add concurrent inserts test

3 files changed, 161 insertions, 7 deletions

diff --git a/all_test.go b/all_test.go
index cc0447c..0ec9844 100644
--- a/all_test.go
+++ b/all_test.go
@@ -6,6 +6,7 @@ package sqlite // import "modernc.org/sqlite"
 
 import (
 	"bytes"
+	"context"
 	"database/sql"
 	"flag"
 	"fmt"
@@ -15,8 +16,11 @@ import (
 	"path/filepath"
 	"runtime"
 	"strings"
+	"sync"
 	"testing"
 	"time"
+
+	"modernc.org/mathutil"
 )
 
 func caller(s string, va ...interface{}) {
@@ -348,3 +352,107 @@ func TestMemDB(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestConcurrentInserts(t *testing.T) {
+	const (
+		ngoroutines = 8
+		nrows       = 2500
+	)
+
+	dir, err := ioutil.TempDir("", "sqlite-test-")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	defer os.RemoveAll(dir)
+
+	db, err := sql.Open(driverName, filepath.Join(dir, "test.db"))
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tx, err := db.BeginTx(context.Background(), nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if _, err := tx.Exec("create table t(i)"); err != nil {
+		t.Fatal(err)
+	}
+
+	prep, err := tx.Prepare("insert into t values(?)")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rnd := make(chan int, 100)
+	go func() {
+		lim := ngoroutines * nrows
+		rng, err := mathutil.NewFC32(0, lim-1, false)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		for i := 0; i < lim; i++ {
+			rnd <- int(rng.Next())
+		}
+	}()
+
+	start := make(chan int)
+	var wg sync.WaitGroup
+	for i := 0; i < ngoroutines; i++ {
+		wg.Add(1)
+
+		go func(id int) {
+
+			defer wg.Done()
+
+		next:
+			for i := 0; i < nrows; i++ {
+				n := <-rnd
+				var err error
+				for j := 0; j < 10; j++ {
+					if _, err := prep.Exec(n); err == nil {
+						continue next
+					}
+				}
+
+				t.Errorf("id %d, seq %d: %v", id, i, err)
+				return
+			}
+		}(i)
+	}
+	t0 := time.Now()
+	close(start)
+	wg.Wait()
+	if err := tx.Commit(); err != nil {
+		t.Fatal(err)
+	}
+
+	d := time.Since(t0)
+	rows, err := db.Query("select * from t order by i")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var i int
+	for ; rows.Next(); i++ {
+		var j int
+		if err := rows.Scan(&j); err != nil {
+			t.Fatalf("seq %d: %v", i, err)
+		}
+
+		if g, e := j, i; g != e {
+			t.Fatalf("seq %d: got %d, exp %d", i, g, e)
+		}
+	}
+	if err := rows.Err(); err != nil {
+		t.Fatal(err)
+	}
+
+	if g, e := i, ngoroutines*nrows; g != e {
+		t.Fatalf("got %d rows, expected %d", g, e)
+	}
+
+	t.Logf("%d goroutines concurrently inserted %d rows in %v", ngoroutines, ngoroutines*nrows, d)
+}
diff --git a/go.mod b/go.mod
index 1685ff1..5895e86 100644
--- a/go.mod
+++ b/go.mod
@@ -2,4 +2,7 @@ module modernc.org/sqlite
 
 go 1.13
 
-require modernc.org/crt/v2 v2.0.0-20191219143825-5728f219e36a
+require (
+	modernc.org/crt/v2 v2.0.0-20191219143825-5728f219e36a
+	modernc.org/mathutil v1.0.0
+)
diff --git a/mutex.go b/mutex.go
index 0bcc241..5b5cc15 100644
--- a/mutex.go
+++ b/mutex.go
@@ -52,10 +52,17 @@ type mutex struct {
 	cnt int32
 	id  int32
 	sync.Mutex
-	wait sync.Mutex
+	wait      sync.Mutex
+	recursive bool
 }
 
 func (m *mutex) enter(id int32) {
+	if !m.recursive {
+		m.Lock()
+		m.id = id
+		return
+	}
+
 	for {
 		m.Lock()
 		switch m.id {
@@ -77,7 +84,36 @@ func (m *mutex) enter(id int32) {
 	}
 }
 
+func (m *mutex) try(id int32) int32 {
+	if !m.recursive {
+		return bin.DSQLITE_BUSY
+	}
+
+	m.Lock()
+	switch m.id {
+	case 0:
+		m.cnt = 1
+		m.id = id
+		m.wait.Lock()
+		m.Unlock()
+		return bin.DSQLITE_OK
+	case id:
+		m.cnt++
+		m.Unlock()
+		return bin.DSQLITE_OK
+	}
+
+	m.Unlock()
+	return bin.DSQLITE_BUSY
+}
+
 func (m *mutex) leave() {
+	if !m.recursive {
+		m.id = 0
+		m.Unlock()
+		return
+	}
+
 	m.Lock()
 	m.cnt--
 	if m.cnt == 0 {
@@ -155,11 +191,12 @@ func mutexAlloc(tls *crt.TLS, typ int32) (r crt.Intptr) {
 	defer func() {
 	}()
 	switch typ {
-	case
-		bin.DSQLITE_MUTEX_FAST,
-		bin.DSQLITE_MUTEX_RECURSIVE:
-
+	case bin.DSQLITE_MUTEX_FAST:
 		return crt.Xcalloc(tls, 1, crt.Intptr(unsafe.Sizeof(mutex{})))
+	case bin.DSQLITE_MUTEX_RECURSIVE:
+		p := crt.Xcalloc(tls, 1, crt.Intptr(unsafe.Sizeof(mutex{})))
+		(*mutex)(unsafe.Pointer(uintptr(p))).recursive = true
+		return p
 	case bin.DSQLITE_MUTEX_STATIC_MASTER:
 		return crt.Intptr(uintptr(unsafe.Pointer(&mutexMaster)))
 	case bin.DSQLITE_MUTEX_STATIC_MEM:
@@ -216,7 +253,13 @@ func mutexEnter(tls *crt.TLS, m crt.Intptr) {
 }
 
 // int (*xMutexTry)(sqlite3_mutex *);
-func mutexTry(tls *crt.TLS, m crt.Intptr) int32 { return bin.DSQLITE_BUSY }
+func mutexTry(tls *crt.TLS, m crt.Intptr) int32 {
+	if m == 0 {
+		return bin.DSQLITE_OK
+	}
+
+	return (*mutex)(unsafe.Pointer(uintptr(m))).try(tls.ID)
+}
 
 // void (*xMutexLeave)(sqlite3_mutex *);
 func mutexLeave(tls *crt.TLS, m crt.Intptr) {