*/
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:
* to continue to serve a useful existence. Next time it's released,
* we will get notified again, if it still has 'notify_on_release' set.
*
- * Note final arg to call_usermodehelper() is 0 - that means
- * don't wait. Since we are holding the global cpuset_sem here,
- * and we are asking another thread (started from keventd) to rmdir a
- * cpuset, we can't wait - or we'd deadlock with the removing thread
- * on cpuset_sem.
+ * The final arg to call_usermodehelper() is 0, which means don't
+ * wait. The separate /sbin/cpuset_release_agent task is forked by
+ * call_usermodehelper(), then control in this thread returns here,
+ * without waiting for the release agent task. We don't bother to
+ * wait because the caller of this routine has no use for the exit
+ * status of the /sbin/cpuset_release_agent task, so no sense holding
+ * our caller up for that.
+ *
+ * The simple act of forking that task might require more memory,
+ * which might need cpuset_sem. So this routine must be called while
+ * cpuset_sem is not held, to avoid a possible deadlock. See also
+ * comments for check_for_release(), below.
*/
-static int cpuset_release_agent(char *cpuset_str)
+static void cpuset_release_agent(const char *pathbuf)
{
char *argv[3], *envp[3];
int i;
+ if (!pathbuf)
+ return;
+
i = 0;
argv[i++] = "/sbin/cpuset_release_agent";
- argv[i++] = cpuset_str;
+ argv[i++] = (char *)pathbuf;
argv[i] = NULL;
i = 0;
envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
envp[i] = NULL;
- return call_usermodehelper(argv[0], argv, envp, 0);
+ call_usermodehelper(argv[0], argv, envp, 0);
+ kfree(pathbuf);
}
/*
* Either cs->count of using tasks transitioned to zero, or the
* cs->children list of child cpusets just became empty. If this
* cs is notify_on_release() and now both the user count is zero and
- * the list of children is empty, send notice to user land.
+ * the list of children is empty, prepare cpuset path in a kmalloc'd
+ * buffer, to be returned via ppathbuf, so that the caller can invoke
+ * cpuset_release_agent() with it later on, once cpuset_sem is dropped.
+ * Call here with cpuset_sem held.
+ *
+ * This check_for_release() routine is responsible for kmalloc'ing
+ * pathbuf. The above cpuset_release_agent() is responsible for
+ * kfree'ing pathbuf. The caller of these routines is responsible
+ * for providing a pathbuf pointer, initialized to NULL, then
+ * calling check_for_release() with cpuset_sem held and the address
+ * of the pathbuf pointer, then dropping cpuset_sem, then calling
+ * cpuset_release_agent() with pathbuf, as set by check_for_release().
*/
-static void check_for_release(struct cpuset *cs)
+static void check_for_release(struct cpuset *cs, char **ppathbuf)
{
if (notify_on_release(cs) && atomic_read(&cs->count) == 0 &&
list_empty(&cs->children)) {
if (!buf)
return;
if (cpuset_path(cs, buf, PAGE_SIZE) < 0)
- goto out;
- cpuset_release_agent(buf);
-out:
- kfree(buf);
+ kfree(buf);
+ else
+ *ppathbuf = buf;
}
}
* 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;
return 0;
}
-static int attach_task(struct cpuset *cs, char *buf)
+static int attach_task(struct cpuset *cs, char *pidbuf, char **ppathbuf)
{
pid_t pid;
struct task_struct *tsk;
struct cpuset *oldcs;
cpumask_t cpus;
- if (sscanf(buf, "%d", &pid) != 1)
+ if (sscanf(pidbuf, "%d", &pid) != 1)
return -EIO;
if (cpus_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
return -ENOSPC;
put_task_struct(tsk);
if (atomic_dec_and_test(&oldcs->count))
- check_for_release(oldcs);
+ check_for_release(oldcs, ppathbuf);
return 0;
}
struct cftype *cft = __d_cft(file->f_dentry);
cpuset_filetype_t type = cft->private;
char *buffer;
+ char *pathbuf = NULL;
int retval = 0;
/* Crude upper limit on largest legitimate cpulist user might write. */
}
buffer[nbytes] = 0; /* nul-terminate */
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
if (is_removed(cs)) {
retval = -ENODEV;
retval = update_flag(CS_NOTIFY_ON_RELEASE, cs, buffer);
break;
case FILE_TASKLIST:
- retval = attach_task(cs, buffer);
+ retval = attach_task(cs, buffer, &pathbuf);
break;
default:
retval = -EINVAL;
if (retval == 0)
retval = nbytes;
out2:
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
+ cpuset_release_agent(pathbuf);
out1:
kfree(buffer);
return retval;
{
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);
}
char *page;
ssize_t retval = 0;
char *s;
- char *start;
- size_t n;
if (!(page = (char *)__get_free_page(GFP_KERNEL)))
return -ENOMEM;
*s++ = '\n';
*s = '\0';
- start = page + *ppos;
- n = s - start;
- retval = n - copy_to_user(buf, start, min(n, nbytes));
- *ppos += retval;
+ retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page);
out:
free_page((unsigned long)page);
return retval;
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;
}
struct cpuset *cs = dentry->d_fsdata;
struct dentry *d;
struct cpuset *parent;
+ char *pathbuf = NULL;
/* 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;
update_cpu_domains(cs);
list_del(&cs->sibling); /* delete my sibling from parent->children */
if (list_empty(&parent->children))
- check_for_release(parent);
+ check_for_release(parent, &pathbuf);
spin_lock(&cs->dentry->d_lock);
d = dget(cs->dentry);
cs->dentry = NULL;
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;
}
task_unlock(tsk);
if (notify_on_release(cs)) {
- down(&cpuset_sem);
+ char *pathbuf = NULL;
+
+ cpuset_down(&cpuset_sem);
if (atomic_dec_and_test(&cs->count))
- check_for_release(cs);
- up(&cpuset_sem);
+ check_for_release(cs, &pathbuf);
+ 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, gfp_t 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;
}
projects / linux-2.6 / blobdiff