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[Qemu-devel] [PULL 05/10] watchdog: fix deadlock with -watchdog-action p
From: |
Paolo Bonzini |
Subject: |
[Qemu-devel] [PULL 05/10] watchdog: fix deadlock with -watchdog-action pause |
Date: |
Thu, 10 Jul 2014 18:04:08 +0200 |
qemu_clock_enable says:
/* Disabling the clock will wait for related timerlists to stop
* executing qemu_run_timers. Thus, this functions should not
* be used from the callback of a timer that is based on @clock.
* Doing so would cause a deadlock.
*/
and it indeed does: vm_stop uses qemu_clock_enable on QEMU_CLOCK_VIRTUAL
and watchdogs are based on QEMU_CLOCK_VIRTUAL, and we get a deadlock.
Use qemu_system_vmstop_request_prepare()/qemu_system_vmstop_request()
instead; yet another alternative could be a BH.
I checked other occurrences of vm_stop and they should not have this
problem. RUN_STATE_IO_ERROR could in principle (it depends on the
code in the drivers) but it has been fixed by commit 2bd3bce, "block:
asynchronously stop the VM on I/O errors", 2014-06-05.
Tested-by: Luiz Capitulino <address@hidden>
Signed-off-by: Paolo Bonzini <address@hidden>
---
hw/watchdog/watchdog.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/hw/watchdog/watchdog.c b/hw/watchdog/watchdog.c
index 9f607d4..c307f9b 100644
--- a/hw/watchdog/watchdog.c
+++ b/hw/watchdog/watchdog.c
@@ -122,8 +122,12 @@ void watchdog_perform_action(void)
exit(0);
case WDT_PAUSE: /* same as 'stop' command in monitor */
+ /* In a timer callback, when vm_stop calls qemu_clock_enable
+ * you would get a deadlock. Bypass the problem.
+ */
+ qemu_system_vmstop_request_prepare();
qapi_event_send_watchdog(WATCHDOG_EXPIRATION_ACTION_PAUSE,
&error_abort);
- vm_stop(RUN_STATE_WATCHDOG);
+ qemu_system_vmstop_request(RUN_STATE_WATCHDOG);
break;
case WDT_DEBUG:
--
1.8.3.1
- [Qemu-devel] [PULL v3 00/10] KVM changes (+ misc small fixes) for 2.1, Paolo Bonzini, 2014/07/10
- [Qemu-devel] [PULL 02/10] mips/kvm: Disable FPU on reset with KVM, Paolo Bonzini, 2014/07/10
- [Qemu-devel] [PULL 01/10] mips/kvm: Init EBase to correct KSEG0, Paolo Bonzini, 2014/07/10
- [Qemu-devel] [PULL 03/10] mips_malta: Remove incorrect KVM T&E references, Paolo Bonzini, 2014/07/10
- [Qemu-devel] [PULL 04/10] mips_malta: Catch kernels linked at wrong address, Paolo Bonzini, 2014/07/10
- [Qemu-devel] [PULL 06/10] Enforce stack protector usage, Paolo Bonzini, 2014/07/10
- [Qemu-devel] [PULL 08/10] oslib-posix: Fix new compiler error with -Wclobbered, Paolo Bonzini, 2014/07/10
- [Qemu-devel] [PULL 05/10] watchdog: fix deadlock with -watchdog-action pause,
Paolo Bonzini <=
- [Qemu-devel] [PULL 09/10] mc146818rtc: register the clock reset notifier on the right clock, Paolo Bonzini, 2014/07/10
- [Qemu-devel] [PULL 07/10] target-i386: Add "kvmclock-stable-bit" feature bit name, Paolo Bonzini, 2014/07/10
- [Qemu-devel] [PULL 10/10] qtest: fix vhost-user-test compilation with old GLib, Paolo Bonzini, 2014/07/10
- Re: [Qemu-devel] [PULL v3 00/10] KVM changes (+ misc small fixes) for 2.1, Peter Maydell, 2014/07/11