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authorRusty Russell <rusty@rustcorp.com.au>2009-06-12 22:27:02 -0600
committerRusty Russell <rusty@rustcorp.com.au>2009-06-12 22:27:02 +0930
commitabd41f037e1a64543000ed73b42f616d04d92700 (patch)
treed9013e66f4d8fc66fc92ce0587f8d126e156b253 /drivers/lguest/core.c
parentebf9a5a99c1a464afe0b4dfa64416fc8b273bc5c (diff)
lguest: fix race in halt code
When the Guest does the LHCALL_HALT hypercall, we go to sleep, expecting that a timer or the Waker will wake_up_process() us. But we do it in a stupid way, leaving a classic missing wakeup race. So split maybe_do_interrupt() into interrupt_pending() and try_deliver_interrupt(), and check maybe_do_interrupt() and the "break_out" flag before calling schedule. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Diffstat (limited to 'drivers/lguest/core.c')
-rw-r--r--drivers/lguest/core.c14
1 files changed, 12 insertions, 2 deletions
diff --git a/drivers/lguest/core.c b/drivers/lguest/core.c
index 4845fb3cf74b..8ca1def5b142 100644
--- a/drivers/lguest/core.c
+++ b/drivers/lguest/core.c
@@ -188,6 +188,8 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
{
/* We stop running once the Guest is dead. */
while (!cpu->lg->dead) {
+ unsigned int irq;
+
/* First we run any hypercalls the Guest wants done. */
if (cpu->hcall)
do_hypercalls(cpu);
@@ -211,7 +213,9 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
/* Check if there are any interrupts which can be delivered now:
* if so, this sets up the hander to be executed when we next
* run the Guest. */
- maybe_do_interrupt(cpu);
+ irq = interrupt_pending(cpu);
+ if (irq < LGUEST_IRQS)
+ try_deliver_interrupt(cpu, irq);
/* All long-lived kernel loops need to check with this horrible
* thing called the freezer. If the Host is trying to suspend,
@@ -227,7 +231,13 @@ int run_guest(struct lg_cpu *cpu, unsigned long __user *user)
* clock timer or LHREQ_BREAK from the Waker will wake us. */
if (cpu->halted) {
set_current_state(TASK_INTERRUPTIBLE);
- schedule();
+ /* Just before we sleep, make sure nothing snuck in
+ * which we should be doing. */
+ if (interrupt_pending(cpu) < LGUEST_IRQS
+ || cpu->break_out)
+ set_current_state(TASK_RUNNING);
+ else
+ schedule();
continue;
}