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* [gcc r13-2903] runtime: portable access to sigev_notify_thread_id
@ 2022-09-27 16:30 Ian Lance Taylor
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From: Ian Lance Taylor @ 2022-09-27 16:30 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:e73d9fcafbd07bc3714fbaf8a82db71d50015c92
commit r13-2903-ge73d9fcafbd07bc3714fbaf8a82db71d50015c92
Author: Ian Lance Taylor <iant@golang.org>
Date: Mon Sep 26 15:03:53 2022 -0400
runtime: portable access to sigev_notify_thread_id
Previously, libgo relied on the _sigev_un implementation-specific
field in struct sigevent, which is only available on glibc.
This patch uses the sigev_notify_thread_id macro instead which is
mandated by timer_create(2). In theory, this should work with any libc
implementation for Linux. Unfortunately, there is an open glibc bug
as glibc does not define this macro. For this reason, a glibc-specific
workaround is required. Other libcs (such as musl) define the macro
and don't require the workaround.
See https://sourceware.org/bugzilla/show_bug.cgi?id=27417
This makes libgo compatible with musl libc.
Based on patch by Sören Tempel.
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/434755
Diff:
---
gcc/go/gofrontend/MERGE | 2 +-
libgo/go/runtime/os_linux.go | 12 +++++++++++-
libgo/runtime/go-signal.c | 18 ++++++++++++++++++
3 files changed, 30 insertions(+), 2 deletions(-)
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 73aa712dbdf..4793c821eba 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-0140cca9bc0fad1108c7ed369376ac71cc4bfecf
+8f1a91aeff400d572857895b7f5e863ec5a4d93e
The first line of this file holds the git revision number of the last
merge done from the gofrontend repository.
diff --git a/libgo/go/runtime/os_linux.go b/libgo/go/runtime/os_linux.go
index 96fb178870e..2b2d827cee8 100644
--- a/libgo/go/runtime/os_linux.go
+++ b/libgo/go/runtime/os_linux.go
@@ -22,6 +22,12 @@ type mOS struct {
profileTimerValid uint32
}
+// setSigeventTID is written in C to set the sigev_notify_thread_id
+// field of a sigevent struct.
+//
+//go:noescape
+func setSigeventTID(*_sigevent, int32)
+
func getProcID() uint64 {
return uint64(gettid())
}
@@ -52,9 +58,12 @@ const (
)
// Atomically,
+//
// if(*addr == val) sleep
+//
// Might be woken up spuriously; that's allowed.
// Don't sleep longer than ns; ns < 0 means forever.
+//
//go:nosplit
func futexsleep(addr *uint32, val uint32, ns int64) {
// Some Linux kernels have a bug where futex of
@@ -73,6 +82,7 @@ func futexsleep(addr *uint32, val uint32, ns int64) {
}
// If any procs are sleeping on addr, wake up at most cnt.
+//
//go:nosplit
func futexwakeup(addr *uint32, cnt uint32) {
ret := futex(unsafe.Pointer(addr), _FUTEX_WAKE_PRIVATE, cnt, nil, nil, 0)
@@ -365,7 +375,7 @@ func setThreadCPUProfiler(hz int32) {
var sevp _sigevent
sevp.sigev_notify = _SIGEV_THREAD_ID
sevp.sigev_signo = _SIGPROF
- *((*int32)(unsafe.Pointer(&sevp._sigev_un))) = int32(mp.procid)
+ setSigeventTID(&sevp, int32(mp.procid))
ret := timer_create(_CLOCK_THREAD_CPUTIME_ID, &sevp, &timerid)
if ret != 0 {
// If we cannot create a timer for this M, leave profileTimerValid false
diff --git a/libgo/runtime/go-signal.c b/libgo/runtime/go-signal.c
index 528d9b6d9fe..aa1b6305ad0 100644
--- a/libgo/runtime/go-signal.c
+++ b/libgo/runtime/go-signal.c
@@ -183,6 +183,24 @@ setSigactionHandler(struct sigaction* sa, uintptr handler)
sa->sa_sigaction = (void*)(handler);
}
+#ifdef __linux__
+
+// Workaround for https://sourceware.org/bugzilla/show_bug.cgi?id=27417
+#ifndef sigev_notify_thread_id
+ #define sigev_notify_thread_id _sigev_un._tid
+#endif
+
+void setSigeventTID(struct sigevent*, int32_t)
+ __asm__ (GOSYM_PREFIX "runtime.setSigeventTID");
+
+void
+setSigeventTID(struct sigevent *sev, int32_t v)
+{
+ sev->sigev_notify_thread_id = v;
+}
+
+#endif // defined(__linux__)
+
// C code to fetch values from the siginfo_t and ucontext_t pointers
// passed to a signal handler.
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