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-rw-r--r--kernel/cpuset.c100
1 files changed, 60 insertions, 40 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 712d0202997..407b5f0a8c8 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -182,6 +182,37 @@ static struct super_block *cpuset_sb = NULL;
static DECLARE_MUTEX(cpuset_sem);
/*
+ * 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 (current->cpuset_sem_nest_depth == 0)
+ down(psem);
+ current->cpuset_sem_nest_depth++;
+}
+
+static inline void cpuset_up(struct semaphore *psem)
+{
+ current->cpuset_sem_nest_depth--;
+ if (current->cpuset_sem_nest_depth == 0)
+ up(psem);
+}
+
+/*
* A couple of forward declarations required, due to cyclic reference loop:
* cpuset_mkdir -> cpuset_create -> cpuset_populate_dir -> cpuset_add_file
* -> cpuset_create_file -> cpuset_dir_inode_operations -> cpuset_mkdir.
@@ -522,19 +553,10 @@ static void guarantee_online_mems(const struct cpuset *cs, nodemask_t *pmask)
* 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)
@@ -840,7 +862,7 @@ static ssize_t cpuset_common_file_write(struct file *file, const char __user *us
}
buffer[nbytes] = 0; /* nul-terminate */
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
if (is_removed(cs)) {
retval = -ENODEV;
@@ -874,7 +896,7 @@ static ssize_t cpuset_common_file_write(struct file *file, const char __user *us
if (retval == 0)
retval = nbytes;
out2:
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
cpuset_release_agent(pathbuf);
out1:
kfree(buffer);
@@ -914,9 +936,9 @@ static int cpuset_sprintf_cpulist(char *page, struct cpuset *cs)
{
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);
}
@@ -925,9 +947,9 @@ static int cpuset_sprintf_memlist(char *page, struct cpuset *cs)
{
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);
}
@@ -1334,8 +1356,7 @@ static long cpuset_create(struct cpuset *parent, const char *name, int mode)
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);
@@ -1360,14 +1381,14 @@ static long cpuset_create(struct cpuset *parent, const char *name, int mode)
* 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;
}
@@ -1389,14 +1410,13 @@ static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry)
/* 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;
@@ -1412,7 +1432,7 @@ static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry)
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;
}
@@ -1515,10 +1535,10 @@ void cpuset_exit(struct task_struct *tsk)
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);
@@ -1539,11 +1559,11 @@ cpumask_t cpuset_cpus_allowed(const struct task_struct *tsk)
{
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;
}
@@ -1568,9 +1588,9 @@ void cpuset_update_current_mems_allowed(void)
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);
}
}
@@ -1669,14 +1689,14 @@ int cpuset_zone_allowed(struct zone *z, unsigned int __nocast gfp_mask)
return 0;
/* Not hardwall and node outside mems_allowed: scan up cpusets */
- down(&cpuset_sem);
+ 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:
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
return allowed;
}
@@ -1697,7 +1717,7 @@ int cpuset_excl_nodes_overlap(const struct task_struct *p)
const struct cpuset *cs1, *cs2; /* my and p's cpuset ancestors */
int overlap = 0; /* do cpusets overlap? */
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
cs1 = current->cpuset;
if (!cs1)
goto done; /* current task exiting */
@@ -1708,7 +1728,7 @@ int cpuset_excl_nodes_overlap(const struct task_struct *p)
cs2 = nearest_exclusive_ancestor(cs2);
overlap = nodes_intersects(cs1->mems_allowed, cs2->mems_allowed);
done:
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
return overlap;
}
@@ -1731,7 +1751,7 @@ static int proc_cpuset_show(struct seq_file *m, void *v)
return -ENOMEM;
tsk = m->private;
- down(&cpuset_sem);
+ cpuset_down(&cpuset_sem);
task_lock(tsk);
cs = tsk->cpuset;
task_unlock(tsk);
@@ -1746,7 +1766,7 @@ static int proc_cpuset_show(struct seq_file *m, void *v)
seq_puts(m, buf);
seq_putc(m, '\n');
out:
- up(&cpuset_sem);
+ cpuset_up(&cpuset_sem);
kfree(buf);
return retval;
}
generated by cgit v1.2.3-70-g09d2 (git 2.46.0) at 2024-11-27 14:41:17 +0000