Re: [PATCH 1/4] comm: Introduce comm_lock spinlock to protect task->comm access
From: KOSAKI Motohiro <hidden>
Date: 2011-05-18 02:01:47
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lkml
quoted hunk ↗ jump to hunk
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.
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