This reverts commit dfb3f7daa5.
Reason for revert: Breaks LSAN & ASAN flakily: https://bugs.chromium.org/p/v8/issues/detail?id=10861
Original change's description:
> [cpu-profiler] Ensure sampled thread has Isolate lock under Windows
>
> While the sampler checked if the sampled thread had the Isolate locked
> (if locks are being used) under Linux, the check was not done under
> Windows (or Fuchsia) which meant that in a multi-threading application
> under Windows, thread locking was not checked making it prone to seg
> faults and the like as the profiler would be extracting info from a
> heap in motion. The fix was to move the lock check into CpuSampler
> and Ticker (--prof) so all OSes would do the correct check.
>
> The basic concept is that on all operating systems a CpuProfiler, and
> so its corresponding CpuCampler, the profiler is tied to a thread.
> This is not based on first principles or anything, it's simply the
> way it works in V8, though it is a useful conceit as it makes
> visualization and interpretation of profile data much easier.
>
> To collect a sample on a thread associated with a profiler the thread
> must be stopped for obvious reasons -- walking the stack of a running
> thread is a formula for disaster. The mechanism for stopping a thread
> is OS-specific and is done in sample.cc. There are currently three
> basic approaches, one for Linux/Unix variants, one for Windows and one
> for Fuchsia. The approaches vary as to which thread actually collects
> the sample -- under Linux the sample is actually collected on the
> (interrupted) sampled thread whereas under Fuchsia/Windows it's on
> a separate thread.
>
> However, in a multi-threaded environment (where Locker is used), it's
> not sufficient for the sampled thread to be stopped. Because the stack
> walk involves looking in the Isolate heap, no other thread can be
> messing with the heap while the sample is collected. The only ways to
> ensure this would be to either stop all threads whenever collecting a
> sample, or to ensure that the thread being sampled holds the Isolate
> lock so prevents other threads from messing with the heap. While there
> might be something to be said for the "stop all threads" approach, the
> current approach in V8 is to only stop the sampled thread so, if in a
> multi-threaded environment, the profiler must check if the thread being
> sampled holds the Isolate lock.
>
> Since this check must be done, independent of which thread the sample
> is being collected on (since it varies from OS to OS), the approach is
> to save the thread id of the thread to be profiled/sampled when the
> CpuSampler is instantiated (on all OSes it is instantiated on the
> sampled thread) and then check that thread id against the Isolate lock
> holder thread id before collecting a sample. If it matches, we know
> sample.cc has stop the sampled thread, one way or another, and we know
> that no other thread can mess with the heap (since the stopped thread
> holds the Isolate lock) so it's safe to walk the stack and collect data
> from the heap so the sample can be taken. It it doesn't match, we can't
> safely collect the sample so we don't.
>
> Bug: v8:10850
> Change-Id: Iab2493130b9328430d7e5f5d3cf90ad6d10b1892
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2377108
> Reviewed-by: Peter Marshall <petermarshall@chromium.org>
> Commit-Queue: Peter Marshall <petermarshall@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#69623}
TBR=akodat@rocketsoftware.com,petermarshall@chromium.org,petermarshall@google.com
Change-Id: Ib6b6dc4ce109d5aa4e504fa7c9769f5cd95ddd0c
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: v8:10850
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2387570
Reviewed-by: Peter Marshall <petermarshall@chromium.org>
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69638}
3243506267