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From: Ian Lance Taylor <ian@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-2903] runtime: portable access to sigev_notify_thread_id Date: Tue, 27 Sep 2022 16:30:59 +0000 (GMT) [thread overview] Message-ID: <20220927163059.8CD163858012@sourceware.org> (raw) 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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