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.
Change-Id: I0924a53d5212730ebc395ecf9199f85967be8cc6
Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/434755
Reviewed-by: Cherry Mui <cherryyz@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/libgo/go/runtime/os_linux.go b/libgo/go/runtime/os_linux.go
index 96fb178..2b2d827 100644
--- a/libgo/go/runtime/os_linux.go
+++ b/libgo/go/runtime/os_linux.go
@@ -22,6 +22,12 @@
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 @@
)
// 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 @@
}
// 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 @@
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 528d9b6..aa1b630 100644
--- a/libgo/runtime/go-signal.c
+++ b/libgo/runtime/go-signal.c
@@ -183,6 +183,24 @@
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.
