Commit 7c8bd232 authored by Oleg Nesterov's avatar Oleg Nesterov Committed by Linus Torvalds
Browse files

exit: ptrace: shift "reap dead" code from exit_ptrace() to forget_original_parent() 



Now that forget_original_parent() uses ->ptrace_entry for EXIT_DEAD tasks,
we can simply pass "dead_children" list to exit_ptrace() and remove
another release_task() loop.  Plus this way we do not need to drop and
reacquire tasklist_lock.

Also shift the list_empty(ptraced) check, if we want this optimization it
makes sense to eliminate the function call altogether.

Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: Aaron Tomlin <atomlin@redhat.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
Cc: Sterling Alexander <stalexan@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roland McGrath <roland@hack.frob.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2831096e

include/linux/ptrace.h

+1 −1
Original line number Diff line number Diff line
@@ -52,7 +52,7 @@ extern void ptrace_notify(int exit_code); 
extern void __ptrace_link(struct task_struct *child,

			  struct task_struct *new_parent);

extern void __ptrace_unlink(struct task_struct *child);

extern void exit_ptrace(struct task_struct *tracer);

extern void exit_ptrace(struct task_struct *tracer, struct list_head *dead);

#define PTRACE_MODE_READ	0x01

#define PTRACE_MODE_ATTACH	0x02

#define PTRACE_MODE_NOAUDIT	0x04

kernel/exit.c

+4 −6
Original line number Diff line number Diff line
@@ -553,13 +553,11 @@ static void forget_original_parent(struct task_struct *father) 
	LIST_HEAD(dead_children);



	write_lock_irq(&tasklist_lock);

	/*

	 * Note that exit_ptrace() and find_new_reaper() might

	 * drop tasklist_lock and reacquire it.

	 */

	exit_ptrace(father);

	reaper = find_new_reaper(father);

	if (unlikely(!list_empty(&father->ptraced)))

		exit_ptrace(father, &dead_children);



	/* Can drop and reacquire tasklist_lock */

	reaper = find_new_reaper(father);

	list_for_each_entry(p, &father->children, sibling) {

		for_each_thread(p, t) {

			t->real_parent = reaper;

kernel/ptrace.c

+3 −20
Original line number Diff line number Diff line
@@ -485,36 +485,19 @@ static int ptrace_detach(struct task_struct *child, unsigned int data) 


/*

 * Detach all tasks we were using ptrace on. Called with tasklist held

 * for writing, and returns with it held too. But note it can release

 * and reacquire the lock.

 * for writing.

 */

void exit_ptrace(struct task_struct *tracer)

	__releases(&tasklist_lock)

	__acquires(&tasklist_lock)

void exit_ptrace(struct task_struct *tracer, struct list_head *dead)

{

	struct task_struct *p, *n;

	LIST_HEAD(ptrace_dead);



	if (likely(list_empty(&tracer->ptraced)))

		return;



	list_for_each_entry_safe(p, n, &tracer->ptraced, ptrace_entry) {

		if (unlikely(p->ptrace & PT_EXITKILL))

			send_sig_info(SIGKILL, SEND_SIG_FORCED, p);



		if (__ptrace_detach(tracer, p))

			list_add(&p->ptrace_entry, &ptrace_dead);

	}



	write_unlock_irq(&tasklist_lock);

	BUG_ON(!list_empty(&tracer->ptraced));



	list_for_each_entry_safe(p, n, &ptrace_dead, ptrace_entry) {

		list_del_init(&p->ptrace_entry);

		release_task(p);

			list_add(&p->ptrace_entry, dead);

	}



	write_lock_irq(&tasklist_lock);

}



int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)

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