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Commit c7037ff5 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Clarify and correct the rcu_preempt_qs() header comment 



The rcu_preempt_qs() function only applies to the CPU, not the task.
A task really is allowed to invoke this function while in an RCU-preempt
read-side critical section, but only if it has first added itself to
some leaf rcu_node structure's ->blkd_tasks list.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 3b57a399

kernel/rcu/tree_plugin.h

+10 −6
Original line number Diff line number Diff line
@@ -294,13 +294,17 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp) 
}



/*

 * Record a preemptible-RCU quiescent state for the specified CPU.  Note

 * that this just means that the task currently running on the CPU is

 * not in a quiescent state.  There might be any number of tasks blocked

 * while in an RCU read-side critical section.

 * Record a preemptible-RCU quiescent state for the specified CPU.

 * Note that this does not necessarily mean that the task currently running

 * on the CPU is in a quiescent state:  Instead, it means that the current

 * grace period need not wait on any RCU read-side critical section that

 * starts later on this CPU.  It also means that if the current task is

 * in an RCU read-side critical section, it has already added itself to

 * some leaf rcu_node structure's ->blkd_tasks list.  In addition to the

 * current task, there might be any number of other tasks blocked while

 * in an RCU read-side critical section.

 *

 * As with the other rcu_*_qs() functions, callers to this function

 * must disable preemption.

 * Callers to this function must disable preemption.

 */

static void rcu_preempt_qs(void)

{