From 901b98215e767bbffb1bfa869e02d7dc5ea786ec Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@polymtl.ca>
Date: Sat, 28 Aug 2021 10:58:45 -0400
Subject: gdb: use intrusive_list for linux-nat lwp_list

Replace the manually maintained linked list of lwp_info objects with
intrusive_list.  Replace the ALL_LWPS macro with all_lwps, which returns
a range.  Add all_lwps_safe as well, for use in iterate_over_lwps, which
currently iterates in a safe manner.

Change-Id: I355313502510acc0103f5eaf2fbde80897d6376c
---
 gdb/linux-nat.c | 46 ++++++++++++++++++++++++----------------------
 1 file changed, 24 insertions(+), 22 deletions(-)

(limited to 'gdb/linux-nat.c')

diff --git a/gdb/linux-nat.c b/gdb/linux-nat.c
index a297d3b..bac383d 100644
--- a/gdb/linux-nat.c
+++ b/gdb/linux-nat.c
@@ -421,9 +421,8 @@ static int
 num_lwps (int pid)
 {
   int count = 0;
-  struct lwp_info *lp;
 
-  for (lp = lwp_list; lp; lp = lp->next)
+  for (const lwp_info *lp ATTRIBUTE_UNUSED : all_lwps ())
     if (lp->ptid.pid () == pid)
       count++;
 
@@ -700,17 +699,31 @@ lwp_lwpid_htab_add_lwp (struct lwp_info *lp)
    creation order.  This order is assumed in some cases.  E.g.,
    reaping status after killing alls lwps of a process: the leader LWP
    must be reaped last.  */
-struct lwp_info *lwp_list;
+
+static intrusive_list<lwp_info> lwp_list;
+
+/* See linux-nat.h.  */
+
+lwp_info_range
+all_lwps ()
+{
+  return lwp_info_range (lwp_list.begin ());
+}
+
+/* See linux-nat.h.  */
+
+lwp_info_safe_range
+all_lwps_safe ()
+{
+  return lwp_info_safe_range (lwp_list.begin ());
+}
 
 /* Add LP to sorted-by-reverse-creation-order doubly-linked list.  */
 
 static void
 lwp_list_add (struct lwp_info *lp)
 {
-  lp->next = lwp_list;
-  if (lwp_list != NULL)
-    lwp_list->prev = lp;
-  lwp_list = lp;
+  lwp_list.push_front (*lp);
 }
 
 /* Remove LP from sorted-by-reverse-creation-order doubly-linked
@@ -720,12 +733,7 @@ static void
 lwp_list_remove (struct lwp_info *lp)
 {
   /* Remove from sorted-by-creation-order list.  */
-  if (lp->next != NULL)
-    lp->next->prev = lp->prev;
-  if (lp->prev != NULL)
-    lp->prev->next = lp->next;
-  if (lp == lwp_list)
-    lwp_list = lp->next;
+  lwp_list.erase (lwp_list.iterator_to (*lp));
 }
 
 
@@ -922,12 +930,8 @@ struct lwp_info *
 iterate_over_lwps (ptid_t filter,
 		   gdb::function_view<iterate_over_lwps_ftype> callback)
 {
-  struct lwp_info *lp, *lpnext;
-
-  for (lp = lwp_list; lp; lp = lpnext)
+  for (lwp_info *lp : all_lwps_safe ())
     {
-      lpnext = lp->next;
-
       if (lp->ptid.matches (filter))
 	{
 	  if (callback (lp) != 0)
@@ -3715,8 +3719,6 @@ linux_nat_target::thread_alive (ptid_t ptid)
 void
 linux_nat_target::update_thread_list ()
 {
-  struct lwp_info *lwp;
-
   /* We add/delete threads from the list as clone/exit events are
      processed, so just try deleting exited threads still in the
      thread list.  */
@@ -3724,7 +3726,7 @@ linux_nat_target::update_thread_list ()
 
   /* Update the processor core that each lwp/thread was last seen
      running on.  */
-  ALL_LWPS (lwp)
+  for (lwp_info *lwp : all_lwps ())
     {
       /* Avoid accessing /proc if the thread hasn't run since we last
 	 time we fetched the thread's core.  Accessing /proc becomes
@@ -3948,7 +3950,7 @@ linux_proc_xfer_memory_partial (gdb_byte *readbuf, const gdb_byte *writebuf,
 
   /* Iterate over LWPs of the current inferior, trying to access
      memory through one of them.  */
-  for (lwp_info *lp = lwp_list; lp != nullptr; lp = lp->next)
+  for (lwp_info *lp : all_lwps ())
     {
       if (lp->ptid.pid () != cur_pid)
 	continue;
-- 
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