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runtime: fix GNU/Linux getproccount if sched_getaffinity does not return a multiple of 8

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The current code can potentially return a smaller processor count on a
linux kernel when its cpumask_size (controlled by both kernel config and
boot parameter) is not a multiple of the pointer size, because
r/sys.PtrSize will be rounded down. Since sched_getaffinity returns the
size in bytes, we can just allocate the buf as a byte array to avoid the
extra calculation with the pointer size and roundups.

Change-Id: I0c21046012b88d8a56b5dd3dde1d158d94f8eea9
Reviewed-on: https://go-review.googlesource.com/75591
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This commit is contained in:
Zhengyu He 2017-11-02 13:39:14 -07:00 committed by Ian Lance Taylor
parent 923299a6b8
commit eaf603601b
1 changed files with 3 additions and 3 deletions
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6
src/runtime/os_linux.go
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@ -89,13 +89,13 @@ func getproccount() int32 {
// buffers, but we don't have a dynamic memory allocator at the
// moment, so that's a bit tricky and seems like overkill.
const maxCPUs = 64 * 1024
var buf [maxCPUs / (sys.PtrSize * 8)]uintptr
var buf [maxCPUs / 8]byte
r := sched_getaffinity(0, unsafe.Sizeof(buf), &buf[0])
if r < 0 {
return 1
}
n := int32(0)
for _, v := range buf[:r/sys.PtrSize] {
for _, v := range buf[:r] {
for v != 0 {
n += int32(v & 1)
v >>= 1
@ -385,7 +385,7 @@ func raise(sig uint32)
func raiseproc(sig uint32)
//go:noescape
func sched_getaffinity(pid, len uintptr, buf *uintptr) int32
func sched_getaffinity(pid, len uintptr, buf *byte) int32
func osyield()
//go:nosplit