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rcu: Clarify rcu_is_watching() kernel-doc comment

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Make it clear that this function always returns either true or false
without other planned failure modes.

Reported-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
This commit is contained in:
Paul E. McKenney 2023-05-23 02:22:10 -07:00
parent 6716f4d39c
commit c924bf5a43
1 changed files with 9 additions and 5 deletions
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14
kernel/rcu/tree.c
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@ -677,12 +677,16 @@ static void rcu_disable_urgency_upon_qs(struct rcu_data *rdp)
}
/**
* rcu_is_watching - see if RCU thinks that the current CPU is not idle
* rcu_is_watching - RCU read-side critical sections permitted on current CPU?
*
* Return true if RCU is watching the running CPU, which means that this
* CPU can safely enter RCU read-side critical sections. In other words,
* if the current CPU is not in its idle loop or is in an interrupt or
* NMI handler, return true.
* Return @true if RCU is watching the running CPU and @false otherwise.
* An @true return means that this CPU can safely enter RCU read-side
* critical sections.
*
* Although calls to rcu_is_watching() from most parts of the kernel
* will return @true, there are important exceptions. For example, if the
* current CPU is deep within its idle loop, in kernel entry/exit code,
* or offline, rcu_is_watching() will return @false.
*
* Make notrace because it can be called by the internal functions of
* ftrace, and making this notrace removes unnecessary recursion calls.