| Message ID | 20170405132503.32125-13-alex.bennee@linaro.org |
|---|---|
| State | Superseded |
| Headers | show |
| Series | icount and misc MTTCG fixes for 2.9-rc4 | expand |
> From: Alex Bennée [mailto:alex.bennee@linaro.org] > > If we find ourselves trying to add an event to the log where time has > gone backwards it is because a vCPU event has occurred and the > main-loop is not yet aware of time moving forward. This should not > happen and if it does its better to fail early than generate a log > that will have weird behaviour. > > Signed-off-by: Alex Bennée <alex.bennee@linaro.org> > --- > replay/replay-internal.c | 4 ++++ > replay/replay.c | 4 ++++ > 2 files changed, 8 insertions(+) > > diff --git a/replay/replay-internal.c b/replay/replay-internal.c > index bea7b4aa6b..fca8514012 100644 > --- a/replay/replay-internal.c > +++ b/replay/replay-internal.c > @@ -195,6 +195,10 @@ void replay_save_instructions(void) > if (replay_file && replay_mode == REPLAY_MODE_RECORD) { > replay_mutex_lock(); > int diff = (int)(replay_get_current_step() - replay_state.current_step); > + > + /* Time can only go forward */ > + assert(diff >= 0); > + > if (diff > 0) { This "if" is useless then. > replay_put_event(EVENT_INSTRUCTION); > replay_put_dword(diff); > diff --git a/replay/replay.c b/replay/replay.c > index 9e0724e756..f810628cac 100644 > --- a/replay/replay.c > +++ b/replay/replay.c > @@ -84,6 +84,10 @@ void replay_account_executed_instructions(void) > if (replay_state.instructions_count > 0) { > int count = (int)(replay_get_current_step() > - replay_state.current_step); > + > + /* Time can only go forward */ > + assert(count >= 0); > + > replay_state.instructions_count -= count; > replay_state.current_step += count; > if (replay_state.instructions_count == 0) { > -- > 2.11.0 Pavel Dovgalyuk
On 05/04/2017 15:33, Pavel Dovgalyuk wrote: >> + >> + /* Time can only go forward */ >> + assert(diff >= 0); >> + >> if (diff > 0) { > This "if" is useless then. > It isn't, "diff == 0" can happen. Paolo
Paolo Bonzini <pbonzini@redhat.com> writes: > On 05/04/2017 15:33, Pavel Dovgalyuk wrote: >>> + >>> + /* Time can only go forward */ >>> + assert(diff >= 0); >>> + >>> if (diff > 0) { >> This "if" is useless then. >> > > It isn't, "diff == 0" can happen. In my previous patchset I actually output-ed a EVENT_INSTRUCTION with a zero diff for the negative case although it does seem redundant to output that if we can avoid it? -- Alex Bennée
diff --git a/replay/replay-internal.c b/replay/replay-internal.c index bea7b4aa6b..fca8514012 100644 --- a/replay/replay-internal.c +++ b/replay/replay-internal.c @@ -195,6 +195,10 @@ void replay_save_instructions(void) if (replay_file && replay_mode == REPLAY_MODE_RECORD) { replay_mutex_lock(); int diff = (int)(replay_get_current_step() - replay_state.current_step); + + /* Time can only go forward */ + assert(diff >= 0); + if (diff > 0) { replay_put_event(EVENT_INSTRUCTION); replay_put_dword(diff); diff --git a/replay/replay.c b/replay/replay.c index 9e0724e756..f810628cac 100644 --- a/replay/replay.c +++ b/replay/replay.c @@ -84,6 +84,10 @@ void replay_account_executed_instructions(void) if (replay_state.instructions_count > 0) { int count = (int)(replay_get_current_step() - replay_state.current_step); + + /* Time can only go forward */ + assert(count >= 0); + replay_state.instructions_count -= count; replay_state.current_step += count; if (replay_state.instructions_count == 0) {
If we find ourselves trying to add an event to the log where time has gone backwards it is because a vCPU event has occurred and the main-loop is not yet aware of time moving forward. This should not happen and if it does its better to fail early than generate a log that will have weird behaviour. Signed-off-by: Alex Bennée <alex.bennee@linaro.org> --- replay/replay-internal.c | 4 ++++ replay/replay.c | 4 ++++ 2 files changed, 8 insertions(+) -- 2.11.0