| commit | ee330385ca684f7c166913e10998f791d1be06e7 | [log] [tgz] |
|---|---|---|
| author | Cherry Zhang <cherryyz@google.com> | Wed Nov 20 17:10:34 2019 -0500 |
| committer | Cherry Zhang <cherryyz@google.com> | Wed May 06 15:41:12 2020 +0000 |
| tree | 63f9b19a0811656bb78fc35df4ad2c7ced36a49d | |
| parent | 4daf8719e7f4c71a620f650d73caab2a9d7ea499 [diff] |
cmd/internal/obj, runtime: preempt & restart some instruction sequences On some architectures, for async preemption the injected call needs to clobber a register (usually REGTMP) in order to return to the preempted function. As a consequence, the PC ranges where REGTMP is live are not preemptible. The uses of REGTMP are usually generated by the assembler, where it needs to load or materialize a large constant or offset that doesn't fit into the instruction. In those cases, REGTMP is not live at the start of the instruction sequence. Instead of giving up preemption in those cases, we could preempt it and restart the sequence when resuming the execution. Basically, this is like reissuing an interrupted instruction, except that here the "instruction" is a Prog that consists of multiple machine instructions. For this to work, we need to generate PC data to mark the start of the Prog. Currently this is only done for ARM64. TODO: the split-stack function prologue is currently not async preemptible. We could use this mechanism, preempt it and restart at the function entry. Change-Id: I37cb282f8e606e7ab6f67b3edfdc6063097b4bd1 Reviewed-on: https://go-review.googlesource.com/c/go/+/208126 Run-TryBot: Cherry Zhang <cherryyz@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Austin Clements <austin@google.com>
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