diff options
| -rw-r--r-- | kernel/cpuset.c | 105 |
1 files changed, 40 insertions, 65 deletions
diff --git a/kernel/cpuset.c b/kernel/cpuset.c index b9342f90d28f..cd54dba2be18 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -180,42 +180,6 @@ static struct super_block *cpuset_sb = NULL; */ 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: @@ -558,10 +522,19 @@ 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. * - * 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. + * 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. */ static void refresh_mems(void) @@ -867,7 +840,7 @@ static ssize_t cpuset_common_file_write(struct file *file, const char __user *us } buffer[nbytes] = 0; /* nul-terminate */ - cpuset_down(&cpuset_sem); + down(&cpuset_sem); if (is_removed(cs)) { retval = -ENODEV; @@ -901,7 +874,7 @@ static ssize_t cpuset_common_file_write(struct file *file, const char __user *us if (retval == 0) retval = nbytes; out2: - cpuset_up(&cpuset_sem); + up(&cpuset_sem); cpuset_release_agent(pathbuf); out1: kfree(buffer); @@ -941,9 +914,9 @@ static int cpuset_sprintf_cpulist(char *page, struct cpuset *cs) { cpumask_t mask; - cpuset_down(&cpuset_sem); + down(&cpuset_sem); mask = cs->cpus_allowed; - cpuset_up(&cpuset_sem); + up(&cpuset_sem); return cpulist_scnprintf(page, PAGE_SIZE, mask); } @@ -952,9 +925,9 @@ static int cpuset_sprintf_memlist(char *page, struct cpuset *cs) { nodemask_t mask; - cpuset_down(&cpuset_sem); + down(&cpuset_sem); mask = cs->mems_allowed; - cpuset_up(&cpuset_sem); + up(&cpuset_sem); return nodelist_scnprintf(page, PAGE_SIZE, mask); } @@ -1351,7 +1324,8 @@ static long cpuset_create(struct cpuset *parent, const char *name, int mode) if (!cs) return -ENOMEM; - cpuset_down(&cpuset_sem); + down(&cpuset_sem); + refresh_mems(); cs->flags = 0; if (notify_on_release(parent)) set_bit(CS_NOTIFY_ON_RELEASE, &cs->flags); @@ -1376,14 +1350,14 @@ 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. */ - cpuset_up(&cpuset_sem); + 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); - cpuset_up(&cpuset_sem); + up(&cpuset_sem); kfree(cs); return err; } @@ -1405,13 +1379,14 @@ static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry) /* the vfs holds both inode->i_sem already */ - cpuset_down(&cpuset_sem); + down(&cpuset_sem); + refresh_mems(); if (atomic_read(&cs->count) > 0) { - cpuset_up(&cpuset_sem); + up(&cpuset_sem); return -EBUSY; } if (!list_empty(&cs->children)) { - cpuset_up(&cpuset_sem); + up(&cpuset_sem); return -EBUSY; } parent = cs->parent; @@ -1427,7 +1402,7 @@ static int cpuset_rmdir(struct inode *unused_dir, struct dentry *dentry) spin_unlock(&d->d_lock); cpuset_d_remove_dir(d); dput(d); - cpuset_up(&cpuset_sem); + up(&cpuset_sem); cpuset_release_agent(pathbuf); return 0; } @@ -1530,10 +1505,10 @@ void cpuset_exit(struct task_struct *tsk) if (notify_on_release(cs)) { char *pathbuf = NULL; - cpuset_down(&cpuset_sem); + down(&cpuset_sem); if (atomic_dec_and_test(&cs->count)) check_for_release(cs, &pathbuf); - cpuset_up(&cpuset_sem); + up(&cpuset_sem); cpuset_release_agent(pathbuf); } else { atomic_dec(&cs->count); @@ -1554,11 +1529,11 @@ cpumask_t cpuset_cpus_allowed(const struct task_struct *tsk) { cpumask_t mask; - cpuset_down(&cpuset_sem); + down(&cpuset_sem); task_lock((struct task_struct *)tsk); guarantee_online_cpus(tsk->cpuset, &mask); task_unlock((struct task_struct *)tsk); - cpuset_up(&cpuset_sem); + up(&cpuset_sem); return mask; } @@ -1583,9 +1558,9 @@ void cpuset_update_current_mems_allowed(void) if (!cs) return; /* task is exiting */ if (current->cpuset_mems_generation != cs->mems_generation) { - cpuset_down(&cpuset_sem); + down(&cpuset_sem); refresh_mems(); - cpuset_up(&cpuset_sem); + up(&cpuset_sem); } } @@ -1684,14 +1659,14 @@ int cpuset_zone_allowed(struct zone *z, gfp_t gfp_mask) return 0; /* Not hardwall and node outside mems_allowed: scan up cpusets */ - cpuset_down(&cpuset_sem); + 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); + up(&cpuset_sem); return allowed; } @@ -1712,7 +1687,7 @@ 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? */ - cpuset_down(&cpuset_sem); + down(&cpuset_sem); cs1 = current->cpuset; if (!cs1) goto done; /* current task exiting */ @@ -1723,7 +1698,7 @@ 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: - cpuset_up(&cpuset_sem); + up(&cpuset_sem); return overlap; } @@ -1746,7 +1721,7 @@ static int proc_cpuset_show(struct seq_file *m, void *v) return -ENOMEM; tsk = m->private; - cpuset_down(&cpuset_sem); + down(&cpuset_sem); task_lock(tsk); cs = tsk->cpuset; task_unlock(tsk); @@ -1761,7 +1736,7 @@ static int proc_cpuset_show(struct seq_file *m, void *v) seq_puts(m, buf); seq_putc(m, '\n'); out: - cpuset_up(&cpuset_sem); + up(&cpuset_sem); kfree(buf); return retval; } |