http://sourceware.org/ml/gdb-patches/2010-09/msg00361.html
Subject: [patch 4/4]#3 Remove redundant lp->siginfo

Hi,

this is a simplification which should not affect GDB behavior.  As linux-nat
now stops on each received signal without any reordering of them then
PTRACE_GETSIGINFO is enough to access siginfo, without any need to copy it in
advance.


Thanks,
Jan


gdb/
2010-09-20  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* linux-nat.c (resume_callback) <lp->stopped && lp->status == 0>
	(linux_nat_resume): Remove LP->SIGINFO clearing.
	(save_siginfo): Remove.
	(stop_wait_callback) <WSTOPSIG (status) != SIGSTOP>
	(linux_nat_filter_event) <linux_nat_status_is_event (status)>: Remove
	the save_siginfo call.
	(resume_stopped_resumed_lwps): Remove LP->SIGINFO clearing.
	(linux_nat_set_siginfo_fixup): Use PTRACE_GETSIGINFO.
	* linux-nat.h (struct lwp_info) <siginfo>: Remove.

Index: gdb-7.4.50.20120703/gdb/linux-nat.c
===================================================================
--- gdb-7.4.50.20120703.orig/gdb/linux-nat.c	2012-07-03 17:33:02.000000000 +0200
+++ gdb-7.4.50.20120703/gdb/linux-nat.c	2012-07-03 17:38:36.738142509 +0200
@@ -1933,7 +1933,6 @@ resume_lwp (struct lwp_info *lp, int ste
 				step, signo);
 	  lp->stopped = 0;
 	  lp->step = step;
-	  memset (&lp->siginfo, 0, sizeof (lp->siginfo));
 	  lp->stopped_by_watchpoint = 0;
 	}
       else
@@ -2092,7 +2091,6 @@ linux_nat_resume (struct target_ops *ops
   if (linux_nat_prepare_to_resume != NULL)
     linux_nat_prepare_to_resume (lp);
   linux_ops->to_resume (linux_ops, ptid, step, signo);
-  memset (&lp->siginfo, 0, sizeof (lp->siginfo));
   lp->stopped_by_watchpoint = 0;
 
   if (debug_linux_nat)
@@ -2646,22 +2644,6 @@ wait_lwp (struct lwp_info *lp)
   return status;
 }
 
-/* Save the most recent siginfo for LP.  This is currently only called
-   for SIGTRAP; some ports use the si_addr field for
-   target_stopped_data_address.  In the future, it may also be used to
-   restore the siginfo of requeued signals.  */
-
-static void
-save_siginfo (struct lwp_info *lp)
-{
-  errno = 0;
-  ptrace (PTRACE_GETSIGINFO, GET_LWP (lp->ptid),
-	  (PTRACE_TYPE_ARG3) 0, &lp->siginfo);
-
-  if (errno != 0)
-    memset (&lp->siginfo, 0, sizeof (lp->siginfo));
-}
-
 /* Send a SIGSTOP to LP.  */
 
 static int
@@ -2904,9 +2886,6 @@ stop_wait_callback (struct lwp_info *lp,
 	{
 	  /* The thread was stopped with a signal other than SIGSTOP.  */
 
-	  /* Save the trap's siginfo in case we need it later.  */
-	  save_siginfo (lp);
-
 	  save_sigtrap (lp);
 
 	  if (debug_linux_nat)
@@ -3288,12 +3267,7 @@ linux_nat_filter_event (int lwpid, int s
     }
 
   if (linux_nat_status_is_event (status))
-    {
-      /* Save the trap's siginfo in case we need it later.  */
-      save_siginfo (lp);
-
-      save_sigtrap (lp);
-    }
+    save_sigtrap (lp);
 
   /* Check if the thread has exited.  */
   if ((WIFEXITED (status) || WIFSIGNALED (status))
@@ -3947,7 +3921,6 @@ resume_stopped_resumed_lwps (struct lwp_
       linux_ops->to_resume (linux_ops, pid_to_ptid (GET_LWP (lp->ptid)),
 			    lp->step, GDB_SIGNAL_0);
       lp->stopped = 0;
-      memset (&lp->siginfo, 0, sizeof (lp->siginfo));
       lp->stopped_by_watchpoint = 0;
     }
 
@@ -5224,11 +5197,19 @@ linux_nat_set_prepare_to_resume (struct
 siginfo_t *
 linux_nat_get_siginfo (ptid_t ptid)
 {
-  struct lwp_info *lp = find_lwp_pid (ptid);
+  static siginfo_t siginfo;
+  int pid;
 
-  gdb_assert (lp != NULL);
+  pid = GET_LWP (ptid);
+  if (pid == 0)
+    pid = GET_PID (ptid);
+
+  errno = 0;
+  ptrace (PTRACE_GETSIGINFO, pid, (PTRACE_TYPE_ARG3) 0, &siginfo);
+  if (errno != 0)
+    memset (&siginfo, 0, sizeof (siginfo));
 
-  return &lp->siginfo;
+  return &siginfo;
 }
 
 /* Provide a prototype to silence -Wmissing-prototypes.  */
Index: gdb-7.4.50.20120703/gdb/linux-nat.h
===================================================================
--- gdb-7.4.50.20120703.orig/gdb/linux-nat.h	2012-07-03 17:30:09.000000000 +0200
+++ gdb-7.4.50.20120703/gdb/linux-nat.h	2012-07-03 17:38:13.501170247 +0200
@@ -76,10 +76,6 @@ struct lwp_info
   /* The kind of stepping of this LWP.  */
   enum resume_step step;
 
-  /* Non-zero si_signo if this LWP stopped with a trap.  si_addr may
-     be the address of a hardware watchpoint.  */
-  siginfo_t siginfo;
-
   /* STOPPED_BY_WATCHPOINT is non-zero if this LWP stopped with a data
      watchpoint trap.  */
   int stopped_by_watchpoint;