commit b04acb2651e0aaf615de50e9138cddfd5c24021f

Author: Andreas Schwab <schwab@suse.de>

Date:   Tue Jul 30 11:58:45 2013 +0200

    Fix race conditions in pldd that may leave the process stopped after detaching

    Fixes bug 15804

diff --git a/elf/pldd.c b/elf/pldd.c

index 684aff4..75f7812 100644

--- a/elf/pldd.c

+++ b/elf/pldd.c

@@ -34,6 +34,7 @@

 #include <unistd.h>

 #include <sys/ptrace.h>

 #include <sys/stat.h>

+#include <sys/wait.h>

 #include <ldsodefs.h>

 #include <version.h>

@@ -82,6 +83,7 @@ static char *exe;

 /* Local functions.  */

 static int get_process_info (int dfd, long int pid);

+static void wait_for_ptrace_stop (long int pid);

 int

@@ -170,6 +172,8 @@ main (int argc, char *argv[])

 		 tid);

 	}

+      wait_for_ptrace_stop (tid);

+

       struct thread_list *newp = alloca (sizeof (*newp));

       newp->tid = tid;

       newp->next = thread_list;

@@ -194,6 +198,27 @@ main (int argc, char *argv[])

 }

+/* Wait for PID to enter ptrace-stop state after being attached.  */

+static void

+wait_for_ptrace_stop (long int pid)

+{

+  int status;

+

+  /* While waiting for SIGSTOP being delivered to the tracee we have to

+     reinject any other pending signal.  Ignore all other errors.  */

+  while (waitpid (pid, &status, __WALL) == pid && WIFSTOPPED (status))

+    {

+      /* The STOP signal should not be delivered to the tracee.  */

+      if (WSTOPSIG (status) == SIGSTOP)

+	return;

+      if (ptrace (PTRACE_CONT, pid, NULL,

+		  (void *) (uintptr_t) WSTOPSIG (status)))

+	/* The only possible error is that the process died.  */

+	return;

+    }

+}

+

+

 /* Handle program arguments.  */

 static error_t

 parse_opt (int key, char *arg, struct argp_state *state)