From 001a75a74c4a27901b0b536efe1be581612c52a9 Mon Sep 17 00:00:00 2001 From: Shawn Walker-Salas Date: Tue, 18 Aug 2015 14:13:38 -0700 Subject: [PATCH] runtime/trace: fix tracing of blocking system calls The placement and invocation of traceGoSysCall when using entersyscallblock() instead of entersyscall() differs enough that the TestTraceSymbolize test can fail on some platforms. This change moves the invocation of traceGoSysCall for entersyscall() so that the same number of "frames to skip" are present in the trace as when entersyscallblock() is used ensuring system call traces remain identical regardless of internal implementation choices. Fixes golang/go#12056 Change-Id: I8361e91aa3708f5053f98263dfe9feb8c5d1d969 Reviewed-on: https://go-review.googlesource.com/13861 Run-TryBot: Dmitry Vyukov Reviewed-by: Dmitry Vyukov --- src/runtime/proc1.go | 12 ++++++++---- src/runtime/trace.go | 2 +- 2 files changed, 9 insertions(+), 5 deletions(-) diff --git a/src/runtime/proc1.go b/src/runtime/proc1.go index 35d9e86e8e..4ffe11b653 100644 --- a/src/runtime/proc1.go +++ b/src/runtime/proc1.go @@ -1823,10 +1823,6 @@ func reentersyscall(pc, sp uintptr) { // but can have inconsistent g->sched, do not let GC observe it. _g_.m.locks++ - if trace.enabled { - systemstack(traceGoSysCall) - } - // Entersyscall must not call any function that might split/grow the stack. // (See details in comment above.) // Catch calls that might, by replacing the stack guard with something that @@ -1846,6 +1842,14 @@ func reentersyscall(pc, sp uintptr) { }) } + if trace.enabled { + systemstack(traceGoSysCall) + // systemstack itself clobbers g.sched.{pc,sp} and we might + // need them later when the G is genuinely blocked in a + // syscall + save(pc, sp) + } + if atomicload(&sched.sysmonwait) != 0 { // TODO: fast atomic systemstack(entersyscall_sysmon) save(pc, sp) diff --git a/src/runtime/trace.go b/src/runtime/trace.go index 29600b5c4d..6631bc29d1 100644 --- a/src/runtime/trace.go +++ b/src/runtime/trace.go @@ -828,7 +828,7 @@ func traceGoUnpark(gp *g, skip int) { } func traceGoSysCall() { - traceEvent(traceEvGoSysCall, 4) + traceEvent(traceEvGoSysCall, 1) } func traceGoSysExit(seq uint64, ts int64) {