Fix adb hang when subprocess dies early.

* Handling of the subprocess and its FD.
  This fixes http://b/3400254 "Many bugreports getting hung at the end in monkey"
  -  Start up a service thread that waits on the subprocess to terminate,
then closes the FD associated with it.
  -  Have the event handler select() with a timeout so that it can
  detect the closed FD. Select() with no timeout does not return when an FD is closed.
  - Have the event handler force a read on the closed FD to trigger the close sequence.
  - Migrate the "shell:blabla" handling to "#if !ADB_HOST" sections.
* Fix the race around OOM adjusting.
  - Do it in the child before exec() instead of the in the parent as the
   child could already have started or not (no /proc/pid/... yet).
* Allow for multi-threaded D() invocations to not clobber each other.
  - Allow locks across object files.
  - Add lock within D()
* Add some missing close(fd) calls
  - Match similar existing practices near dup2()
* Add extra D() invocations related to FD handling.
* Warn about using debugging as stderr/stdout is used for protocol.

Change-Id: Ie5c4a5e6bfbe3f22201adf5f9a205d32e069bf9d
Signed-off-by: JP Abgrall <jpa@google.com>
diff --git a/adb/transport.c b/adb/transport.c
index 2baf340..2d678b2 100644
--- a/adb/transport.c
+++ b/adb/transport.c
@@ -35,24 +35,30 @@
 ADB_MUTEX_DEFINE( transport_lock );
 
 #if ADB_TRACE
+#define MAX_DUMP_HEX_LEN 16
 static void  dump_hex( const unsigned char*  ptr, size_t  len )
 {
     int  nn, len2 = len;
+    // Build a string instead of logging each character.
+    // MAX chars in 2 digit hex, one space, MAX chars, one '\0'.
+    char buffer[MAX_DUMP_HEX_LEN *2 + 1 + MAX_DUMP_HEX_LEN + 1 ], *pb = buffer;
 
-    if (len2 > 16) len2 = 16;
+    if (len2 > MAX_DUMP_HEX_LEN) len2 = MAX_DUMP_HEX_LEN;
 
-    for (nn = 0; nn < len2; nn++)
-        D("%02x", ptr[nn]);
-    D("  ");
+    for (nn = 0; nn < len2; nn++) {
+        sprintf(pb, "%02x", ptr[nn]);
+        pb += 2;
+    }
+    sprintf(pb++, " ");
 
     for (nn = 0; nn < len2; nn++) {
         int  c = ptr[nn];
         if (c < 32 || c > 127)
             c = '.';
-        D("%c", c);
+        *pb++ =  c;
     }
-    D("\n");
-    fflush(stdout);
+    *pb++ = '\0';
+    DR("%s\n", buffer);
 }
 #endif
 
@@ -192,6 +198,7 @@
 static void transport_socket_events(int fd, unsigned events, void *_t)
 {
     atransport *t = _t;
+    D("transport_socket_events(fd=%d, events=%04x,...)\n", fd, events);
     if(events & FDE_READ){
         apacket *p = 0;
         if(read_packet(fd, t->serial, &p)){
@@ -221,8 +228,8 @@
     print_packet("send", p);
 
     if (t == NULL) {
-        fatal_errno("Transport is null");
         D("Transport is null \n");
+        fatal_errno("Transport is null");
     }
 
     if(write_packet(t->transport_socket, t->serial, &p)){
@@ -1069,4 +1076,3 @@
         return 0;
     }
 }
-