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| author | Austin Clements <austin@google.com> | 2016-10-19 18:27:39 -0400 |
|---|---|---|
| committer | Austin Clements <austin@google.com> | 2016-10-24 02:23:16 +0000 |
| commit | bf9c71cb434a730679f54a3a87c2e9e36ec400d0 (patch) | |
| tree | f90242f9a099f13b49f131e714a6d15779804478 /src/runtime/asm_arm.s | |
| parent | cdccd6a79c5391c21c8e7316e13f8b8d1697ea63 (diff) | |
| download | go-bf9c71cb434a730679f54a3a87c2e9e36ec400d0.tar.gz go-bf9c71cb434a730679f54a3a87c2e9e36ec400d0.zip | |
runtime: make morestack less subtle
morestack writes the context pointer to gobuf.ctxt, but since
morestack is written in assembly (and has to be very careful with
state), it does *not* invoke the requisite write barrier for this
write. Instead, we patch this up later, in newstack, where we invoke
an explicit write barrier for ctxt.
This already requires some subtle reasoning, and it's going to get a
lot hairier with the hybrid barrier.
Fix this by simplifying the whole mechanism. Instead of writing
gobuf.ctxt in morestack, just pass the value of the context register
to newstack and let it write it to gobuf.ctxt. This is a normal Go
pointer write, so it gets the normal Go write barrier. No subtle
reasoning required.
Updates #17503.
Change-Id: Ia6bf8459bfefc6828f53682ade32c02412e4db63
Reviewed-on: https://go-review.googlesource.com/31550
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Diffstat (limited to 'src/runtime/asm_arm.s')
| -rw-r--r-- | src/runtime/asm_arm.s | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/src/runtime/asm_arm.s b/src/runtime/asm_arm.s index 0c7d580163..3bfa250c99 100644 --- a/src/runtime/asm_arm.s +++ b/src/runtime/asm_arm.s @@ -294,10 +294,10 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0 // Called from f. // Set g->sched to context in f. - MOVW R7, (g_sched+gobuf_ctxt)(g) MOVW R13, (g_sched+gobuf_sp)(g) MOVW LR, (g_sched+gobuf_pc)(g) MOVW R3, (g_sched+gobuf_lr)(g) + // newstack will fill gobuf.ctxt. // Called from f. // Set m->morebuf to f's caller. @@ -310,6 +310,9 @@ TEXT runtime·morestack(SB),NOSPLIT,$-4-0 MOVW m_g0(R8), R0 BL setg<>(SB) MOVW (g_sched+gobuf_sp)(g), R13 + MOVW $0, R0 + MOVW.W R0, -8(R13) // create a call frame on g0 + MOVW R7, 4(R13) // ctxt argument BL runtime·newstack(SB) // Not reached, but make sure the return PC from the call to newstack |