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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: Oleg 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Oleg Nesterov 2014-12-10 15:45:33 -08:00 committed by Linus Torvalds
parent 2831096e21
commit 7c8bd2322c
3 changed files with 8 additions and 27 deletions
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2
include/linux/ptrace.h
View File

@ -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

10
kernel/exit.c
View File

@ -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;

23
kernel/ptrace.c
View File

@ -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);
list_add(&p->ptrace_entry, 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);
}
write_lock_irq(&tasklist_lock);
}
int ptrace_readdata(struct task_struct *tsk, unsigned long src, char __user *dst, int len)