From 929423fa83e5b75e94101b280738b9a5a376a0e1 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Mon, 20 Jul 2015 13:49:39 +0200 Subject: xen: release lock occasionally during ballooning When dom0 is being ballooned balloon_process() will hold the balloon mutex until it is finished. This will block e.g. creation of new domains as the device backends for the new domain need some autoballooned pages for the ring buffers. Avoid this by releasing the balloon mutex from time to time during ballooning. Adjust the comment above balloon_process() regarding multiple instances of balloon_process(). Instead of open coding it, just use cond_resched(). Signed-off-by: Juergen Gross Signed-off-by: David Vrabel --- drivers/xen/balloon.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) (limited to 'drivers/xen') diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c index fd933695f232..bf4a23c7c591 100644 --- a/drivers/xen/balloon.c +++ b/drivers/xen/balloon.c @@ -472,7 +472,7 @@ static enum bp_state decrease_reservation(unsigned long nr_pages, gfp_t gfp) } /* - * We avoid multiple worker processes conflicting via the balloon mutex. + * As this is a work item 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. @@ -482,9 +482,10 @@ static void balloon_process(struct work_struct *work) enum bp_state state = BP_DONE; long credit; - mutex_lock(&balloon_mutex); do { + mutex_lock(&balloon_mutex); + credit = current_credit(); if (credit > 0) { @@ -499,17 +500,15 @@ static void balloon_process(struct work_struct *work) state = update_schedule(state); -#ifndef CONFIG_PREEMPT - if (need_resched()) - schedule(); -#endif + mutex_unlock(&balloon_mutex); + + cond_resched(); + } while (credit && state == BP_DONE); /* Schedule more work if there is some still to be done. */ if (state == BP_EAGAIN) schedule_delayed_work(&balloon_worker, balloon_stats.schedule_delay * HZ); - - mutex_unlock(&balloon_mutex); } /* Resets the Xen limit, sets new target, and kicks off processing. */ -- cgit v1.2.3