When run on cooperative threads, we need to notify the threading system
when we're going to block (in any way, sleep or spin) so that it doesn't
wake that thread up expecting it to make forward progress.
This should cover SkOnce, SkSpinlock, SkSemaphore, and by extension
SkMutex. Not sure if there are others to hit, but really the only way
to find out is by deadlocked stack traces. This CL (obviously?) does
nothing to mark synchronization primitives used by Skia's dependencies,
and in general I don't think we can do anything about them.
See cr/275261423 for more background and discussion. It's not clear to
me that marking these symbols as weak is necessary, so I figured I'd
just try not doing that and seeing what breaks. I can always follow up
with weak symbols if proven necessary.
Bug: skia:9577
Change-Id: I2c03fe92c58ad506dd8a68bdc90a09b28f965149
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/251221
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
a1991f5e3b