[linux] Always ignore restart/cancellation signals

[Daniel Jacobowitz <drow@false.org>]

The comment is fairly self-explanatory.  I guess I've always debugged
failing cancellation tests with gdbserver, which hardwires these values
already...

Any objections?

-- 
Daniel Jacobowitz
CodeSourcery, LLC

2005-12-07  Daniel Jacobowitz  <dan@codesourcery.com>

	* linux-nat.c (lin_thread_get_thread_signals): Default to __SIGRTMIN
	and __SIGRTMIN + 1.

Index: gdb-6.4/gdb/linux-nat.c
===================================================================
--- gdb-6.4.orig/gdb/linux-nat.c	2005-11-03 14:51:40.000000000 -0500
+++ gdb-6.4/gdb/linux-nat.c	2005-12-07 21:44:12.000000000 -0500
@@ -3284,12 +3284,18 @@ lin_thread_get_thread_signals (sigset_t 
   sigemptyset (set);
 
   restart = get_signo ("__pthread_sig_restart");
+  cancel = get_signo ("__pthread_sig_cancel");
+
+  /* LinuxThreads normally uses the first two RT signals, but in some legacy
+     cases may use SIGUSR1/SIGUSR2.  NPTL always uses RT signals, but does
+     not provide any way for the debugger to query the signal numbers -
+     fortunately they don't change!  */
+
   if (restart == 0)
-    return;
+    restart = __SIGRTMIN;
 
-  cancel = get_signo ("__pthread_sig_cancel");
   if (cancel == 0)
-    return;
+    cancel = __SIGRTMIN + 1;
 
   sigaddset (set, restart);
   sigaddset (set, cancel);