coredump: elf_core_dump: use core_state->dumper list

Kill the nasty rcu_read_lock() + do_each_thread() loop, use the list
encoded in mm->core_state instead, s/GFP_ATOMIC/GFP_KERNEL/.

This patch allows futher cleanups in binfmt_elf.c, in particular we can
kill the parallel info->threads list.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 32 insertions, 45 deletions

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index bad7d8770d72..88d180306cf9 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -1478,7 +1478,7 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
         const struct user_regset_view *view = task_user_regset_view(dump_task);
         struct elf_thread_core_info *t;
         struct elf_prpsinfo *psinfo;
-        struct task_struct *g, *p;
+        struct core_thread *ct;
         unsigned int i;
 
         info->size = 0;
@@ -1517,34 +1517,26 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
         /*
          * Allocate a structure for each thread.
          */
-        rcu_read_lock();
-        do_each_thread(g, p)
-                if (p->mm == dump_task->mm) {
-                        if (p->flags & PF_KTHREAD)
-                                continue;
-
-                        t = kzalloc(offsetof(struct elf_thread_core_info,
-                                             notes[info->thread_notes]),
-                                    GFP_ATOMIC);
-                        if (unlikely(!t)) {
-                                rcu_read_unlock();
-                                return 0;
-                        }
-                        t->task = p;
-                        if (p == dump_task || !info->thread) {
-                                t->next = info->thread;
-                                info->thread = t;
-                        } else {
-                                /*
-                                 * Make sure to keep the original task at
-                                 * the head of the list.
-                                 */
-                                t->next = info->thread->next;
-                                info->thread->next = t;
-                        }
+        for (ct = &dump_task->mm->core_state->dumper; ct; ct = ct->next) {
+                t = kzalloc(offsetof(struct elf_thread_core_info,
+                                     notes[info->thread_notes]),
+                            GFP_KERNEL);
+                if (unlikely(!t))
+                        return 0;
+
+                t->task = ct->task;
+                if (ct->task == dump_task || !info->thread) {
+                        t->next = info->thread;
+                        info->thread = t;
+                } else {
+                        /*
+                         * Make sure to keep the original task at
+                         * the head of the list.
+                         */
+                        t->next = info->thread->next;
+                        info->thread->next = t;
                 }
-        while_each_thread(g, p);
-        rcu_read_unlock();
+        }
 
         /*
          * Now fill in each thread's information.
@@ -1691,7 +1683,6 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
 {
 #define NUM_NOTES       6
         struct list_head *t;
-        struct task_struct *g, *p;
 
         info->notes = NULL;
         info->prstatus = NULL;
@@ -1723,23 +1714,19 @@ static int fill_note_info(struct elfhdr *elf, int phdrs,
 
         info->thread_status_size = 0;
         if (signr) {
+                struct core_thread *ct;
                 struct elf_thread_status *ets;
-                rcu_read_lock();
-                do_each_thread(g, p)
-                        if (current->mm == p->mm && current != p) {
-                                if (p->flags & PF_KTHREAD)
-                                        continue;
-
-                                ets = kzalloc(sizeof(*ets), GFP_ATOMIC);
-                                if (!ets) {
-                                        rcu_read_unlock();
-                                        return 0;
-                                }
-                                ets->thread = p;
-                                list_add(&ets->list, &info->thread_list);
-                        }
-                while_each_thread(g, p);
-                rcu_read_unlock();
+
+                for (ct = current->mm->core_state->dumper.next;
+                                                ct; ct = ct->next) {
+                        ets = kzalloc(sizeof(*ets), GFP_KERNEL);
+                        if (!ets)
+                                return 0;
+
+                        ets->thread = ct->task;
+                        list_add(&ets->list, &info->thread_list);
+                }
+
                 list_for_each(t, &info->thread_list) {
                         int sz;