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Commit 999d9fc1 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
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coredump: move mm->core_waiters into struct core_state 



Move mm->core_waiters into "struct core_state" allocated on stack.  This
shrinks mm_struct a little bit and allows further changes.

This patch mostly does s/core_waiters/core_state.  The only essential
change is that coredump_wait() must clear mm->core_state before return.

The coredump_wait()'s path is uglified and .text grows by 30 bytes, this
is fixed by the next patch.

Signed-off-by: default avatarOleg Nesterov <oleg@tv-sign.ru>
Cc: Roland 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 32ecb1f2

fs/exec.c

+11 −10
Original line number Diff line number Diff line
@@ -722,12 +722,10 @@ static int exec_mmap(struct mm_struct *mm) 
		 * Make sure that if there is a core dump in progress

		 * for the old mm, we get out and die instead of going

		 * through with the exec.  We must hold mmap_sem around

		 * checking core_waiters and changing tsk->mm.  The

		 * core-inducing thread will increment core_waiters for

		 * each thread whose ->mm == old_mm.

		 * checking core_state and changing tsk->mm.

		 */

		down_read(&old_mm->mmap_sem);

		if (unlikely(old_mm->core_waiters)) {

		if (unlikely(old_mm->core_state)) {

			up_read(&old_mm->mmap_sem);

			return -EINTR;

		}
@@ -1514,7 +1512,7 @@ static void zap_process(struct task_struct *start) 
	t = start;

	do {

		if (t != current && t->mm) {

			t->mm->core_waiters++;

			t->mm->core_state->nr_threads++;

			sigaddset(&t->pending.signal, SIGKILL);

			signal_wake_up(t, 1);

		}
@@ -1538,11 +1536,11 @@ static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm, 
	if (err)

		return err;



	if (atomic_read(&mm->mm_users) == mm->core_waiters + 1)

	if (atomic_read(&mm->mm_users) == mm->core_state->nr_threads + 1)

		goto done;

	/*

	 * We should find and kill all tasks which use this mm, and we should

	 * count them correctly into mm->core_waiters. We don't take tasklist

	 * count them correctly into ->nr_threads. We don't take tasklist

	 * lock, but this is safe wrt:

	 *

	 * fork:
@@ -1590,7 +1588,7 @@ static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm, 
	}

	rcu_read_unlock();

done:

	return mm->core_waiters;

	return mm->core_state->nr_threads;

}



static int coredump_wait(int exit_code)
@@ -1603,9 +1601,12 @@ static int coredump_wait(int exit_code) 


	init_completion(&mm->core_done);

	init_completion(&core_state.startup);

	core_state.nr_threads = 0;

	mm->core_state = &core_state;



	core_waiters = zap_threads(tsk, mm, exit_code);

	if (core_waiters < 0)

		mm->core_state = NULL;

	up_write(&mm->mmap_sem);



	if (unlikely(core_waiters < 0))
@@ -1623,8 +1624,8 @@ static int coredump_wait(int exit_code) 


	if (core_waiters)

		wait_for_completion(&core_state.startup);

	mm->core_state = NULL;

fail:

	BUG_ON(mm->core_waiters);

	return core_waiters;

}
@@ -1702,7 +1703,7 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs) 
	/*

	 * If another thread got here first, or we are not dumpable, bail out.

	 */

	if (mm->core_waiters || !get_dumpable(mm)) {

	if (mm->core_state || !get_dumpable(mm)) {

		up_write(&mm->mmap_sem);

		goto fail;

	}

include/linux/mm_types.h

+1 −1
Original line number Diff line number Diff line
@@ -160,6 +160,7 @@ struct vm_area_struct { 
};



struct core_state {

	int nr_threads;

	struct completion startup;

};
@@ -179,7 +180,6 @@ struct mm_struct { 
	atomic_t mm_users;			/* How many users with user space? */

	atomic_t mm_count;			/* How many references to "struct mm_struct" (users count as 1) */

	int map_count;				/* number of VMAs */

	int core_waiters;

	struct rw_semaphore mmap_sem;

	spinlock_t page_table_lock;		/* Protects page tables and some counters */

kernel/exit.c

+4 −4
Original line number Diff line number Diff line
@@ -670,16 +670,16 @@ static void exit_mm(struct task_struct * tsk) 
		return;

	/*

	 * Serialize with any possible pending coredump.

	 * We must hold mmap_sem around checking core_waiters

	 * We must hold mmap_sem around checking core_state

	 * and clearing tsk->mm.  The core-inducing thread

	 * will increment core_waiters for each thread in the

	 * will increment ->nr_threads for each thread in the

	 * group with ->mm != NULL.

	 */

	down_read(&mm->mmap_sem);

	if (mm->core_waiters) {

	if (mm->core_state) {

		up_read(&mm->mmap_sem);

		down_write(&mm->mmap_sem);

		if (!--mm->core_waiters)

		if (!--mm->core_state->nr_threads)

			complete(&mm->core_state->startup);

		up_write(&mm->mmap_sem);

kernel/fork.c

+1 −1
Original line number Diff line number Diff line
@@ -400,7 +400,7 @@ static struct mm_struct * mm_init(struct mm_struct * mm, struct task_struct *p) 
	INIT_LIST_HEAD(&mm->mmlist);

	mm->flags = (current->mm) ? current->mm->flags

				  : MMF_DUMP_FILTER_DEFAULT;

	mm->core_waiters = 0;

	mm->core_state = NULL;

	mm->nr_ptes = 0;

	set_mm_counter(mm, file_rss, 0);

	set_mm_counter(mm, anon_rss, 0);

kernel/signal.c

+2 −2
Original line number Diff line number Diff line
@@ -1480,10 +1480,10 @@ static inline int may_ptrace_stop(void) 
	 * is a deadlock situation, and pointless because our tracer

	 * is dead so don't allow us to stop.

	 * If SIGKILL was already sent before the caller unlocked

	 * ->siglock we must see ->core_waiters != 0. Otherwise it

	 * ->siglock we must see ->core_state != NULL. Otherwise it

	 * is safe to enter schedule().

	 */

	if (unlikely(current->mm->core_waiters) &&

	if (unlikely(current->mm->core_state) &&

	    unlikely(current->mm == current->parent->mm))

		return 0;