I know that an integer variable should be declared volatile to share between
CPUs.
But for more complicated variable, I don't know if it should be volatile.
for example:
linux-2.6.6/kernel/workqueue.c:
struct workqueue_struct *__create_workqueue(const char *name,int
singlethread)
{
...
if (singlethread) {
...
} else {
spin_lock(&workqueue_lock);
list_add(&wq->list, &workqueues);
spin_unlock_irq(&workqueue_lock);
...
}
...
}
workqueues is a none volatile list_head. The spin_lock/unlock act as memory
barrier, so gcc flush any register cached value to memory. But if another
CPU allocate workqueues.next/prev in registers, how to make sure this cpu
get new value ?
static int __devinit workqueue_cpu_callback(struct notifier_block *nfb,
unsigned long action,
void *hcpu)
{
...
switch (action) {
case CPU_UP_PREPARE:
/* Create a new workqueue thread for it. */
list_for_each_entry(wq, &workqueues, list) {
...
}
how to make sure workqueue_cpu_callback() get new value ?
thanks very much
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