[Xen-devel] [PATCH] xen: credit2: fix spinlock irq-safety violation

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

In commit ad4b3e1e9df34 ("xen: credit2: implement
utilization cap") xfree() was being called (for
deallocating the budget replenishment timer, during
domain destruction) inside an IRQ disabled critical
section.

That must not happen, as it uses the mem-pool's lock,
which needs to be taken with IRQ enabled. And, in fact,
we crash (in debug builds):

(XEN) ****************************************
(XEN) Panic on CPU 0:
(XEN) Xen BUG at spinlock.c:47
(XEN) ****************************************

Let's, therefore, kill and deallocate the timer outside of
the critical sections, when IRQs are enabled.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
---
Cc: osstest service owner <osstest-admin@xxxxxxxxxxxxxx>
Cc: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
This was spotted by OSSTest's flight 113562:

 http://logs.test-lab.xenproject.org/osstest/logs/113562/
 
http://logs.test-lab.xenproject.org/osstest/logs/113562/test-amd64-amd64-xl-credit2/serial-godello0.log
---
 xen/common/sched_credit2.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
index 32234ac..7a550db 100644
--- a/xen/common/sched_credit2.c
+++ b/xen/common/sched_credit2.c
@@ -2923,13 +2923,13 @@ csched2_free_domdata(const struct scheduler *ops, void 
*data)
 
     write_lock_irqsave(&prv->lock, flags);
 
-    kill_timer(sdom->repl_timer);
-    xfree(sdom->repl_timer);
-
     list_del_init(&sdom->sdom_elem);
 
     write_unlock_irqrestore(&prv->lock, flags);
 
+    kill_timer(sdom->repl_timer);
+    xfree(sdom->repl_timer);
+
     xfree(data);
 }
 


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel