On 08.09.21 16:47, Boris Ostrovsky wrote:
On 8/27/21 8:32 AM, Juergen Gross wrote:+static bool balloon_thread_cond(enum bp_state state, long credit) +{ + if (state != BP_EAGAIN) + credit = 0; + + return current_credit() != credit || kthread_should_stop(); +} + +/* + * As this is a kthread it is guaranteed to run as a single instance only. * We may of course race updates of the target counts (which are protected * by the balloon lock), or with changes to the Xen hard limit, but we will * recover from these in time. */ -static void balloon_process(struct work_struct *work) +static int balloon_thread(void *unused) { enum bp_state state = BP_DONE; long credit; + unsigned long timeout; + + set_freezable(); + for (;;) { + if (state == BP_EAGAIN) + timeout = balloon_stats.schedule_delay * HZ; + else + timeout = 3600 * HZ; + credit = current_credit();+ wait_event_interruptible_timeout(balloon_thread_wq,+ balloon_thread_cond(state, credit), timeout);Given that wait_event_interruptible_timeout() is a bunch of nested macros do we need to worry here about overly aggressive compiler optimizing out 'credit = current_credit()'?
I don't think so. current_credit() is reading from balloon_stats, which is a global variable. So the compiler shouldn't assume the contents won't change. But I can add a barrier() after 'credit = current_credit()' in case you'd feel uneasy without it. Juergen
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