Commit b564daf8 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

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: default avatarOleg Nesterov <oleg@tv-sign.ru>
Acked-by: default avatarRoland McGrath <roland@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9d5b327b

fs/exec.c

+2 −0
Original line number Diff line number Diff line
@@ -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);

include/linux/mm_types.h

+6 −0
Original line number Diff line number Diff line
@@ -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;

};

kernel/exit.c

+12 −3
Original line number Diff line number Diff line
@@ -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);

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