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runtime: tidy Context allocation

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The Context object we pass to GetThreadContext on Windows must be 16
byte-aligned. We also can't allocate in the contexts where we create
these, so they must be stack-allocated. There's no great way to do
this, but this CL makes the code at least a little clearer, and makes
profilem and preemptM more consistent with each other.

Change-Id: I5ec47a27d7580ed6003030bf953e668e8cae2cef
Reviewed-on: https://go-review.googlesource.com/c/go/+/207967
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
This commit is contained in:
Austin Clements 2019-11-19 14:48:17 -05:00
parent b89f4c6720
commit 2a029b3f26
1 changed files with 9 additions and 10 deletions
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19
src/runtime/os_windows.go
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@ -1027,17 +1027,17 @@ func callbackasm1()
var profiletimer uintptr
func profilem(mp *m, thread uintptr) {
var r *context
rbuf := make([]byte, unsafe.Sizeof(*r)+15)
// Align Context to 16 bytes.
var c *context
var cbuf [unsafe.Sizeof(*c) + 15]byte
c = (*context)(unsafe.Pointer((uintptr(unsafe.Pointer(&cbuf[15]))) &^ 15))
// align Context to 16 bytes
r = (*context)(unsafe.Pointer((uintptr(unsafe.Pointer(&rbuf[15]))) &^ 15))
r.contextflags = _CONTEXT_CONTROL
stdcall2(_GetThreadContext, thread, uintptr(unsafe.Pointer(r)))
c.contextflags = _CONTEXT_CONTROL
stdcall2(_GetThreadContext, thread, uintptr(unsafe.Pointer(c)))
gp := gFromTLS(mp)
sigprof(r.ip(), r.sp(), r.lr(), gp, mp)
sigprof(c.ip(), c.sp(), c.lr(), gp, mp)
}
func gFromTLS(mp *m) *g {
@ -1153,10 +1153,9 @@ func preemptM(mp *m) {
stdcall7(_DuplicateHandle, currentProcess, mp.thread, currentProcess, uintptr(unsafe.Pointer(&thread)), 0, 0, _DUPLICATE_SAME_ACCESS)
unlock(&mp.threadLock)
// Prepare thread context buffer.
// Prepare thread context buffer. This must be aligned to 16 bytes.
var c *context
cbuf := make([]byte, unsafe.Sizeof(*c)+15)
// Align Context to 16 bytes.
var cbuf [unsafe.Sizeof(*c) + 15]byte
c = (*context)(unsafe.Pointer((uintptr(unsafe.Pointer(&cbuf[15]))) &^ 15))
c.contextflags = _CONTEXT_CONTROL