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signals: Fix more rcu assumptions
1) Remove the misleading comment in __sigqueue_alloc() which claims that holding a spinlock is equivalent to rcu_read_lock(). 2) Add a rcu_read_lock/unlock around the __task_cred() access in __sigqueue_alloc() This needs to be revisited to remove the remaining users of read_lock(&tasklist_lock) but that's outside the scope of this patch. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> LKML-Reference: <20091210004703.269843657@linutronix.de>
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@ -218,13 +218,13 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t flags, int override_rlimi
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struct user_struct *user;
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/*
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* We won't get problems with the target's UID changing under us
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* because changing it requires RCU be used, and if t != current, the
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* caller must be holding the RCU readlock (by way of a spinlock) and
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* we use RCU protection here
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* Protect access to @t credentials. This can go away when all
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* callers hold rcu read lock.
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*/
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rcu_read_lock();
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user = get_uid(__task_cred(t)->user);
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atomic_inc(&user->sigpending);
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rcu_read_unlock();
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if (override_rlimit ||
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atomic_read(&user->sigpending) <=
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