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authorDavid Woodhouse <dwmw@amazon.co.uk>2021-01-26 17:01:49 +0000
committerJuergen Gross <jgross@suse.com>2021-01-27 08:59:52 +0100
commit5f46400f7a6a4fad635d5a79e2aa5a04a30ffea1 (patch)
tree85b377d2b16d13a0b5d6583fa3ec14a908afa16c /drivers/xen
parent0549cd67b01016b579047bce045b386202a8bcfc (diff)
xen: Fix XenStore initialisation for XS_LOCAL
In commit 3499ba8198ca ("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: 3499ba8198ca ("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>
Diffstat (limited to 'drivers/xen')
-rw-r--r--drivers/xen/xenbus/xenbus_probe.c31
1 files changed, 31 insertions, 0 deletions
diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
index c8f0282bb649..18ffd0551b54 100644
--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -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);