[Xen-devel] [PATCH 2/7] xen: sched_rt: implement the .free_pdata hook

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

which is called by cpu_schedule_down(), and is necessary
for resetting the spinlock pointers in schedule_data from
the RTDS global runqueue lock, back to the default _lock
fields in the struct.

Not doing so causes Xen to explode, e.g., when removing
pCPUs from an RTDS cpupool and assigning them to another
one.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Cc: Meng Xu <xumengpanda@xxxxxxxxx>
Cc: Jan Beulich <JBeulich@xxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
---
 xen/common/sched_rt.c |   18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/xen/common/sched_rt.c b/xen/common/sched_rt.c
index 055a50f..3e37e62 100644
--- a/xen/common/sched_rt.c
+++ b/xen/common/sched_rt.c
@@ -444,6 +444,23 @@ rt_alloc_pdata(const struct scheduler *ops, int cpu)
     return (void *)1;
 }
 
+static void
+rt_free_pdata(const struct scheduler *ops, void *pcpu, int cpu)
+{
+    struct rt_private *prv = rt_priv(ops);
+    struct schedule_data *sd = &per_cpu(schedule_data, cpu);
+    unsigned long flags;
+
+    spin_lock_irqsave(&prv->lock, flags);
+
+    /* Move spinlock back to the default lock */
+    ASSERT(sd->schedule_lock == &prv->lock);
+    ASSERT(!spin_is_locked(&sd->_lock));
+    sd->schedule_lock = &sd->_lock;
+
+    spin_unlock_irqrestore(&prv->lock, flags);
+}
+
 static void *
 rt_alloc_domdata(const struct scheduler *ops, struct domain *dom)
 {
@@ -1090,6 +1107,7 @@ const struct scheduler sched_rtds_def = {
     .init           = rt_init,
     .deinit         = rt_deinit,
     .alloc_pdata    = rt_alloc_pdata,
+    .free_pdata     = rt_free_pdata,
     .alloc_domdata  = rt_alloc_domdata,
     .free_domdata   = rt_free_domdata,
     .init_domain    = rt_dom_init,


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