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rcu: Remove now-unused ->b.exp_need_qs field from the rcu_special union

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The ->b.exp_need_qs field is now set only to false, so this commit
removes it.  The job this field used to do is now done by the rcu_data
structure's ->deferred_qs field, which is a consequence of a better
split between task-based (the rcu_node structure's ->exp_tasks field) and
CPU-based (the aforementioned rcu_data structure's ->deferred_qs field)
tracking of quiescent states for RCU-preempt expedited grace periods.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-06-28 07:39:59 -07:00
parent 27c744e32a
commit fcc878e4df
2 changed files with 5 additions and 14 deletions
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6
include/linux/sched.h
View File

@ -571,12 +571,8 @@ union rcu_special {
struct {
u8 blocked;
u8 need_qs;
u8 exp_need_qs;
/* Otherwise the compiler can store garbage here: */
u8 pad;
} b; /* Bits. */
u32 s; /* Set of bits. */
u16 s; /* Set of bits. */
};
enum perf_event_task_context {

13
kernel/rcu/tree_plugin.h
View File

@ -284,13 +284,10 @@ static void rcu_preempt_ctxt_queue(struct rcu_node *rnp, struct rcu_data *rdp)
* no need to check for a subsequent expedited GP. (Though we are
* still in a quiescent state in any case.)
*/
if (blkd_state & RCU_EXP_BLKD &&
t->rcu_read_unlock_special.b.exp_need_qs) {
t->rcu_read_unlock_special.b.exp_need_qs = false;
if (blkd_state & RCU_EXP_BLKD && rdp->deferred_qs)
rcu_report_exp_rdp(rdp->rsp, rdp, true);
} else {
WARN_ON_ONCE(t->rcu_read_unlock_special.b.exp_need_qs);
}
else
WARN_ON_ONCE(rdp->deferred_qs);
}
/*
@ -509,9 +506,7 @@ rcu_preempt_deferred_qs_irqrestore(struct task_struct *t, unsigned long flags)
* tasks are handled when removing the task from the
* blocked-tasks list below.
*/
if (special.b.exp_need_qs || rdp->deferred_qs) {
t->rcu_read_unlock_special.b.exp_need_qs = false;
rdp->deferred_qs = false;
if (rdp->deferred_qs) {
rcu_report_exp_rdp(rcu_state_p, rdp, true);
if (!t->rcu_read_unlock_special.s) {
local_irq_restore(flags);