From 30e5210a706ca6b52cbefa8b71e40ae614ffd6e5 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 27 Jun 2014 16:31:07 +0200 Subject: watchdog: fix deadlock with -watchdog-action pause 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 Signed-off-by: Paolo Bonzini --- hw/watchdog/watchdog.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) (limited to 'hw') 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: -- cgit v1.1