This change fixes a race condition between beforeIdle waking up the
innermost event handler and a timer causing a different goroutine to
wake up at the exact same moment. This messes up the wasm event handling
and leads to memory corruption. The solution is to make beforeIdle
return the goroutine that must run next and have findrunnable pick
this goroutine without considering timers again.
Fixes#38093Fixes#38574
Change-Id: Iffbe99411d25c2730953d1c8b0741fd892f8e540
Reviewed-on: https://go-review.googlesource.com/c/go/+/230178
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
I added routines that can acquire/release a particular rank without
acquiring/releasing an associated lock. I added lockRankGscan as a rank
for acquiring/releasing the Gscan bit.
castogscanstatus() and casGtoPreemptScan() are acquires of the Gscan
bit. casfrom_Gscanstatus() is a release of the Gscan bit. casgstatus()
is like an acquire and release of the Gscan bit, since it will wait if
Gscan bit is currently set.
We have a cycle between hchan and Gscan. The acquisition of Gscan and
then hchan only happens in syncadjustsudogs() when the G is suspended,
so the main normal ordering (get hchan, then get Gscan) can't be
happening. So, I added a new rank lockRankHchanLeaf that is used when
acquiring hchan locks in syncadjustsudogs. This ranking is set so no
other locks can be acquired except other hchan locks.
Fixes#38922
Change-Id: I58ce526a74ba856cb42078f7b9901f2832e1d45c
Reviewed-on: https://go-review.googlesource.com/c/go/+/228417
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
I took some of the infrastructure from Austin's lock logging CR
https://go-review.googlesource.com/c/go/+/192704 (with deadlock
detection from the logs), and developed a setup to give static lock
ranking for runtime locks.
Static lock ranking establishes a documented total ordering among locks,
and then reports an error if the total order is violated. This can
happen if a deadlock happens (by acquiring a sequence of locks in
different orders), or if just one side of a possible deadlock happens.
Lock ordering deadlocks cannot happen as long as the lock ordering is
followed.
Along the way, I found a deadlock involving the new timer code, which Ian fixed
via https://go-review.googlesource.com/c/go/+/207348, as well as two other
potential deadlocks.
See the constants at the top of runtime/lockrank.go to show the static
lock ranking that I ended up with, along with some comments. This is
great documentation of the current intended lock ordering when acquiring
multiple locks in the runtime.
I also added an array lockPartialOrder[] which shows and enforces the
current partial ordering among locks (which is embedded within the total
ordering). This is more specific about the dependencies among locks.
I don't try to check the ranking within a lock class with multiple locks
that can be acquired at the same time (i.e. check the ranking when
multiple hchan locks are acquired).
Currently, I am doing a lockInit() call to set the lock rank of most
locks. Any lock that is not otherwise initialized is assumed to be a
leaf lock (a very high rank lock), so that eliminates the need to do
anything for a bunch of locks (including all architecture-dependent
locks). For two locks, root.lock and notifyList.lock (only in the
runtime/sema.go file), it is not as easy to do lock initialization, so
instead, I am passing the lock rank with the lock calls.
For Windows compilation, I needed to increase the StackGuard size from
896 to 928 because of the new lock-rank checking functions.
Checking of the static lock ranking is enabled by setting
GOEXPERIMENT=staticlockranking before doing a run.
To make sure that the static lock ranking code has no overhead in memory
or CPU when not enabled by GOEXPERIMENT, I changed 'go build/install' so
that it defines a build tag (with the same name) whenever any experiment
has been baked into the toolchain (by checking Expstring()). This allows
me to avoid increasing the size of the 'mutex' type when static lock
ranking is not enabled.
Fixes#38029
Change-Id: I154217ff307c47051f8dae9c2a03b53081acd83a
Reviewed-on: https://go-review.googlesource.com/c/go/+/207619
Reviewed-by: Dan Scales <danscales@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Because of concurrent goroutines it is possible for multiple event
handlers to return at the same time. This was not properly supported
and caused the wrong goroutine to continue, which in turn caused
memory corruption.
This change adds a stack of events so it is always clear which is the
innermost event that needs to return next.
Fixes#35256
Change-Id: Ia527da3b91673bc14e84174cdc407f5c9d5a3d09
Reviewed-on: https://go-review.googlesource.com/c/go/+/204662
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
When we put timers on P's, the wasm code will not be able to rely on
the timer goroutine. Use the beforeIdle hook to schedule a wakeup.
Updates #6239
Updates #27707
Change-Id: Idf6309944778b8c3d7178f5d09431940843ea233
Reviewed-on: https://go-review.googlesource.com/c/go/+/171827
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
An extra goroutine is necessary to handle asynchronous events on wasm.
However, we do not want this goroutine to exist all the time.
This change makes it short-lived, so it ends after the asynchronous
event was handled.
Fixes#34768
Change-Id: I24626ff0af9d803a01ebe33fbb584d04d2059a44
Reviewed-on: https://go-review.googlesource.com/c/go/+/200497
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
On wasm there is a special goroutine that handles asynchronous events.
Blocking this goroutine often causes a deadlock. However, the stack
trace of this goroutine was omitted when printing the deadlock error.
This change adds an exception so the goroutine is not considered as
an internal system goroutine and the stack trace gets printed, which
helps with debugging the deadlock.
Updates #32764
Change-Id: Icc8f5ba3ca5a485d557b7bdd76bf2f1ffb92eb3e
Reviewed-on: https://go-review.googlesource.com/c/go/+/199537
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Trybots started failing on js/wasm after golang.org/cl/175797 landed,
but it seemed completely unrelated. It would fail very consistently on
the heapsampling.go test.
Digging deeper it was very difficult to ascertain what was going wrong,
but clearly m.locks for some m was non-zero when calling into the
scheduler.
The failure comes from the fact that lock calls into gosched, but it's
unclear how exactly we got there in the first place; there should be no
preemption in this single-threaded context.
Furthermore, lock shouldn't be calling gosched_m at all because in a
single-threaded context, the thread shouldn't be preempted until it
actually unlocks.
But, digging further it turns out the implementation in lock_js.go never
incremented or decremented m.locks. This is definitely wrong because
many parts of the runtime depend on that value being set correctly.
So, this change removes the loop which calls into gosched_m (which
should be unnecessary) and increments and decrements m.locks
appropriately. This appears to fix the aforementioned failure.
Change-Id: Id214c0762c3fb2b405ff55543d7e2a78c17443c4
Reviewed-on: https://go-review.googlesource.com/c/go/+/176297
Run-TryBot: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
A notetsleepg may get stuck if its timeout callback gets invoked
exactly on its deadline due to low precision of nanotime. This change
fixes the comparison so it also resolves the note if the timestamps are
equal.
Updates #28975
Change-Id: I045d2f48b7f41cea0caec19b56876e9de01dcd6c
Reviewed-on: https://go-review.googlesource.com/c/153558
Run-TryBot: Richard Musiol <neelance@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The name "Callback" does not fit to all use cases of js.Callback.
This commit changes its name to Func. Accordingly NewCallback
gets renamed to FuncOf, which matches ValueOf and TypedArrayOf.
The package syscall/js is currently exempt from Go's compatibility
promise and js.Callback is already affected by a breaking change in
this release cycle. See #28711 for details.
Fixes#28711
Change-Id: I2c380970c3822bed6a3893909672c15d0cbe9da3
Reviewed-on: https://go-review.googlesource.com/c/153559
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
With this change, callbacks returned by syscall/js.NewCallback
get executed synchronously. This is necessary for the APIs of
many JavaScript libraries.
A callback triggered during a call from Go to JavaScript gets executed
on the same goroutine. A callback triggered by JavaScript's event loop
gets executed on an extra goroutine.
Fixes#26045Fixes#27441
Change-Id: I591b9e85ab851cef0c746c18eba95fb02ea9e85b
Reviewed-on: https://go-review.googlesource.com/c/142004
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit adds support for JavaScript callbacks back into
WebAssembly. This is experimental API, just like the rest of the
syscall/js package. The time package now also uses this mechanism
to properly support timers without resorting to a busy loop.
JavaScript code can call into the same entry point multiple times.
The new RUN register is used to keep track of the program's
run state. Possible values are: starting, running, paused and exited.
If no goroutine is ready any more, the scheduler can put the
program into the "paused" state and the WebAssembly code will
stop running. When a callback occurs, the JavaScript code puts
the callback data into a queue and then calls into WebAssembly
to allow the Go code to continue running.
Updates #18892
Updates #25506
Change-Id: Ib8701cfa0536d10d69bd541c85b0e2a754eb54fb
Reviewed-on: https://go-review.googlesource.com/114197
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Richard Musiol
Dan Scales
Ian Lance Taylor
Michael Anthony Knyszek