Our current interrupt handlers assume that they leave over the same task
and CPU they entered. But CONFIG_XENO_HW_UNLOCKED_SWITCH and commit
f6af9b831c broke this assumption: xnpod_schedule invoked from the
handler tail can now actually trigger a domain migration, and that can
also include a CPU migration. This causes subtle corruptions as invalid
xnstat_exectime_t objects may be restored and - even worse - we may
improperly flush XNHTICK of the old CPU, leaving Linux timer-wise dead
there (as happened to us).
Fix this by moving XNHTICK replay and exectime accounting before the
scheduling point. Note that this introduces a tiny imprecision in the
accounting.
Signed-off-by: Jan Kiszka <jan.kis...@siemens.com>
---
This is also 2.5 material.
ksrc/nucleus/intr.c | 22 ++++++++++++++--------
1 files changed, 14 insertions(+), 8 deletions(-)
diff --git a/ksrc/nucleus/intr.c b/ksrc/nucleus/intr.c
index 3769949..fd3679a 100644
--- a/ksrc/nucleus/intr.c
+++ b/ksrc/nucleus/intr.c
@@ -116,10 +116,6 @@ void xnintr_clock_handler(void)
xnstat_exectime_lazy_switch(sched,
&nkclock.stat[xnsched_cpu(sched)].account, start);
- if (--sched->inesting == 0) {
- __clrbits(sched->lflags, XNINIRQ);
- xnpod_schedule();
- }
/*
* If the clock interrupt preempted a real-time thread, any
* transition to the root thread has already triggered a host
@@ -131,8 +127,14 @@ void xnintr_clock_handler(void)
xnthread_test_state(sched->curr, XNROOT))
xnintr_host_tick(sched);
- trace_mark(xn_nucleus, irq_exit, "irq %u", XNARCH_TIMER_IRQ);
xnstat_exectime_switch(sched, prev);
+
+ if (--sched->inesting == 0) {
+ __clrbits(sched->lflags, XNINIRQ);
+ xnpod_schedule();
+ }
+
+ trace_mark(xn_nucleus, irq_exit, "irq %u", XNARCH_TIMER_IRQ);
}
/* Optional support for shared interrupts. */
@@ -219,13 +221,14 @@ static void xnintr_shirq_handler(unsigned irq, void
*cookie)
else if (!(s & XN_ISR_NOENABLE))
xnarch_end_irq(irq);
+ xnstat_exectime_switch(sched, prev);
+
if (--sched->inesting == 0) {
__clrbits(sched->lflags, XNINIRQ);
xnpod_schedule();
}
trace_mark(xn_nucleus, irq_exit, "irq %u", irq);
- xnstat_exectime_switch(sched, prev);
}
/*
@@ -302,12 +305,14 @@ static void xnintr_edge_shirq_handler(unsigned irq, void
*cookie)
else if (!(s & XN_ISR_NOENABLE))
xnarch_end_irq(irq);
+ xnstat_exectime_switch(sched, prev);
+
if (--sched->inesting == 0) {
__clrbits(sched->lflags, XNINIRQ);
xnpod_schedule();
}
+
trace_mark(xn_nucleus, irq_exit, "irq %u", irq);
- xnstat_exectime_switch(sched, prev);
}
static inline int xnintr_irq_attach(xnintr_t *intr)
@@ -492,13 +497,14 @@ static void xnintr_irq_handler(unsigned irq, void *cookie)
else if (!(s & XN_ISR_NOENABLE))
xnarch_end_irq(irq);
+ xnstat_exectime_switch(sched, prev);
+
if (--sched->inesting == 0) {
__clrbits(sched->lflags, XNINIRQ);
xnpod_schedule();
}
trace_mark(xn_nucleus, irq_exit, "irq %u", irq);
- xnstat_exectime_switch(sched, prev);
}
int __init xnintr_mount(void)
--
1.7.1
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