systemc: Add a distinct async_request_update mechanism.

This mechanism had just been plumbed into the regular request_update,
but that doesn't have any thread safety which is the whole point of
async_request_update. This new mechanism puts async update requests
into their own list which is checked any time normal updates happen.

The delta cycle which triggers those updates must happen through some
other means which will usually be ok. The exact timing of the update
is undefined, so it would be legal for it to either not be recognized
before the impending end of the simulation, or for it to get picked up
by subsequent activity. If there isn't subsequent activity but the
simulation also doesn't end, for instance if there are only gem5 events
left, then that update could be lost. That is an unresolved issue.

It would be nice to schedule a "ready" event if async updates were
added which would ensure they wouldn't starve. Unfortunately that
requires the event queue lock, and in practice it's been found that a
systemc process might block, effectively holding the event queue lock,
while it waits for some asyncrhonous update to give it something to do.
This effectively deadlocks the system since the update is blocked on
the lock the main thread holds, and the main thread is blocked waiting
for the update.

Change-Id: I580303db01673faafc2e63545b6a69b3327a521c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/18288
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>

systemc: Make sc_(pause|stop) exit to python when not using sc_main.

In those cases, there's no sc_main to return control to. The python
config script is serving more or less the same purpose, so we can
return control to there instead.

Change-Id: I3cf0623ae51d989b883fb8556ebbf44651bbec99
Reviewed-on: https://gem5-review.googlesource.com/c/16445
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Init some values in the scheduler for running without sc_main.

When running without sc_main, sc_start won't be called, and therefore
runToTime and maxTick won't be initialized. To avoid the scheduler
getting confused and behaving erratically, those values should be
initialized to something that makes sense in situations where there's
no sc_main.

Change-Id: I6ddd7db9ecb36d716eb5ef75e1c38bb99a386092
Reviewed-on: https://gem5-review.googlesource.com/c/16443
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Handle exceptions "correctly" even if sc_main hasn't been run.

If sc_main hasn't run, for instance if there isn't an sc_main and gem5
is orchestrating the simulation directly, then exceptions shouldn't be
thrown to the sc_main fiber since it isn't running and may not be able
to run since sc_main may not even exist.

Instead, we need to check whether it makes sense to throw to sc_main,
and if not pass the exception directly to the report handler since
there likely won't be anyone to catch it if we just throw it from the
scheduler or into general purpose gem5.

Since the name throwToScMain is no longer a complete description for
what that function does, this change renames it to throwUp, since it
will now throw exceptions up the stack, either to sc_main or to the
conceptual top level by going directly to the report handler.

Change-Id: Ibdc92c9cf213ec6aa15ad654862057b7bf2e1c8e
Reviewed-on: https://gem5-review.googlesource.com/c/16442
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Update signals before initing processes.

We were supposed to do one update phase before adding all processes
which didn't have dont_initialize() called to the run queue. We were
doing that in the opposite order.

Change-Id: I6dd4108040d455dc78029da029a2eb5e7af819cb
Reviewed-on: https://gem5-review.googlesource.com/c/14915
Reviewed-by: Matthias Jung <jungma@eit.uni-kl.de>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Seperate out the sc_main fiber and its bookkeeping.

By pulling out the sc_main fiber (scMainFiber), we can make it
available to different entities in the simulator and avoid having to
have parallel bookkeeping.

Also this will make it possible to hook into sc_main without putting
the code in sc_main.cc.

Change-Id: I7689441424238e9b2e4d2b48e945dea35fd8cc5d
Reviewed-on: https://gem5-review.googlesource.com/c/13977
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Add an accessor for getting the current process.

This is to avoid having to expose the scheduler (which tracks the
current process) to header files which should be independent of gem5
and the underlying implementation.

Change-Id: I1b0810ab66c3ce52b5b94236d7df86da66a62472
Reviewed-on: https://gem5-review.googlesource.com/c/13335
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Don't re-schedule a process which is already scheduled.

Change-Id: I8e12713c49aad03d0bfb779883adcbfa8fd4b42e
Reviewed-on: https://gem5-review.googlesource.com/c/13334
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Switch to using predefined messages for core.

Create and use predefined messages for core which match the ones
Accellera uses.

Change-Id: I05b1398933f753946d5917f39d0f39c7cb45ed9f
Reviewed-on: https://gem5-review.googlesource.com/c/13323
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Refactor reporting to prep for int based messages.

There's a deprecated reporting mechanism based on integer message ids,
and the reporting mechanism needs to be refactored a bit to make it
easier to support.

Some bookkeeping data structures were moved out to somewhere they
can be accessed by other code, obviating the non-standard get_handler
function.

Change-Id: Id427cd79be9ef0f3275fbac39ff047ab672fb3e0
Reviewed-on: https://gem5-review.googlesource.com/c/13318
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: If a process hasn't started, still signal its reset event.

Change-Id: I9c8026cde455070841139d02955f5c083b9e0645
Reviewed-on: https://gem5-review.googlesource.com/c/13314
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Run delta notifications in reverse insertion order.

This is sort of pointless, except that it matches Accellera's behavior.

Change-Id: Ia63f2de998157aa68ce36fdc2ba39ca7a80fecbe
Reviewed-on: https://gem5-review.googlesource.com/c/13295
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Clear the current process when done with the eval phase.

The current process will still be set sometimes when exiting from the
yield loop in the top of runReady in the scheduler. Clear it to ensure
that we don't think a process is running when it isn't.

Change-Id: Idd44689e10fadf4a3e3ec07c60d107c80a44d39f
Reviewed-on: https://gem5-review.googlesource.com/c/13201
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Modify reportifyException to keep sc_reports in scope.

reportifyException was sometimes indirectly creating temporary
sc_report objects which would go out of scope when they were
returned. The later code which tried to print them would then read
garbage.

Change-Id: I0a744eb029c62bf2ffee83db0a0e6dcbe3e60f7d
Reviewed-on: https://gem5-review.googlesource.com/c/13190
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement signal based resets.

The implementation is based on sc_event sensitivities.

Also of note is that the way reset works in the Accellera
implementation isn't consistent with the spec. That says that
wait(int n) is supposed to be equivalent to calling wait() n times,
assuming n is greater than 0.

Instead, Accellera stores that count and then doesn't wake up the
process until the count is 0, decrementing it otherwise.

That means that when the process is in reset, it won't actually reset
for those intermediate wait()s which it would if wait() was called
repeatedly. Also, oddly, when a reset becomes asserted, it will clear
the count to 0 explicitly. That may have been an attempt to make the
behavior of wait(int n) match the spec, but it doesn't handle cases
where the reset is already set when wait(int n) is called.

Change-Id: I92f8e9a128e6618af94dc048ce570a4436e17e4b
Reviewed-on: https://gem5-review.googlesource.com/c/13186
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement the synchronous reset state.

Change-Id: Ie0c29bb6cf918aea1c0bc719b9d37628b5b19339
Reviewed-on: https://gem5-review.googlesource.com/c/13185
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement general and VCD trace support.

This doesn't include WIF trace support, but does make allowances for
adding it in the future.

Change-Id: Ifb62f40a7d8a13e94463930a44ac4b1cf41e3009
Reviewed-on: https://gem5-review.googlesource.com/c/12826
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Don't schedule the ready event unnecessarily.

If we're already going to process the thing we'd be scheduling it to
process, just let the existing invocation get to it.

Change-Id: Ifeebc80903065567fc0eed02beefec6156b22ff7
Reviewed-on: https://gem5-review.googlesource.com/c/12964
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Change how the scheduler orders processes.

The Accellera implementation looks like it does all the methods, then
all the threads, and then loops back and tries again, and there are
even comments in the code that suggests that. What it actually does,
however, is runs all the methods, then runs a single thread if one is
waiting, and then starts over. The effect is that the scheduler will
run any methods first, then run threads until a method might have
become ready, and then repeat.

This will actually result in more mixing of threads and methods, more
context switches, and worse performance, but it makes the regressions
pass more.

Change-Id: I7cb0485e26eed79204ff2a3c3ded27b973e0b7b0
Reviewed-on: https://gem5-review.googlesource.com/c/12808
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Rework how delayed sensitivities are handled.

Make BindInfo into a more general purpose Port class which mirrors
sc_module and Module, sc_object and Object, etc. This tracks multiple
bindings internally, and also pending sensitivities. Keep a global
list of ports which are added in reverse order to match Accellera, and
which is iterated over to finalize binding and for phase callbacks.
This is as opposed to doing it one module at a time, and is to better
match Accellera's ordering for the regressions.

Also the sensitivity classes are now built with factory functions,
which gets around problems calling virtual functions from their
constructors or forgetting to having to have extra boilerplate each
place they're constructed.

The port class also now finalizes port or event finder sensitivities
when its binding is completed, unless it's already complete in which
case it does so immediately.

Change-Id: I1b01689715c425b94e0f68cf0271f5c1565d8c61
Reviewed-on: https://gem5-review.googlesource.com/c/12806
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Add some error checks to some classes.

These check whether those classes are being constructed in legal
circumstances, and avoids a null pointer dereference.

Change-Id: Ied36ee15c3d7bf6ee444351a841c38576780298e
Reviewed-on: https://gem5-review.googlesource.com/c/12622
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Keep all pre-init processes on a single list.

We were keeping track of processes which should be initialized and
those which shouldn't on two different lists, and then processing
each list one after the other. This could reorder processes from the
order they were created, and so cause spurious differences which cause
the Accellera tests to fail.

This does make the scheduler slightly simpler, so it's not all bad.

Change-Id: I63306a41ce7bea91fa9ff2f6774ce9150134ce48
Reviewed-on: https://gem5-review.googlesource.com/c/12613
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Catch exceptions during updates, notifications, and callbacks.

Change-Id: I6005c12ce32d24413618e3955625432985f99f69
Reviewed-on: https://gem5-review.googlesource.com/c/12607
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Track the scheduler status using an enum instead of bools.

The scheduler tracked whether it was paused or stopped with two bools
which are mutually exclusive. It's useful to be able to also check for
some other mutually exclusive states like what phase the scheduler is
currently running.

Rather than adding a bunch of additional bools, this change switches
those mutually exclusive states over to an enum, and adds some methods
to access and maintain that enum.

Change-Id: Ia9696b2853d1b122c1100c9df0e12b018fe9b84b
Reviewed-on: https://gem5-review.googlesource.com/c/12605
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Fortify how exceptions are caught and passed around.

This change tightens up exception catching and makes gem5's systemc
code react to exceptions more in line with the Accellera
implementation. This prevents exceptions from being caught by the
pybind11 integration which makes it very difficult to see where an
exception came from, and makes the output differ by including a
(mostly useless) backtrace.

Change-Id: I7130d53a98fadd137073d1718f780f32f57c658c
Reviewed-on: https://gem5-review.googlesource.com/c/12601
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Warn if a process is dont_initialize with no static sensitivieis.

Change-Id: I4db64f42872a6fb459faa401abdad3f168297347
Reviewed-on: https://gem5-review.googlesource.com/c/12599
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Match how Accellera schedules processes even more closely.

The Accellera implementation runs processes in a cycle where it first
runs all the methods it has, then all the threads, and then starts
again in case any new methods have been scheduled. This keeps methods
and processes in the order they were marked ready (what a prior change
made this scheduler do), but also keeps the methods together and the
threads together (something it used to do, but that change made it
stop doing). This change should make the gem5 scheduler match in both
respects.

Note that its correct to run the processes in whatever order we want,
it's just that if we're going to compare against the "golden" output
from the Accellera tests, we need to match the order to get sensible
results.

Change-Id: I0b1e4ed24c56f97921148b74e90c2dca5fd3fbc4
Reviewed-on: https://gem5-review.googlesource.com/c/12595
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: When stopping immediately, block new processes/updates.

When stopping immediately, we're supposed to finish the current
process but not run any other processes or go to the update phase. The
rest of the process could introduce new processes or request new
updates, so we need to make sure we block those if we're in the process
of stopping.

Change-Id: I9cc867d294cf171dfedb4b9d43fbc167c2057de8
Reviewed-on: https://gem5-review.googlesource.com/c/12466
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Toggle off clumping methods together in the ready list.

This is totally legal and good for performance, but because some of
Accellera's tests depend on processes which can run in any order
running in a particular order to reproduce the golden output, it needs
to be disabled to pass the tests.

This change leaves it as an option which could even be plumbed out in
the future to support some sort of "compatibility" mode with the tests.

An alternative would be to verify that the tests pass, change the
ordering to the alternative (but still correct) order, and then
update the reference output.

Change-Id: I113a40dec52f8b623253f8a27886b4a0abe89485
Reviewed-on: https://gem5-review.googlesource.com/c/12457
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Store timed notifications in a list instead of a set.

This has three advantages. First, the data structure doesn't have to
try to keep track of whether or not an event is already listed there.
Second, it's easier to delete an item by storing an iterator for it
when it gets inserted. Third, the ordering of events is not dependent
on the arbitrary ordering of the set, it's bsaed on the fixed order
the events get added to the list.

One part of this change makes ScEvent-s keep track of what list they're
on, and handle their own insertion and deletion when they're
scheduled or descheduled. A side effect of that is that it's no longer
safe to simply use a range based for loop to loop over all of an
ScEvent and deschedule all its events or to run then (which deschedules
them internally once they execute).

That can be avoided by looping until the list is empty, and operating
on the first element. As the first element is processed and removed
from the list, the next element will become first and will get picked
up in the next iteration.

Change-Id: Icad51a63f153297c88e65f85d22ac721e6c571d8
Reviewed-on: https://gem5-review.googlesource.com/c/12456
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Add a "changeStamp" value to the scheduler.

This value is incremented after each delta cycle's evaluate stage and
after timed notifications happen. Its value is used by some channels
to determine whether certain events happened within the previous update
phase to implement the "event()", "posedge()", and "negedge()"
functions.

Change-Id: I9a73f0b5007dcbb6a74da9d666f28da1930b9d3d
Reviewed-on: https://gem5-review.googlesource.com/c/12452
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Keep track of more cases when we should be ready after resume.

If a thread self suspends, it should be marked as ready after resuming.
If a process was already ready when suspended, it should also be
remarked as ready after resuming.

Special care has to be taken in pre-initialization situations so that
processes are put on the right lists, and whether a process is tracked
is already marked as ready.

Change-Id: I15da7d747db591785358d47781297468c5f9fd09
Reviewed-on: https://gem5-review.googlesource.com/c/12445
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Fix some issues with starvation checks.

Make sure we check for starvation after timed notifications and at the
very end of delta cycles (after delta notifications, not before). Also
reverse the order of starvation checks (whether they apply at all, then
if they're satisfied) to make those checks faster. Checking a bool
is a lot easier than checking if a bunch of other structures are
empty.

Change-Id: I514ff219909823f1f424fde69856d6b510655188
Reviewed-on: https://gem5-review.googlesource.com/12268
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: When sc_start-ing with zero time, ensure the ready event runs.

The ready event is what notices that we only wanted to run one delta
cycle, or no delta cycle if there was nothing to do, and return to
sc_main. If the ready event wasn't scheduled, we would advance time
before the ready event ran and returned to sc_main which is incorrect.

Change-Id: Ic3c10a2f1405f744e8c2bd37aa45846ee6e98e12
Reviewed-on: https://gem5-review.googlesource.com/12267
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Make sure methods aren't restarted by yield.

Methods may need to yield control to other Processes when throwing
them exceptions. In that case, we need to keep track of the fact that
the method doesn't need to be restarted when it resumes within yield.

Change-Id: I829c387d6ddb563b2957db47e55adadbbe6bc51a
Reviewed-on: https://gem5-review.googlesource.com/12265
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Use the eq pointer directly less often in the scheduler.

This takes advantage of the utility functions that exist a little
better, and also avoids accidentally asymetrically using
eventsToSchedule and eq->(de)schedule.

Change-Id: I1eb1c228d47684cccb9deaf6f3409b77cfbad4cd
Reviewed-on: https://gem5-review.googlesource.com/12260
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Clear out the scheduler more agressively and with common code.

It's be useful/necessary to flush pending activity even when not
tearing down the scheduler, specifically when stopping.

Change-Id: I6b3716a8ca1f8ca151222e08f30bd3c9a43364b9
Reviewed-on: https://gem5-review.googlesource.com/12248
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Make sure no delta cycles are scheduled when stopping.

If the readyEvent is still scheduled when sc_main completes, gem5 will
return to it's main fiber and keep executing events, including that
one. That means a delta cycle will run even after sc_main is complete.
This change ensures that the readyEvent has been descheduled as part
of stopping.

Change-Id: I9479ac4ebff3335477b371b02efa6d44c70cbc8e
Reviewed-on: https://gem5-review.googlesource.com/12224
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Improve scheduler cleanup.

Make the scheduler clear itself out when it's destructed to ensure that
nobody will try to use it after it's gone away. Also make sure there
are no pending events which might refer to it as well, either systemc
events or gem5 events.

Change-Id: I12dadc06bd9db7016a8dc0c1827b3e630b0d23d5
Reviewed-on: https://gem5-review.googlesource.com/12222
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Generalize gem5 style event scheduling.

These events are either scheduled directly, or if no event queue is
yet available they're recorded in a map to schedule later. Since this
was used in a few places (and should have been used for the ready
event), this change moves it into some common functions which remove
some duplication and abstract away this detail.

Change-Id: I4320d7296f4f72344539b2b4b2564a6a27576dd8
Reviewed-on: https://gem5-review.googlesource.com/12219
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Make sure sc_start waits for simulation even when starving.

Even if the simulation would return from sc_start immediately because
of starvation, this change ensures that sc_start gives control back
to gem5 so that the scheduler will have a chance to set up
sensitivities, etc., before things get torn down.

Change-Id: I39b1fd704fcbe12c299cad9dbd30258e8fe9d032
Reviewed-on: https://gem5-review.googlesource.com/12218
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Rework the init phase for the new way delta notes are handled.

The initialization phase had been done in a somewhat adhoc way,
partially because delta notifications were being handled as top level
gem5 events which were ordered based on their priorities. This change
makes the initialization phase happen more explicitly, and more in the
order in the spec.

Change-Id: I91d56b63fefcb81c845c52c97826a976a7559fad
Reviewed-on: https://gem5-review.googlesource.com/12217
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Don't run the ready event inline when unpausing.

Now that delta events are handled explicitly by the scheduler, there's
no reason to run the readyEvent inline when returning from a pause. The
delta events will necessarily be run after the evaluate and update
phases.

Change-Id: Iad6d431a87742354e3a46a0fb44c309aa785ea60
Reviewed-on: https://gem5-review.googlesource.com/12214
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Rework how delta and timed notifications/timeouts are tracked.

Rather than delegating them entirely to the gem5 event queue and using
priorities to ensure the right thing happens, this change adds a few
new structures which keep track of them and give the scheduler more
control over what happens and in what order. The old scheme was mostly
correct, but there were some competing situations which made it next
to impossible to make everything happen at the right time.

Change-Id: I43f4dd6ddfa488a31073c0318bb41369b1a6117d
Reviewed-on: https://gem5-review.googlesource.com/12213
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: When sc_start is told to run zero time, do one delta cycle.

This is a special case which is mentioned in the spec but hadn't yet
been given any special handling in this implementation.

Change-Id: I500d046f09d916a08e22821f8d3e2f490f8ba5bb
Reviewed-on: https://gem5-review.googlesource.com/12212
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Ensure delta notifications happen at the right time after sc_pause.

Normally delta notifications would be created during the evaluation or
update phases, and so there isn't any problem with them cutting in
front of those stages. When the simulation is paused however, those
notifications could be waiting before the ready event starts and could
preempt it.

This change adds a check for that situation to the end of the pause
event and runs the evalution and update stages inline if necessary.

Change-Id: I4477b2ae8e7980406df00ba7320ae2a24ae2da9b
Reviewed-on: https://gem5-review.googlesource.com/12080
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Don't schedule the update phase if the event queue is null.

That happens when an update is requested before the initialization
phase has started. In that case, the update phase will be manually run
and no event needs to be scheduled, even if that was possible.

Change-Id: I2008e29064d282f82bd1935dbe5b94407aa925b0
Reviewed-on: https://gem5-review.googlesource.com/12078
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Ignore direct requests to mark a process as ready.

That might happen when a process is being marked as ready at the start
of simulation.

Because the process might not end up on the ready list, displacing it
from the init list, excplicitly pop it off the init list as well.

Change-Id: Iebf972e3e1baedec17b9b99b4da9dd44cd8e6957
Reviewed-on: https://gem5-review.googlesource.com/12047
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Fill out process handle kill and reset mechanisms.

Some flags were being updated too early, making the functions think
what they were about to do had already been done. Also, actually check
for and throw the exception installed in a process when it's next
supposed to run, and when injecting an exception schedule that other
process to run immediately.

Change-Id: I0856b69903699b2c66f9dc7f44942bbfe3cfdcc4
Reviewed-on: https://gem5-review.googlesource.com/12046
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement the SC_EXIT_ON_STARVATION exit mode.

This mode implies checking whether there's any activity left either
before starting a delta cycle, or processing delta or timed
notification or timeout.

Change-Id: I0780a1f720cf63f3d2907b8dd28685266b52d6b4
Reviewed-on: https://gem5-review.googlesource.com/12038
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Handle event notifications scheduled before sc_start.

After sc_start is called, gem5 has run far enough to have an event
queue to schedule the notification events on. Before then, it's still
legal to request a timed notification. The scheduler should keep track
of those requests, and once an event queue is available it should
add them to it.

Change-Id: Ie7445b1f2e616f4bd36044a09dbef9e1d12d7350
Reviewed-on: https://gem5-review.googlesource.com/12036
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement the various sc_module stage callbacks.

This change also gets rid of the SystemC namespace which was
deprecated in favor of sc_gem5.

A few utility functions which check whether certain callbacks have
finished were also implemented. status tracking moved from a global
variable in sc_main.cc to a member of the kernel simobject.

Change-Id: I50967fae9c576fbe45b1faff587aaa824857a289
Reviewed-on: https://gem5-review.googlesource.com/12033
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement pending activity related functions

Track the number of notifications/timeouts that are scheduled at any
given time. This lets us implement sc_pending_activity_at_current_time,
sc_pending_activity_at_future_time, and sc_time_to_pending_activity.

Change-Id: Ia3fcd29bdbfe1a6c77eb52ce4836982d4705263c
Reviewed-on: https://gem5-review.googlesource.com/12032
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement sc_pause, sc_stop, and re-sc_start-ing.

This change further modifies the scheduler to implement the sc_pause
and sc_stop functions, and to ensure that calling sc_start again works.
Also, some small changes were made to how processes and contexts are
hooked up. Now, rather than checking whether a process is running to
determine wether it started on its own or needs to be started manually,
there's a bool which explicitly tracks whether it needs this step. The
problem was that once a thread finished, it wasn't considered running
any more. In that case it had run but finished, but that was
indistinguishable from it needing to run but not having been started.

Change-Id: I3aefb5493f91d9efa1a1382586196339b67925fe
Reviewed-on: https://gem5-review.googlesource.com/12031
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Handle suspended processes and handle sensitivity overload.

This change keeps track of whether a process would have become ready
but was suspended so that it can become ready when the process is
resumed.

Also, this makes a process ignore its static sensitivity while a
dynamic sensitivity is in place.

Change-Id: If3f6c62f370051e574f81bf227746db8c43527e2
Reviewed-on: https://gem5-review.googlesource.com/11715
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement the sensitivity mechanism.

This change lets processes be sensitive to events, timeouts, etc.

Change-Id: If30a256dfa8a2e92192c1f9c96b48e2aa28ec27e
Reviewed-on: https://gem5-review.googlesource.com/11713
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Implement channel updates and rework the scheduler.

This change implements channel updates, and also reworks the scheduler
to delegate more to the gem5 event queue by taking advantage of
event priorities to ensure things happen in the right order. There's
a lengthy comment in scheduler.hh describes how that all works.

Change-Id: I5dee71b86b2e612bb720a4429f3a72e4b7c6d01f
Reviewed-on: https://gem5-review.googlesource.com/11710
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

systemc: Partially implement the scheduler.

This change implements the "evaluate" part of the delta cycles, and
sketches out a function to run delta cycles and the initialization
phase. The kernel object now schedules an event at time zero which
runs the initialization phase.

Also, some small places which were stubbed out pending a way to check
the currently running process have been filled in now that that's
being tracked.

Change-Id: I6899569eb0195ff1c059fa4e68e90ef162b2f2df
Reviewed-on: https://gem5-review.googlesource.com/11709
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>