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SUNRPC: Fix a potential race in rpc_wake_up_task()

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Use RCU to ensure that we can safely call rpc_finish_wakeup after we've
called __rpc_do_wake_up_task. If not, there is a theoretical race, in which
the rpc_task finishes executing, and gets freed first.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Trond Myklebust
2006-11-13 16:23:44 -05:00
parent e6b3c4db6f
commit 8aca67f0ae
5 changed files with 47 additions and 20 deletions
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30
net/sunrpc/sched.c
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@@ -427,16 +427,19 @@ __rpc_default_timer(struct rpc_task *task)
*/
void rpc_wake_up_task(struct rpc_task *task)
{
rcu_read_lock_bh();
if (rpc_start_wakeup(task)) {
if (RPC_IS_QUEUED(task)) {
struct rpc_wait_queue *queue = task->u.tk_wait.rpc_waitq;
spin_lock_bh(&queue->lock);
/* Note: we're already in a bh-safe context */
spin_lock(&queue->lock);
__rpc_do_wake_up_task(task);
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
}
rpc_finish_wakeup(task);
}
rcu_read_unlock_bh();
}
/*
@@ -499,14 +502,16 @@ struct rpc_task * rpc_wake_up_next(struct rpc_wait_queue *queue)
struct rpc_task *task = NULL;
dprintk("RPC: wake_up_next(%p \"%s\")\n", queue, rpc_qname(queue));
spin_lock_bh(&queue->lock);
rcu_read_lock_bh();
spin_lock(&queue->lock);
if (RPC_IS_PRIORITY(queue))
task = __rpc_wake_up_next_priority(queue);
else {
task_for_first(task, &queue->tasks[0])
__rpc_wake_up_task(task);
}
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
rcu_read_unlock_bh();
return task;
}
@@ -522,7 +527,8 @@ void rpc_wake_up(struct rpc_wait_queue *queue)
struct rpc_task *task, *next;
struct list_head *head;
spin_lock_bh(&queue->lock);
rcu_read_lock_bh();
spin_lock(&queue->lock);
head = &queue->tasks[queue->maxpriority];
for (;;) {
list_for_each_entry_safe(task, next, head, u.tk_wait.list)
@@ -531,7 +537,8 @@ void rpc_wake_up(struct rpc_wait_queue *queue)
break;
head--;
}
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
rcu_read_unlock_bh();
}
/**
@@ -546,7 +553,8 @@ void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
struct rpc_task *task, *next;
struct list_head *head;
spin_lock_bh(&queue->lock);
rcu_read_lock_bh();
spin_lock(&queue->lock);
head = &queue->tasks[queue->maxpriority];
for (;;) {
list_for_each_entry_safe(task, next, head, u.tk_wait.list) {
@@ -557,7 +565,8 @@ void rpc_wake_up_status(struct rpc_wait_queue *queue, int status)
break;
head--;
}
spin_unlock_bh(&queue->lock);
spin_unlock(&queue->lock);
rcu_read_unlock_bh();
}
static void __rpc_atrun(struct rpc_task *task)
@@ -817,8 +826,9 @@ rpc_alloc_task(void)
return (struct rpc_task *)mempool_alloc(rpc_task_mempool, GFP_NOFS);
}
static void rpc_free_task(struct rpc_task *task)
static void rpc_free_task(struct rcu_head *rcu)
{
struct rpc_task *task = container_of(rcu, struct rpc_task, u.tk_rcu);
dprintk("RPC: %4d freeing task\n", task->tk_pid);
mempool_free(task, rpc_task_mempool);
}
@@ -872,7 +882,7 @@ void rpc_put_task(struct rpc_task *task)
task->tk_client = NULL;
}
if (task->tk_flags & RPC_TASK_DYNAMIC)
rpc_free_task(task);
call_rcu_bh(&task->u.tk_rcu, rpc_free_task);
if (tk_ops->rpc_release)
tk_ops->rpc_release(calldata);
}