From 0e49214c7eb241d32162445ac5904c8a9d31822c Mon Sep 17 00:00:00 2001
From: Sergey Lyubka <valenok@gmail.com>
Date: Sun, 1 Dec 2013 09:46:05 +0000
Subject: [PATCH] Added mutex protection for write calls

---
 build/src/core.c | 49 ++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 43 insertions(+), 6 deletions(-)

diff --git a/build/src/core.c b/build/src/core.c
index 605f8b1a..28f3e259 100644
--- a/build/src/core.c
+++ b/build/src/core.c
@@ -59,10 +59,15 @@ typedef unsigned int  uint32_t;
 typedef unsigned short  uint16_t;
 typedef unsigned __int64 uint64_t;
 typedef __int64   int64_t;
+typedef CRITICAL_SECTION mutex_t;
 #pragma comment(lib, "ws2_32.lib")
 #define snprintf _snprintf
 #define vsnprintf _vsnprintf
 #define INT64_FMT  "I64d"
+#define mutex_init(x) InitializeCriticalSection(x)
+#define mutex_destroy(x) DeleteCriticalSection(x)
+#define mutex_lock(x) EnterCriticalSection(x)
+#define mutex_unlock(x) LeaveCriticalSection(x)
 #ifndef va_copy
 #define va_copy(x,y) x = y
 #endif // MINGW #defines va_copy
@@ -78,6 +83,11 @@ typedef __int64   int64_t;
 #include <sys/select.h>
 #define closesocket(x) close(x)
 typedef int sock_t;
+typedef pthread_mutex_t mutex_t;
+#define mutex_init(x) pthread_mutex_init(x, NULL)
+#define mutex_destroy(x) pthread_mutex_destroy(x)
+#define mutex_lock(x) pthread_mutex_lock(x)
+#define mutex_unlock(x) pthread_mutex_unlock(x)
 #define INVALID_SOCKET ((sock_t) -1)
 #define INT64_FMT PRId64
 #endif
@@ -102,9 +112,13 @@ struct linked_list_link { struct linked_list_link *prev, *next; };
 #define MAX_REQUEST_SIZE 16384
 #define IOBUF_SIZE 8192
 #define MAX_PATH_SIZE 8192
+
+#ifdef ENABLE_DBG
 #define DBG(x) do { printf("%s::%s() ", __FILE__, __func__); \
   printf x; putchar('\n'); fflush(stdout); } while(0)
-//#define DBG(x)
+#else
+#define DBG(x)
+#endif
 
 union socket_address {
   struct sockaddr sa;
@@ -156,7 +170,7 @@ enum connection_flags { CONN_CLOSE = 1, CONN_SPOOL_DONE = 2 };
 struct mg_connection {
   struct linked_list_link link;   // Linkage to server->active_connections
   struct mg_server *server;
-  struct mg_event event;
+  struct mg_event event;      // NOTE(lsm): this has conn_data attribute
   sock_t client_sock;         // Connected client
   union socket_address csa;   // Client's socket address
   struct iobuf local_iobuf;
@@ -168,6 +182,7 @@ struct mg_connection {
   struct mg_request_info request_info;
   char *path_info;
   int request_len;
+  mutex_t mutex;   // Guards concurrent mg_write() and mg_printf() calls
 };
 
 static const char *static_config_options[] = {
@@ -476,8 +491,11 @@ static struct mg_connection *accept_new_connection(struct mg_server *server) {
   struct mg_connection *conn = NULL;
 
   if ((sock = accept(server->listening_sock, &sa.sa, &len)) == INVALID_SOCKET) {
+#if 0
   } else if (sock >= FD_SETSIZE) {
+    DBG((">fd_setsize"));
     closesocket(sock);
+#endif
   } else if (!check_acl(server->config_options[ACCESS_CONTROL_LIST],
                         ntohl(* (uint32_t *) &sa.sin.sin_addr))) {
     closesocket(sock);
@@ -495,6 +513,7 @@ static struct mg_connection *accept_new_connection(struct mg_server *server) {
     conn->local_iobuf.size = MAX_REQUEST_SIZE;
     conn->remote_iobuf.buf = (char *) calloc(1, IOBUF_SIZE);
     conn->remote_iobuf.size = IOBUF_SIZE;
+    mutex_init(&conn->mutex);
     LINKED_LIST_ADD_TO_FRONT(&server->active_connections, &conn->link);
     DBG(("added conn %p", conn));
   }
@@ -507,6 +526,7 @@ static void close_conn(struct mg_connection *conn) {
   LINKED_LIST_REMOVE(&conn->link);
   closesocket(conn->client_sock);
   free(conn->remote_iobuf.buf);
+  mutex_destroy(&conn->mutex);
   free(conn);
 }
 
@@ -756,12 +776,12 @@ static int convert_uri_to_file_name(struct mg_connection *conn, char *buf,
 }
 
 static int spool(struct iobuf *io, const void *buf, int len) {
-  char *ptr = io->buf;
+  char *p = io->buf;
 
   if (len <= 0) {
   } else if (len < io->size - io->len ||
-             (ptr = realloc(io->buf, io->len + len - io->size)) != NULL) {
-    io->buf = ptr;
+             (p = (char *) realloc(io->buf, io->len + len - io->size)) != 0) {
+    io->buf = p;
     memcpy(io->buf + io->len, buf, len);
     io->len += len;
   } else {
@@ -796,13 +816,21 @@ int mg_printf(struct mg_connection *conn, const char *fmt, ...) {
   va_list ap;
   int ret;
   va_start(ap, fmt);
+  mutex_lock(&conn->mutex);
   ret = vspool(&conn->remote_iobuf, fmt, ap);
+  mutex_unlock(&conn->mutex);
   va_end(ap);
+  send(conn->server->ctl[1], ".", 1, 0);  // Wake up select call
   return ret;
 }
 
 int mg_write(struct mg_connection *conn, const void *buf, int len) {
-  return spool(&conn->remote_iobuf, buf, len);
+  int ret;
+  mutex_lock(&conn->mutex);
+  ret = spool(&conn->remote_iobuf, buf, len);
+  mutex_unlock(&conn->mutex);
+  send(conn->server->ctl[1], ".", 1, 0);  // Wake up select call
+  return ret;
 }
 
 static int is_error(int n) {
@@ -983,6 +1011,13 @@ void mg_poll_server(struct mg_server *server, unsigned int milliseconds) {
   tv.tv_usec = (milliseconds % 1000) * 1000;
 
   if (select(max_fd + 1, &read_set, &write_set, NULL, &tv) > 0) {
+    // If control socket is set, just read from it. It meant to wake up
+    // this select loop when another thread writes to any connection
+    if (FD_ISSET(server->ctl[0], &read_set)) {
+      char buf[500];
+      recv(server->ctl[0], buf, sizeof(buf), 0);
+    }
+
     // Accept new connections
     if (FD_ISSET(server->listening_sock, &read_set)) {
       while ((conn = accept_new_connection(server)) != NULL) {
@@ -1080,6 +1115,8 @@ struct mg_server *mg_create_server(const char *opts[], mg_event_handler_t func,
   return server;
 }
 
+// End of library, start of the application code
+
 static int event_handler(struct mg_event *ev) {
   mg_printf(ev->conn, "%s", "HTTP/1.0 200 OK\r\n\r\n:-)\n");
   return 1;