*/
static DECLARE_MUTEX(cpuset_sem);
+static struct task_struct *cpuset_sem_owner;
+static int cpuset_sem_depth;
+
+/*
+ * The global cpuset semaphore cpuset_sem can be needed by the
+ * memory allocator to update a tasks mems_allowed (see the calls
+ * to cpuset_update_current_mems_allowed()) or to walk up the
+ * cpuset hierarchy to find a mem_exclusive cpuset see the calls
+ * to cpuset_excl_nodes_overlap()).
+ *
+ * But if the memory allocation is being done by cpuset.c code, it
+ * usually already holds cpuset_sem. Double tripping on a kernel
+ * semaphore deadlocks the current task, and any other task that
+ * subsequently tries to obtain the lock.
+ *
+ * Run all up's and down's on cpuset_sem through the following
+ * wrappers, which will detect this nested locking, and avoid
+ * deadlocking.
+ */
+
+static inline void cpuset_down(struct semaphore *psem)
+{
+ if (cpuset_sem_owner != current) {
+ down(psem);
+ cpuset_sem_owner = current;
+ }
+ cpuset_sem_depth++;
+}
+
+static inline void cpuset_up(struct semaphore *psem)
+{
+ if (--cpuset_sem_depth == 0) {
+ cpuset_sem_owner = NULL;
+ up(psem);
+ }
+}
/*
* A couple of forward declarations required, due to cyclic reference loop:
* Refresh current tasks mems_allowed and mems_generation from
* current tasks cpuset. Call with cpuset_sem held.
*
- * Be sure to call refresh_mems() on any cpuset operation which
- * (1) holds cpuset_sem, and (2) might possibly alloc memory.
- * Call after obtaining cpuset_sem lock, before any possible
- * allocation. Otherwise one risks trying to allocate memory
- * while the task cpuset_mems_generation is not the same as
- * the mems_generation in its cpuset, which would deadlock on
- * cpuset_sem in cpuset_update_current_mems_allowed().
- *
- * Since we hold cpuset_sem, once refresh_mems() is called, the
- * test (current->cpuset_mems_generation != cs->mems_generation)
- * in cpuset_update_current_mems_allowed() will remain false,
- * until we drop cpuset_sem. Anyone else who would change our
- * cpusets mems_generation needs to lock cpuset_sem first.
+ * 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.
*/
static void refresh_mems(void)
* Call with cpuset_sem held. May nest a call to the
* lock_cpu_hotplug()/unlock_cpu_hotplug() pair.
*/
+
static void update_cpu_domains(struct cpuset *cur)
{
struct cpuset *c, *par = cur->parent;
if (par == NULL || cpus_empty(cur->cpus_allowed))
return;
- /*
- * Hack to avoid 2.6.13 partial node dynamic sched domain bug.
- * Require the 'cpu_exclusive' cpuset to include all (or none)
- * of the CPUs on each node, or return w/o changing sched domains.
- * Remove this hack when dynamic sched domains fixed.
- */
- {
- int i, j;
-
- for_each_cpu_mask(i, cur->cpus_allowed) {
- cpumask_t mask = node_to_cpumask(cpu_to_node(i));
-
- for_each_cpu_mask(j, mask) {
- if (!cpu_isset(j, cur->cpus_allowed))
- return;
- }
- }
- }
-
/*
* Get all cpus from parent's cpus_allowed not part of exclusive
* children
}
buffer[nbytes] = 0; /* nul-terminate */
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
if (is_removed(cs)) {
retval = -ENODEV;
if (retval == 0)
retval = nbytes;
out2:
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
cpuset_release_agent(pathbuf);
out1:
kfree(buffer);
{
cpumask_t mask;
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
mask = cs->cpus_allowed;
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
return cpulist_scnprintf(page, PAGE_SIZE, mask);
}
{
nodemask_t mask;
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
mask = cs->mems_allowed;
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
return nodelist_scnprintf(page, PAGE_SIZE, mask);
}
*s++ = '\n';
*s = '\0';
+ /* Do nothing if *ppos is at the eof or beyond the eof. */
+ if (s - page <= *ppos)
+ return 0;
+
start = page + *ppos;
n = s - start;
retval = n - copy_to_user(buf, start, min(n, nbytes));
if (!cs)
return -ENOMEM;
- down(&cpuset_sem);
- refresh_mems();
+ cpuset_down(&cpuset_sem);
cs->flags = 0;
if (notify_on_release(parent))
set_bit(CS_NOTIFY_ON_RELEASE, &cs->flags);
* will down() this new directory's i_sem and if we race with
* another mkdir, we might deadlock.
*/
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
err = cpuset_populate_dir(cs->dentry);
/* If err < 0, we have a half-filled directory - oh well ;) */
return 0;
err:
list_del(&cs->sibling);
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
kfree(cs);
return err;
}
/* the vfs holds both inode->i_sem already */
- down(&cpuset_sem);
- refresh_mems();
+ cpuset_down(&cpuset_sem);
if (atomic_read(&cs->count) > 0) {
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
return -EBUSY;
}
if (!list_empty(&cs->children)) {
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
return -EBUSY;
}
parent = cs->parent;
spin_unlock(&d->d_lock);
cpuset_d_remove_dir(d);
dput(d);
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
cpuset_release_agent(pathbuf);
return 0;
}
if (notify_on_release(cs)) {
char *pathbuf = NULL;
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
if (atomic_dec_and_test(&cs->count))
check_for_release(cs, &pathbuf);
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
cpuset_release_agent(pathbuf);
} else {
atomic_dec(&cs->count);
{
cpumask_t mask;
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
task_lock((struct task_struct *)tsk);
guarantee_online_cpus(tsk->cpuset, &mask);
task_unlock((struct task_struct *)tsk);
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
return mask;
}
if (!cs)
return; /* task is exiting */
if (current->cpuset_mems_generation != cs->mems_generation) {
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
refresh_mems();
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
}
}
return 0;
}
+/*
+ * nearest_exclusive_ancestor() - Returns the nearest mem_exclusive
+ * ancestor to the specified cpuset. Call while holding cpuset_sem.
+ * If no ancestor is mem_exclusive (an unusual configuration), then
+ * returns the root cpuset.
+ */
+static const struct cpuset *nearest_exclusive_ancestor(const struct cpuset *cs)
+{
+ while (!is_mem_exclusive(cs) && cs->parent)
+ cs = cs->parent;
+ return cs;
+}
+
/**
- * cpuset_zone_allowed - is zone z allowed in current->mems_allowed
- * @z: zone in question
+ * cpuset_zone_allowed - Can we allocate memory on zone z's memory node?
+ * @z: is this zone on an allowed node?
+ * @gfp_mask: memory allocation flags (we use __GFP_HARDWALL)
*
- * Is zone z allowed in current->mems_allowed, or is
- * the CPU in interrupt context? (zone is always allowed in this case)
- */
-int cpuset_zone_allowed(struct zone *z)
+ * If we're in interrupt, yes, we can always allocate. If zone
+ * z's node is in our tasks mems_allowed, yes. If it's not a
+ * __GFP_HARDWALL request and this zone's nodes is in the nearest
+ * mem_exclusive cpuset ancestor to this tasks cpuset, yes.
+ * Otherwise, no.
+ *
+ * GFP_USER allocations are marked with the __GFP_HARDWALL bit,
+ * and do not allow allocations outside the current tasks cpuset.
+ * GFP_KERNEL allocations are not so marked, so can escape to the
+ * nearest mem_exclusive ancestor cpuset.
+ *
+ * Scanning up parent cpusets requires cpuset_sem. The __alloc_pages()
+ * routine only calls here with __GFP_HARDWALL bit _not_ set if
+ * it's a GFP_KERNEL allocation, and all nodes in the current tasks
+ * mems_allowed came up empty on the first pass over the zonelist.
+ * So only GFP_KERNEL allocations, if all nodes in the cpuset are
+ * short of memory, might require taking the cpuset_sem semaphore.
+ *
+ * The first loop over the zonelist in mm/page_alloc.c:__alloc_pages()
+ * calls here with __GFP_HARDWALL always set in gfp_mask, enforcing
+ * hardwall cpusets - no allocation on a node outside the cpuset is
+ * allowed (unless in interrupt, of course).
+ *
+ * The second loop doesn't even call here for GFP_ATOMIC requests
+ * (if the __alloc_pages() local variable 'wait' is set). That check
+ * and the checks below have the combined affect in the second loop of
+ * the __alloc_pages() routine that:
+ * in_interrupt - any node ok (current task context irrelevant)
+ * GFP_ATOMIC - any node ok
+ * GFP_KERNEL - any node in enclosing mem_exclusive cpuset ok
+ * GFP_USER - only nodes in current tasks mems allowed ok.
+ **/
+
+int cpuset_zone_allowed(struct zone *z, unsigned int __nocast gfp_mask)
+{
+ int node; /* node that zone z is on */
+ const struct cpuset *cs; /* current cpuset ancestors */
+ int allowed = 1; /* is allocation in zone z allowed? */
+
+ if (in_interrupt())
+ return 1;
+ node = z->zone_pgdat->node_id;
+ if (node_isset(node, current->mems_allowed))
+ return 1;
+ if (gfp_mask & __GFP_HARDWALL) /* If hardwall request, stop here */
+ return 0;
+
+ /* Not hardwall and node outside mems_allowed: scan up cpusets */
+ cpuset_down(&cpuset_sem);
+ cs = current->cpuset;
+ if (!cs)
+ goto done; /* current task exiting */
+ cs = nearest_exclusive_ancestor(cs);
+ allowed = node_isset(node, cs->mems_allowed);
+done:
+ cpuset_up(&cpuset_sem);
+ return allowed;
+}
+
+/**
+ * cpuset_excl_nodes_overlap - Do we overlap @p's mem_exclusive ancestors?
+ * @p: pointer to task_struct of some other task.
+ *
+ * Description: Return true if the nearest mem_exclusive ancestor
+ * cpusets of tasks @p and current overlap. Used by oom killer to
+ * determine if task @p's memory usage might impact the memory
+ * available to the current task.
+ *
+ * Acquires cpuset_sem - not suitable for calling from a fast path.
+ **/
+
+int cpuset_excl_nodes_overlap(const struct task_struct *p)
{
- return in_interrupt() ||
- node_isset(z->zone_pgdat->node_id, current->mems_allowed);
+ const struct cpuset *cs1, *cs2; /* my and p's cpuset ancestors */
+ int overlap = 0; /* do cpusets overlap? */
+
+ cpuset_down(&cpuset_sem);
+ cs1 = current->cpuset;
+ if (!cs1)
+ goto done; /* current task exiting */
+ cs2 = p->cpuset;
+ if (!cs2)
+ goto done; /* task p is exiting */
+ cs1 = nearest_exclusive_ancestor(cs1);
+ cs2 = nearest_exclusive_ancestor(cs2);
+ overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
+done:
+ cpuset_up(&cpuset_sem);
+
+ return overlap;
}
/*
return -ENOMEM;
tsk = m->private;
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
task_lock(tsk);
cs = tsk->cpuset;
task_unlock(tsk);
seq_puts(m, buf);
seq_putc(m, '\n');
out:
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
kfree(buf);
return retval;
}
git.openpandora.org / pandora-kernel.git / blobdiff