex during
- * call.
- *
- * Reading current->cpuset->mems_generation doesn't need task_lock
- * to guard the current->cpuset derefence, because it is guarded
- * from concurrent freeing of current->cpuset using RCU.
- *
- * The rcu_dereference() is technically probably not needed,
- * as I don't actually mind if I see a new cpuset pointer but
- * an old value of mems_generation.  However this really only
- * matters on alpha systems using cpusets heavily.  If I dropped
- * that rcu_dereference(), it would save them a memory barrier.
- * For all other arch's, rcu_dereference is a no-op anyway, and for
- * alpha systems not using cpusets, another planned optimization,
- * avoiding the rcu critical section for tasks in the root cpuset
- * which is statically allocated, so can't vanish, will make this
- * irrelevant.  Better to use RCU as intended, than to engage in
- * some cute trick to save a memory barrier that is impossible to
- * test, for alpha systems using cpusets heavily, which might not
- * even exist.
- *
- * This routine is needed to update the per-task mems_allowed data,
- * within the tasks context, when it is trying to allocate memory
- * (in various mm/mempolicy.c routines) and notices that some other
- * task has been modifying its cpuset.
- */
-
-void cpuset_update_task_memory_state(void)
-{
-        int my_cpusets_mem_gen;
-        struct task_struct *tsk = current;
-        struct cpuset *cs;
-
-        rcu_read_lock();
-        my_cpusets_mem_gen = task_cs(tsk)->mems_generation;
-        rcu_read_unlock();
-
-        if (my_cpusets_mem_gen != tsk->cpuset_mems_generation) {
-                mutex_lock(&callback_mutex);
-                task_lock(tsk);
-                cs = task_cs(tsk); /* Maybe changed when task not locked */
-                guarantee_online_mems(cs, &tsk->mems_allowed);
-                tsk->cpuset_mems_generation = cs->mems_generation;
-                task_unlock(tsk);
-                mutex_unlock(&callback_mutex);
-                mpol_rebind_task(tsk, &tsk->mems_allowed);
-        }
-}
-
 /*
  * is_cpuset_subset(p, q) - Is cpuset p a subset of cpuset q?
  *
@@ -1017,14 +928,6 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs,
  *    other task, the task_struct mems_allowed that we are hacking
  *    is for our current task, which must allocate new pages for that
  *    migrating memory region.
- *
- *    We call cpuset_update_task_memory_state() before hacking
- *    our tasks mems_allowed, so that we are assured of being in
- *    sync with our tasks cpuset, and in particular, callbacks to
- *    cpuset_update_task_memory_state() from nested page allocations
- *    won't see any mismatch of our cpuset and task mems_generation
- *    values, so won't overwrite our hacked tasks mems_allowed
- *    nodemask.
  */
 
 static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
@@ -1032,22 +935,37 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
 {
         struct task_struct *tsk = current;
 
-        cpuset_update_task_memory_state();
-
-        mutex_lock(&callback_mutex);
         tsk->mems_allowed = *to;
-        mutex_unlock(&callback_mutex);
 
         do_migrate_pages(mm, from, to, MPOL_MF_MOVE_ALL);
 
-        mutex_lock(&callback_mutex);
         guarantee_online_mems(task_cs(tsk),&tsk->mems_allowed);
-        mutex_unlock(&callback_mutex);
 }
 
 /*
- * Rebind task's vmas to cpuset's new mems_allowed, and migrate pages to new
- * nodes if memory_migrate flag is set. Called with cgroup_mutex held.
+ * cpuset_change_task_nodemask - change task's mems_allowed and mempolicy
+ * @tsk: the task to change
+ * @newmems: new nodes that the task will be set
+ *
+ * In order to avoid seeing no nodes if the old and new nodes are disjoint,
+ * we structure updates as setting all new allowed nodes, then clearing newly
+ * disallowed ones.
+ *
+ * Called with task's alloc_lock held
+ */
+static void cpuset_change_task_nodemask(struct task_struct *tsk,
+                                        nodemask_t *newmems)
+{
+        nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
+        mpol_rebind_task(tsk, &tsk->mems_allowed);
+        mpol_rebind_task(tsk, newmems);
+        tsk->mems_allowed = *newmems;
+}
+
+/*
+ * Update task's mems_allowed and rebind its mempolicy and vmas' mempolicy
+ * of it to cpuset's new mems_allowed, and migrate pages to new nodes if
+ * memory_migrate flag is set. Called with cgroup_mutex held.
  */
 static void cpuset_change_nodemask(struct task_struct *p,
                                    struct cgroup_scanner *scan)
@@ -1056,12 +974,19 @@ static void cpuset_change_nodemask(struct task_struct *p,
         struct cpuset *cs;
         int migrate;
         const nodemask_t *oldmem = scan->data;
+        nodemask_t newmems;
+
+        cs = cgroup_cs(scan->cg);
+        guarantee_online_mems(cs, &newmems);
+
+        task_lock(p);
+        cpuset_change_task_nodemask(p, &newmems);
+        task_unlock(p);
 
         mm = get_task_mm(p);
         if (!mm)
                 return;
 
-        cs = cgroup_cs(scan->cg);
         migrate = is_memory_migrate(cs);
 
         mpol_rebind_mm(mm, &cs->mems_allowed);
@@ -1114,10 +1039,10 @@ static void update_tasks_nodemask(struct cpuset *cs, const nodemask_t *oldmem,
 /*
  * Handle user request to change the 'mems' memory placement
  * of a cpuset.  Needs to validate the request, update the
- * cpusets mems_allowed and mems_generation, and for each
- * task in the cpuset, rebind any vma mempolicies and if
- * the cpuset is marked 'memory_migrate', migrate the tasks
- * pages to the new memory.
+ * cpusets mems_allowed, and for each task in the cpuset,
+ * update mems_allowed and rebind task's mempolicy and any vma
+ * mempolicies and if the cpuset is marked 'memory_migrate',
+ * migrate the tasks pages to the new memory.
  *
  * Call with cgroup_mutex held.  May take callback_mutex during call.
  * Will take tasklist_lock, scan tasklist for tasks in cpuset cs,
@@ -1170,7 +1095,6 @@ static int update_nodemask(struct cpuset *cs, struct cpuset *trialcs,
 
         mutex_lock(&callback_mutex);
         cs->mems_allowed = trialcs->mems_allowed;
-        cs->mems_generation = cpuset_mems_generation++;
         mutex_unlock(&callback_mutex);
 
         update_tasks_nodemask(cs, &oldmem, &heap);
@@ -1434,15 +1358,18 @@ static void cpuset_attach(struct cgroup_subsys *ss,
 
         if (cs == &top_cpuset) {
                 cpumask_copy(cpus_attach, cpu_possible_mask);
+                to = node_possible_map;
         } else {
-                mutex_lock(&callback_mutex);
                 guarantee_online_cpus(cs, cpus_attach);
-                mutex_unlock(&callback_mutex);
+                guarantee_online_mems(cs, &to);
         }
         err = set_cpus_allowed_ptr(tsk, cpus_attach);
         if (err)
                 return;
 
+        task_lock(tsk);
+        cpuset_change_task_nodemask(tsk, &to);
+        task_unlock(tsk);
         cpuset_update_task_spread_flag(cs, tsk);
 
         from = oldcs->mems_allowed;
@@ -1848,8 +1775,6 @@ static struct cgroup_subsys_state *cpuset_create(
         struct cpuset *parent;
 
         if (!cont->parent) {
-                /* This is early initialization for the top cgroup */
-                top_cpuset.mems_generation = cpuset_mems_generation++;
                 return &top_cpuset.css;
         }
         parent = cgroup_cs(cont->parent);
@@ -1861,7 +1786,6 @@ static struct cgroup_subsys_state *cpuset_create(
                 return ERR_PTR(-ENOMEM);
         }
 
-        cpuset_update_task_memory_state();
         cs->flags = 0;
         if (is_spread_page(parent))
                 set_bit(CS_SPREAD_PAGE, &cs->flags);
@@ -1870,7 +1794,6 @@ static struct cgroup_subsys_state *cpuset_create(
         set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
         cpumask_clear(cs->cpus_allowed);
         nodes_clear(cs->mems_allowed);
-        cs->mems_generation = cpuset_mems_generation++;
         fmeter_init(&cs->fmeter);
         cs->relax_domain_level = -1;
 
@@ -1889,8 +1812,6 @@ static void cpuset_destroy(struct cgroup_subsys *ss, struct cgroup *cont)
 {
         struct cpuset *cs = cgroup_cs(cont);
 
-        cpuset_update_task_memory_state();
-
         if (is_sched_load_balance(cs))
                 update_flag(CS_SCHED_LOAD_BALANCE, cs, 0);
 
@@ -1911,21 +1832,6 @@ struct cgroup_subsys cpuset_subsys = {
         .early_init = 1,
 };
 
-/*
- * cpuset_init_early - just enough so that the calls to
- * cpuset_update_task_memory_state() in early init code
- * are harmless.
- */
-
-int __init cpuset_init_early(void)
-{
-        alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_NOWAIT);
-
-        top_cpuset.mems_generation = cpuset_mems_generation++;
-        return 0;
-}
-
-
 /**
  * cpuset_init - initialize cpusets at system boot
  *
@@ -1936,11 +1842,13 @@ int __init cpuset_init(void)
 {
         int err = 0;
 
+        if (!alloc_cpumask_var(&top_cpuset.cpus_allowed, GFP_KERNEL))
+                BUG();
+
         cpumask_setall(top_cpuset.cpus_allowed);
         nodes_setall(top_cpuset.mems_allowed);
 
         fmeter_init(&top_cpuset.fmeter);
-        top_cpuset.mems_generation = cpuset_mems_generation++;
         set_bit(CS_SCHED_LOAD_BALANCE, &top_cpuset.flags);
         top_cpuset.relax_domain_level = -1;