From 0c08185f8fe1eb20edec1a2bf32b4d219cc023f0 Mon Sep 17 00:00:00 2001 From: Pavel Dovgalyuk Date: Wed, 12 Sep 2018 11:19:45 +0300 Subject: [PATCH] replay: wake up vCPU when replaying In record/replay icount mode vCPU thread and iothread synchronize the execution using the checkpoints. vCPU thread processes the virtual timers and iothread processes all others. When iothread wants to wake up sleeping vCPU thread, it sends dummy queued work. Therefore it could be the following sequence of the events in record mode: - IO: sending dummy work - IO: processing timers - CPU: wakeup - CPU: clearing dummy work - CPU: processing virtual timers But due to the races in replay mode the sequence may change: - IO: sending dummy work - CPU: wakeup - CPU: clearing dummy work - CPU: sleeping again because nothing to do - IO: Processing timers - CPU: zzzz In this case vCPU will not wake up, because dummy work is not to be set up again. This patch tries to wake up the vCPU when it sleeps and the icount warp checkpoint isn't met. It means that vCPU has something to do, because there are no other reasons of non-matching warp checkpoint. Signed-off-by: Pavel Dovgalyuk -- v5: improve checking that vCPU is still sleeping Message-Id: <20180912081945.3228.19776.stgit@pasha-VirtualBox> Signed-off-by: Paolo Bonzini --- cpus.c | 31 +++++++++++++++++++++---------- include/sysemu/replay.h | 3 +++ replay/replay.c | 12 ++++++++++++ 3 files changed, 36 insertions(+), 10 deletions(-) diff --git a/cpus.c b/cpus.c index d8b3b46cc80..68f08f5b2d8 100644 --- a/cpus.c +++ b/cpus.c @@ -583,18 +583,29 @@ void qemu_start_warp_timer(void) return; } - /* warp clock deterministically in record/replay mode */ - if (!replay_checkpoint(CHECKPOINT_CLOCK_WARP_START)) { - return; - } + if (replay_mode != REPLAY_MODE_PLAY) { + if (!all_cpu_threads_idle()) { + return; + } - if (!all_cpu_threads_idle()) { - return; - } + if (qtest_enabled()) { + /* When testing, qtest commands advance icount. */ + return; + } - if (qtest_enabled()) { - /* When testing, qtest commands advance icount. */ - return; + replay_checkpoint(CHECKPOINT_CLOCK_WARP_START); + } else { + /* warp clock deterministically in record/replay mode */ + if (!replay_checkpoint(CHECKPOINT_CLOCK_WARP_START)) { + /* vCPU is sleeping and warp can't be started. + It is probably a race condition: notification sent + to vCPU was processed in advance and vCPU went to sleep. + Therefore we have to wake it up for doing someting. */ + if (replay_has_checkpoint()) { + qemu_clock_notify(QEMU_CLOCK_VIRTUAL); + } + return; + } } /* We want to use the earliest deadline from ALL vm_clocks */ diff --git a/include/sysemu/replay.h b/include/sysemu/replay.h index 3ced6bc2312..7f7a594eca9 100644 --- a/include/sysemu/replay.h +++ b/include/sysemu/replay.h @@ -120,6 +120,9 @@ void replay_shutdown_request(ShutdownCause cause); Returns 0 in PLAY mode if checkpoint was not found. Returns 1 in all other cases. */ bool replay_checkpoint(ReplayCheckpoint checkpoint); +/*! Used to determine that checkpoint is pending. + Does not proceed to the next event in the log. */ +bool replay_has_checkpoint(void); /* Asynchronous events queue */ diff --git a/replay/replay.c b/replay/replay.c index 82282614011..379b51ab46f 100644 --- a/replay/replay.c +++ b/replay/replay.c @@ -224,6 +224,18 @@ out: return res; } +bool replay_has_checkpoint(void) +{ + bool res = false; + if (replay_mode == REPLAY_MODE_PLAY) { + g_assert(replay_mutex_locked()); + replay_account_executed_instructions(); + res = EVENT_CHECKPOINT <= replay_state.data_kind + && replay_state.data_kind <= EVENT_CHECKPOINT_LAST; + } + return res; +} + static void replay_enable(const char *fname, int mode) { const char *fmode = NULL; -- 2.39.2