coredump: construct the list of coredumping threads at startup time
binfmt->core_dump() has to iterate over the all threads in system in order
to find the coredumping threads and construct the list using the
GFP_ATOMIC allocations.
With this patch each thread allocates the list node on exit_mm()'s stack and
adds itself to the list.
This allows us to do further changes:
- simplify ->core_dump()
- change exit_mm() to clear ->mm first, then wait for ->core_done.
this makes the coredumping process visible to oom_kill
- kill mm->core_done
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>
diff --git a/fs/exec.c b/fs/exec.c
index b8ee842..fe2873b 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1604,6 +1604,8 @@
init_completion(&mm->core_done);
init_completion(&core_state->startup);
+ core_state->dumper.task = tsk;
+ core_state->dumper.next = NULL;
core_waiters = zap_threads(tsk, mm, core_state, exit_code);
up_write(&mm->mmap_sem);
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index ae99a28..4d0d0ab 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -159,8 +159,14 @@
#endif
};
+struct core_thread {
+ struct task_struct *task;
+ struct core_thread *next;
+};
+
struct core_state {
atomic_t nr_threads;
+ struct core_thread dumper;
struct completion startup;
};
diff --git a/kernel/exit.c b/kernel/exit.c
index 63d8295..b66f0d5 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -664,6 +664,7 @@
static void exit_mm(struct task_struct * tsk)
{
struct mm_struct *mm = tsk->mm;
+ struct core_state *core_state;
mm_release(tsk, mm);
if (!mm)
@@ -676,11 +677,19 @@
* group with ->mm != NULL.
*/
down_read(&mm->mmap_sem);
- if (mm->core_state) {
+ core_state = mm->core_state;
+ if (core_state) {
+ struct core_thread self;
up_read(&mm->mmap_sem);
- if (atomic_dec_and_test(&mm->core_state->nr_threads))
- complete(&mm->core_state->startup);
+ self.task = tsk;
+ self.next = xchg(&core_state->dumper.next, &self);
+ /*
+ * Implies mb(), the result of xchg() must be visible
+ * to core_state->dumper.
+ */
+ if (atomic_dec_and_test(&core_state->nr_threads))
+ complete(&core_state->startup);
wait_for_completion(&mm->core_done);
down_read(&mm->mmap_sem);
