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Subject[PATCH] kernel/rcupdate.c microcleanup
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Hi all,

attached patch (2.5.64) contains small cleanup of RCU code:
- move smp_processor_id() outside of irq disabled region in call_rcu();
- consolidate multiple spin_unlock() in the rcu_check_quiescent_state(),
remove some unneeded {} and make this function inline.

Tested and works (at least doesn't crash). Please consider applying.

Best regards.

--
Andrey Panin | Embedded systems software developer
pazke@orbita1.ru | PGP key: wwwkeys.pgp.net
diff -urN -X /usr/share/dontdiff linux-2.5.64.vanilla/kernel/rcupdate.c linux-2.5.64/kernel/rcupdate.c
--- linux-2.5.64.vanilla/kernel/rcupdate.c Thu Nov 28 01:35:46 2002
+++ linux-2.5.64/kernel/rcupdate.c Mon Mar 10 20:18:48 2003
@@ -67,13 +67,12 @@
*/
void call_rcu(struct rcu_head *head, void (*func)(void *arg), void *arg)
{
- int cpu;
+ int cpu = smp_processor_id();
unsigned long flags;

head->func = func;
head->arg = arg;
local_irq_save(flags);
- cpu = smp_processor_id();
list_add_tail(&head->list, &RCU_nxtlist(cpu));
local_irq_restore(flags);
}
@@ -117,13 +116,12 @@
* switch). If so and if it already hasn't done so in this RCU
* quiescent cycle, then indicate that it has done so.
*/
-static void rcu_check_quiescent_state(void)
+static inline void rcu_check_quiescent_state(void)
{
int cpu = smp_processor_id();

- if (!test_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask)) {
+ if (!test_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask))
return;
- }

/*
* Races with local timer interrupt - in the worst case
@@ -134,23 +132,22 @@
RCU_last_qsctr(cpu) = RCU_qsctr(cpu);
return;
}
- if (RCU_qsctr(cpu) == RCU_last_qsctr(cpu)) {
+ if (RCU_qsctr(cpu) == RCU_last_qsctr(cpu))
return;
- }

spin_lock(&rcu_ctrlblk.mutex);
- if (!test_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask)) {
- spin_unlock(&rcu_ctrlblk.mutex);
- return;
- }
+ if (!test_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask))
+ goto out_unlock;
+
clear_bit(cpu, &rcu_ctrlblk.rcu_cpu_mask);
RCU_last_qsctr(cpu) = RCU_QSCTR_INVALID;
- if (rcu_ctrlblk.rcu_cpu_mask != 0) {
- spin_unlock(&rcu_ctrlblk.mutex);
- return;
- }
+ if (rcu_ctrlblk.rcu_cpu_mask != 0)
+ goto out_unlock;
+
rcu_ctrlblk.curbatch++;
rcu_start_batch(rcu_ctrlblk.maxbatch);
+
+out_unlock:
spin_unlock(&rcu_ctrlblk.mutex);
}
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