The sampler from the Gecko profiler can interrupt compaction.

This showed up on my try runs for bug 1263355. Needless to say I don't know how to write a test case for this for tip. Does this pointer also need to be updated after compaction? The only place where ProfileEntry::trace is called is in markRuntime, which is during root marking.

This should do it.

Comment on attachment 8781756 [details] [diff] [review] Use MaybeForwarded in ProfileEntry::script. Review of attachment 8781756 [details] [diff] [review]: ----------------------------------------------------------------- This looks like it will work to me. Forwarding to Jon for the more general question of what needs to happen for roots after CGC.

Comment on attachment 8781756 [details] [diff] [review] Use MaybeForwarded in ProfileEntry::script. Review of attachment 8781756 [details] [diff] [review]: ----------------------------------------------------------------- Thanks for fixing this shu. markRuntime is also called during compacting to update the roots, so the fixupAfterMovingGC part is not required.

Is the relocation overlay written atomically? Assuming it is not: What happens if the SIGPROF is triggered when the relocation overlay is only partially written? How will MaybeForwarded and the updated pseudo stack code handle this case? Perhaps, this is a naive question, in which case I would love an explanation as to why that is :)

(In reply to Nick Fitzgerald [:fitzgen] [⏰PDT; UTC-7] from comment #5) > Is the relocation overlay written atomically? > > Assuming it is not: What happens if the SIGPROF is triggered when the > relocation overlay is only partially written? How will MaybeForwarded and > the updated pseudo stack code handle this case? > > Perhaps, this is a naive question, in which case I would love an explanation > as to why that is :) You're right. From our IRC convo I don't have a better solution than AutoSuppressProfilerSampling. The moving is also a problem for the JitcodeGlobalTable. Sampling must be suppressed from the time the first JSScript is moved until both the SPS stack and JitcodeGlobalTable are forwarded. :(

In light of fitzgen's comment 5, I'm gonna put the hammer down until we find something better.

Pushed by shu@rfrn.org: https://hg.mozilla.org/integration/mozilla-inbound/rev/121757de3a7d Suppress sampling during compaction. (r=djvj)