feat: Waku v2 bridge

Issue #12610

vendor/github.com/anacrolix/sync/sync.go

@@ -0,0 +1,92 @@
+// Package sync is an extension of the stdlib "sync" package. It has extra
+// functionality that helps debug the use of synchronization primitives. The
+// package should be importable in place of "sync". The extra functionality
+// can be enabled by calling Enable() or passing a non-empty PPROF_SYNC
+// environment variable to the process.
+//
+// Several profiles are exposed on the default HTTP muxer (and to
+// "/debug/pprof" when "net/http/pprof" is imported by the process).
+// "lockHolders" lists the stack traces of goroutines that called Mutex.Lock
+// that haven't subsequently been Unlocked. "lockBlockers" contains goroutines
+// that are waiting to obtain locks. "/debug/lockTimes" or PrintLockTimes()
+// shows the longest time a lock is held for each stack trace.
+//
+// Note that currently RWMutex is treated like a Mutex when the package is
+// enabled.
+package sync
+
+import (
+	"fmt"
+	"io"
+	"net/http"
+	"os"
+	"runtime/pprof"
+	"strings"
+	"sync"
+	"text/tabwriter"
+
+	"github.com/anacrolix/missinggo"
+)
+
+var (
+	// Protects initialization and enabling of the package.
+	enableMu sync.Mutex
+	// Whether shared locks must be handled as exclusive locks.
+	noSharedLocking = false
+	contentionOn    = false
+	lockTimesOn     = false
+	// Current lock holders.
+	lockHolders *pprof.Profile
+	// Those blocked on acquiring a lock.
+	lockBlockers *pprof.Profile
+)
+
+// Writes out the longest time a Mutex remains locked for each stack trace
+// that locks a Mutex.
+func PrintLockTimes(w io.Writer) {
+	lockTimes := sortedLockTimes()
+	tw := tabwriter.NewWriter(w, 1, 8, 1, '\t', 0)
+	defer tw.Flush()
+	w = tw
+	for _, elem := range lockTimes {
+		fmt.Fprintf(w, "%s (%s * %d [%s, %s])\n", elem.Total, elem.MeanTime(), elem.Count, elem.Min, elem.Max)
+		missinggo.WriteStack(w, elem.stack[:])
+	}
+}
+
+func Enable() {
+	EnableContention()
+	EnableLockTimes()
+}
+
+func EnableContention() {
+	lockHolders = pprof.NewProfile("lockHolders")
+	lockBlockers = pprof.NewProfile("lockBlockers")
+	noSharedLocking = true
+	contentionOn = true
+}
+
+func EnableLockTimes() {
+	lockStatsByStack = make(map[lockStackKey]lockStats)
+	http.DefaultServeMux.HandleFunc("/debug/lockTimes", func(w http.ResponseWriter, r *http.Request) {
+		PrintLockTimes(w)
+	})
+	noSharedLocking = true
+	lockTimesOn = true
+}
+
+func init() {
+	env := os.Getenv("PPROF_SYNC")
+	all := true
+	if strings.Contains(env, "times") {
+		EnableLockTimes()
+		all = false
+	}
+	if strings.Contains(env, "contention") {
+		EnableContention()
+		all = false
+	}
+	if all && env != "" {
+		Enable()
+	}
+}