On 12/1/11 4:42 PM, Andriy Gapon wrote:
on 01/12/2011 22:53 John Baldwin said the following:
On Thursday, December 01, 2011 3:42:24 pm Andriy Gapon wrote:
Returning to critical_exit, what do you think about the following patch?
I guess that it could be committed independently of / before the
SCHEDULER_STOPPED thing.
commit ee3d1a04985e86911a68d854439ae8c5429b7bd5
Author: Andriy Gapon<a...@icyb.net.ua>
Date: Thu Dec 1 18:53:36 2011 +0200
critical_exit: ignore td_owepreempt if kdb_active
calling mi_switch in such a context result in a recursion via
kdb_switch
diff --git a/sys/kern/kern_switch.c b/sys/kern/kern_switch.c
index 93cbf7b..885dc22 100644
--- a/sys/kern/kern_switch.c
+++ b/sys/kern/kern_switch.c
@@ -200,7 +200,7 @@ critical_exit(void)
if (td->td_critnest == 1) {
td->td_critnest = 0;
- if (td->td_owepreempt) {
+ if (td->td_owepreempt&& !kdb_active) {
td->td_critnest = 1;
thread_lock(td);
td->td_critnest--;
I think this is fine, but I'd probably change this to SCHEDULER_STOPPED()
in the SCHEDULER_STOPPED() patch.
I don't understand why... What if kdb is entered for some other reason, not
because of panic? In that case SCHEDULER_STOPPED() would be false, but it is
still possible to find a way into mi_switch.
The SCHEDULER_STOPPED patch adds this:
@@ -428,6 +428,8 @@ mi_switch(int flags, struct thread *newtd)
*/
if (kdb_active)
kdb_switch();
+ if (SCHEDULER_STOPPED())
+ return;
if (flags& SW_VOL) {
td->td_ru.ru_nvcsw++;
td->td_swvoltick = ticks;
Ah, ok (I had thought SCHEDULER_STOPPED was going to always be true when
kdb was active). But I think these two changes should cover
critical_exit() ok.
--
John Baldwin
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