From ccd992355df7192993c666236047820244914598 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Tue, 16 Apr 2024 21:19:13 +0200 Subject: Adding upstream version 1.21.8. Signed-off-by: Daniel Baumann --- src/runtime/testdata/testprog/lockosthread.go | 246 ++++++++++++++++++++++++++ 1 file changed, 246 insertions(+) create mode 100644 src/runtime/testdata/testprog/lockosthread.go (limited to 'src/runtime/testdata/testprog/lockosthread.go') diff --git a/src/runtime/testdata/testprog/lockosthread.go b/src/runtime/testdata/testprog/lockosthread.go new file mode 100644 index 0000000..90d98e4 --- /dev/null +++ b/src/runtime/testdata/testprog/lockosthread.go @@ -0,0 +1,246 @@ +// Copyright 2017 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +package main + +import ( + "os" + "runtime" + "sync" + "time" +) + +var mainTID int + +func init() { + registerInit("LockOSThreadMain", func() { + // init is guaranteed to run on the main thread. + mainTID = gettid() + }) + register("LockOSThreadMain", LockOSThreadMain) + + registerInit("LockOSThreadAlt", func() { + // Lock the OS thread now so main runs on the main thread. + runtime.LockOSThread() + }) + register("LockOSThreadAlt", LockOSThreadAlt) + + registerInit("LockOSThreadAvoidsStatePropagation", func() { + // Lock the OS thread now so main runs on the main thread. + runtime.LockOSThread() + }) + register("LockOSThreadAvoidsStatePropagation", LockOSThreadAvoidsStatePropagation) + register("LockOSThreadTemplateThreadRace", LockOSThreadTemplateThreadRace) +} + +func LockOSThreadMain() { + // gettid only works on Linux, so on other platforms this just + // checks that the runtime doesn't do anything terrible. + + // This requires GOMAXPROCS=1 from the beginning to reliably + // start a goroutine on the main thread. + if runtime.GOMAXPROCS(-1) != 1 { + println("requires GOMAXPROCS=1") + os.Exit(1) + } + + ready := make(chan bool, 1) + go func() { + // Because GOMAXPROCS=1, this *should* be on the main + // thread. Stay there. + runtime.LockOSThread() + if mainTID != 0 && gettid() != mainTID { + println("failed to start goroutine on main thread") + os.Exit(1) + } + // Exit with the thread locked, which should exit the + // main thread. + ready <- true + }() + <-ready + time.Sleep(1 * time.Millisecond) + // Check that this goroutine is still running on a different + // thread. + if mainTID != 0 && gettid() == mainTID { + println("goroutine migrated to locked thread") + os.Exit(1) + } + println("OK") +} + +func LockOSThreadAlt() { + // This is running locked to the main OS thread. + + var subTID int + ready := make(chan bool, 1) + go func() { + // This goroutine must be running on a new thread. + runtime.LockOSThread() + subTID = gettid() + ready <- true + // Exit with the thread locked. + }() + <-ready + runtime.UnlockOSThread() + for i := 0; i < 100; i++ { + time.Sleep(1 * time.Millisecond) + // Check that this goroutine is running on a different thread. + if subTID != 0 && gettid() == subTID { + println("locked thread reused") + os.Exit(1) + } + exists, supported := tidExists(subTID) + if !supported || !exists { + goto ok + } + } + println("sub thread", subTID, "still running") + return +ok: + println("OK") +} + +func LockOSThreadAvoidsStatePropagation() { + // This test is similar to LockOSThreadAlt in that it will detect if a thread + // which should have died is still running. However, rather than do this with + // thread IDs, it does this by unsharing state on that thread. This way, it + // also detects whether new threads were cloned from the dead thread, and not + // from a clean thread. Cloning from a locked thread is undesirable since + // cloned threads will inherit potentially unwanted OS state. + // + // unshareFs, getcwd, and chdir("/tmp") are only guaranteed to work on + // Linux, so on other platforms this just checks that the runtime doesn't + // do anything terrible. + // + // This is running locked to the main OS thread. + + // GOMAXPROCS=1 makes this fail much more reliably if a tainted thread is + // cloned from. + if runtime.GOMAXPROCS(-1) != 1 { + println("requires GOMAXPROCS=1") + os.Exit(1) + } + + if err := chdir("/"); err != nil { + println("failed to chdir:", err.Error()) + os.Exit(1) + } + // On systems other than Linux, cwd == "". + cwd, err := getcwd() + if err != nil { + println("failed to get cwd:", err.Error()) + os.Exit(1) + } + if cwd != "" && cwd != "/" { + println("unexpected cwd", cwd, " wanted /") + os.Exit(1) + } + + ready := make(chan bool, 1) + go func() { + // This goroutine must be running on a new thread. + runtime.LockOSThread() + + // Unshare details about the FS, like the CWD, with + // the rest of the process on this thread. + // On systems other than Linux, this is a no-op. + if err := unshareFs(); err != nil { + if err == errNotPermitted { + println("unshare not permitted") + os.Exit(0) + } + println("failed to unshare fs:", err.Error()) + os.Exit(1) + } + // Chdir to somewhere else on this thread. + // On systems other than Linux, this is a no-op. + if err := chdir(os.TempDir()); err != nil { + println("failed to chdir:", err.Error()) + os.Exit(1) + } + + // The state on this thread is now considered "tainted", but it + // should no longer be observable in any other context. + + ready <- true + // Exit with the thread locked. + }() + <-ready + + // Spawn yet another goroutine and lock it. Since GOMAXPROCS=1, if + // for some reason state from the (hopefully dead) locked thread above + // propagated into a newly created thread (via clone), or that thread + // is actually being re-used, then we should get scheduled on such a + // thread with high likelihood. + done := make(chan bool) + go func() { + runtime.LockOSThread() + + // Get the CWD and check if this is the same as the main thread's + // CWD. Every thread should share the same CWD. + // On systems other than Linux, wd == "". + wd, err := getcwd() + if err != nil { + println("failed to get cwd:", err.Error()) + os.Exit(1) + } + if wd != cwd { + println("bad state from old thread propagated after it should have died") + os.Exit(1) + } + <-done + + runtime.UnlockOSThread() + }() + done <- true + runtime.UnlockOSThread() + println("OK") +} + +func LockOSThreadTemplateThreadRace() { + // This test attempts to reproduce the race described in + // golang.org/issue/38931. To do so, we must have a stop-the-world + // (achieved via ReadMemStats) racing with two LockOSThread calls. + // + // While this test attempts to line up the timing, it is only expected + // to fail (and thus hang) around 2% of the time if the race is + // present. + + // Ensure enough Ps to actually run everything in parallel. Though on + // <4 core machines, we are still at the whim of the kernel scheduler. + runtime.GOMAXPROCS(4) + + go func() { + // Stop the world; race with LockOSThread below. + var m runtime.MemStats + for { + runtime.ReadMemStats(&m) + } + }() + + // Try to synchronize both LockOSThreads. + start := time.Now().Add(10 * time.Millisecond) + + var wg sync.WaitGroup + wg.Add(2) + + for i := 0; i < 2; i++ { + go func() { + for time.Now().Before(start) { + } + + // Add work to the local runq to trigger early startm + // in handoffp. + go func() {}() + + runtime.LockOSThread() + runtime.Gosched() // add a preemption point. + wg.Done() + }() + } + + wg.Wait() + // If both LockOSThreads completed then we did not hit the race. + println("OK") +} -- cgit v1.2.3