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rcu/tree: Remove CONFIG_PREMPT_RCU check in force_qs_rnp() 

Originally, the call to rcu_preempt_blocked_readers_cgp() from
force_qs_rnp() had to be conditioned on CONFIG_PREEMPT_RCU=y, as in
commit a77da14ce9 ("rcu: Yet another fix for preemption and CPU
hotplug").  However, there is now a CONFIG_PREEMPT_RCU=n definition of
rcu_preempt_blocked_readers_cgp() that unconditionally returns zero, so
invoking it is now safe.  In addition, the CONFIG_PREEMPT_RCU=n definition
of rcu_initiate_boost() simply releases the rcu_node structure's ->lock,
which is what happens when the "if" condition evaluates to false.

This commit therefore drops the IS_ENABLED(CONFIG_PREEMPT_RCU) check,
so that rcu_initiate_boost() is called only in CONFIG_PREEMPT_RCU=y
kernels when there are readers blocking the current grace period.
This does not change the behavior, but reduces code-reader confusion by
eliminating non-CONFIG_PREEMPT_RCU=y calls to rcu_initiate_boost().

Signed-off-by: Neeraj Upadhyay <neeraju@codeaurora.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Neeraj Upadhyay 2020-06-22 23:37:03 +05:30 committed by Paul E. McKenney
parent 9c39245382
commit 9b1ce0acb5
1 changed files with 1 additions and 2 deletions
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3
kernel/rcu/tree.c
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@ -2533,8 +2533,7 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp))
raw_spin_lock_irqsave_rcu_node(rnp, flags);
rcu_state.cbovldnext |= !!rnp->cbovldmask;
if (rnp->qsmask == 0) {
if (!IS_ENABLED(CONFIG_PREEMPT_RCU) ||
rcu_preempt_blocked_readers_cgp(rnp)) {
if (rcu_preempt_blocked_readers_cgp(rnp)) {
/*
* No point in scanning bits because they
* are all zero. But we might need to