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coredump: construct the list of coredumping threads at startup time

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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>
This commit is contained in:
Oleg Nesterov 2008-07-25 01:47:44 -07:00 • committed by Linus Torvalds
parent 9d5b327bf1
commit b564daf806
3 changed files with 20 additions and 3 deletions
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2
fs/exec.c
View file

@ -1604,6 +1604,8 @@ static int coredump_wait(int exit_code, struct core_state *core_state)
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);

6
include/linux/mm_types.h
View file

@ -159,8 +159,14 @@ struct vm_area_struct {
#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;
};

15
kernel/exit.c
View file

@ -664,6 +664,7 @@ assign_new_owner:
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 @@ static void exit_mm(struct task_struct * tsk)
* 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);