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authorIan Campbell <ian.campbell@citrix.com>2009-12-17 13:57:09 +0000
committerIan Campbell <ian.campbell@citrix.com>2010-01-13 10:01:35 +0000
commitc5cae661d6cf808b6984762f763261adf35f3eb7 (patch)
tree0f19bd47b97b13421da7c0777ae5b1a87478e25c /drivers/xen
parent7284ce6c9f6153d1777df5f310c959724d1bd446 (diff)
xen: fix hang on suspend.
In 65f63384 "xen: improve error handling in do_suspend" I said: - xs_suspend()/xs_resume() and dpm_suspend_noirq()/dpm_resume_noirq() were not nested in the obvious way. and changed the ordering of the calls as so: BEFORE AFTER xs_suspend dpm_suspend_noirq dpm_suspend_noirq xs_suspend *SUSPEND* *SUSPEND* dpm_resume_noirq dpm_resume_noirq xs_resume xs_resume Clearly this is not an improvement and I was talking rubbish. In particular the new ordering is susceptible to a hang if a xenstore write is in progress at the point at which the suspend kicks in. When the suspend process calls xs_suspend it tries to take the request_mutex but if a write is in progress it could be looping in xenbus_xs.c:read_reply() waiting for something to arrive on &xs_state.reply_list while holding the request_mutex (taken in the caller of read_reply). However if we have done dpm_suspend_noirq before xs_suspend then we won't get any more xenstore interrupts and process_msg() will never be woken up to add anything to the reply_list. Fix this by calling xs_suspend before dpm_suspend_noirq. If dpm_suspend_noirq fails then make sure we go through the xs_suspend_cancel() code path. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Acked-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> Cc: Stable Kernel <stable@kernel.org>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/manage.c8
1 files changed, 4 insertions, 4 deletions
diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
index c4997930afc7..5d42d55e299b 100644
--- a/drivers/xen/manage.c
+++ b/drivers/xen/manage.c
@@ -102,15 +102,15 @@ static void do_suspend(void)
goto out_thaw;
}
+ printk(KERN_DEBUG "suspending xenstore...\n");
+ xs_suspend();
+
err = dpm_suspend_noirq(PMSG_SUSPEND);
if (err) {
printk(KERN_ERR "dpm_suspend_noirq failed: %d\n", err);
goto out_resume;
}
- printk(KERN_DEBUG "suspending xenstore...\n");
- xs_suspend();
-
err = stop_machine(xen_suspend, &cancelled, cpumask_of(0));
dpm_resume_noirq(PMSG_RESUME);
@@ -120,13 +120,13 @@ static void do_suspend(void)
cancelled = 1;
}
+out_resume:
if (!cancelled) {
xen_arch_resume();
xs_resume();
} else
xs_suspend_cancel();
-out_resume:
dpm_resume_end(PMSG_RESUME);
/* Make sure timer events get retriggered on all CPUs */