Messages in this thread | | | Date | Wed, 18 May 2011 11:01:30 +0900 | From | KOSAKI Motohiro <> | Subject | Re: [PATCH 1/4] comm: Introduce comm_lock spinlock to protect task->comm access |
| |
> diff --git a/fs/exec.c b/fs/exec.c > index 5e62d26..34fa611 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -998,17 +998,28 @@ static void flush_old_files(struct files_struct * files) > > char *get_task_comm(char *buf, struct task_struct *tsk) > { > - /* buf must be at least sizeof(tsk->comm) in size */ > - task_lock(tsk); > + unsigned long flags; > + > + spin_lock_irqsave(&tsk->comm_lock, flags); > strncpy(buf, tsk->comm, sizeof(tsk->comm)); > - task_unlock(tsk); > + spin_unlock_irqrestore(&tsk->comm_lock, flags); > return buf; > } > > void set_task_comm(struct task_struct *tsk, char *buf) > { > + unsigned long flags; > + > + /* > + * XXX - Even though comm is protected by comm_lock, > + * we take the task_lock here to serialize against > + * current users that directly access comm. > + * Once those users are removed, we can drop the > + * task locking& memsetting. > + */
If we provide __get_task_comm(), we can't remove memset() forever.
> task_lock(tsk); > + spin_lock_irqsave(&tsk->comm_lock, flags);
This is strange order. task_lock() doesn't disable interrupt. And, can you please document why we need interrupt disabling?
> /* > * Threads may access current->comm without holding > * the task lock, so write the string carefully.
| |