| commit | 835c83b40dd9b94b51180898551b313a92892ffd | [log] [tgz] |
|---|---|---|
| author | Austin Clements <austin@google.com> | Mon Nov 16 15:20:59 2015 -0500 |
| committer | Austin Clements <austin@google.com> | Mon Nov 16 22:07:37 2015 +0000 |
| tree | 352f45ab0db06f4c4f9ac3bdc2f25ce8ffbe563e | |
| parent | 45d1c8ab59cd08ef4a7976f44c8c19ed53b118f8 [diff] |
runtime: clear tiny alloc cache in mark term, not sweep term The tiny alloc cache is maintained in a pointer from non-GC'd memory (mcache) to heap memory and hence must be handled carefully. Currently we clear the tiny alloc cache during sweep termination and, if it is assigned to a non-nil value during concurrent marking, we depend on a write barrier to keep the new value alive. However, while the compiler currently always generates this write barrier, we're treading on thin ice because write barriers may not happen for writes to non-heap memory (e.g., typedmemmove). Without this lucky write barrier, the GC may free a current tiny block while it's still reachable by the tiny allocator, leading to later memory corruption. Change this code so that, rather than depending on the write barrier, we simply clear the tiny cache during mark termination when we're clearing all of the other mcaches. If the current tiny block is reachable from regular pointers, it will be retained; if it isn't reachable from regular pointers, it may be freed, but that's okay because there won't be any pointers in non-GC'd memory to it. Change-Id: I8230980d8612c35c2997b9705641a1f9f865f879 Reviewed-on: https://go-review.googlesource.com/16962 Run-TryBot: Austin Clements <austin@google.com> Reviewed-by: Russ Cox <rsc@golang.org> Reviewed-by: Keith Randall <khr@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
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