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xen: Fix XenStore initialisation for XS_LOCAL 

In commit 3499ba8198 ("xen: Fix event channel callback via INTX/GSI")
I reworked the triggering of xenbus_probe().

I tried to simplify things by taking out the workqueue based startup
triggered from wake_waiting(); the somewhat poorly named xenbus IRQ
handler.

I missed the fact that in the XS_LOCAL case (Dom0 starting its own
xenstored or xenstore-stubdom, which happens after the kernel is booted
completely), that IRQ-based trigger is still actually needed.

So... put it back, except more cleanly. By just spawning a xenbus_probe
thread which waits on xb_waitq and runs the probe the first time it
gets woken, just as the workqueue-based hack did.

This is actually a nicer approach for *all* the back ends with different
interrupt methods, and we can switch them all over to that without the
complex conditions for when to trigger it. But not in -rc6. This is
the minimal fix for the regression, although it's a step in the right
direction instead of doing a partial revert and actually putting the
workqueue back. It's also simpler than the workqueue.

Fixes: 3499ba8198 ("xen: Fix event channel callback via INTX/GSI")
Reported-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/4c9af052a6e0f6485d1de43f2c38b1461996db99.camel@infradead.org
Signed-off-by: Juergen Gross <jgross@suse.com>
master
David Woodhouse 2021-01-26 17:01:49 +00:00 committed by Juergen Gross
parent 0549cd67b0
commit 5f46400f7a
1 changed files with 31 additions and 0 deletions
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31
drivers/xen/xenbus/xenbus_probe.c
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@ -714,6 +714,23 @@ static bool xs_hvm_defer_init_for_callback(void)
#endif
}
static int xenbus_probe_thread(void *unused)
{
DEFINE_WAIT(w);
/*
* We actually just want to wait for *any* trigger of xb_waitq,
* and run xenbus_probe() the moment it occurs.
*/
prepare_to_wait(&xb_waitq, &w, TASK_INTERRUPTIBLE);
schedule();
finish_wait(&xb_waitq, &w);
DPRINTK("probing");
xenbus_probe();
return 0;
}
static int __init xenbus_probe_initcall(void)
{
/*
@ -725,6 +742,20 @@ static int __init xenbus_probe_initcall(void)
!xs_hvm_defer_init_for_callback()))
xenbus_probe();
/*
* For XS_LOCAL, spawn a thread which will wait for xenstored
* or a xenstore-stubdom to be started, then probe. It will be
* triggered when communication starts happening, by waiting
* on xb_waitq.
*/
if (xen_store_domain_type == XS_LOCAL) {
struct task_struct *probe_task;
probe_task = kthread_run(xenbus_probe_thread, NULL,
"xenbus_probe");
if (IS_ERR(probe_task))
return PTR_ERR(probe_task);
}
return 0;
}
device_initcall(xenbus_probe_initcall);