From 7c8bd2322c7fd973d089b27de55e29c92c667a06 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 10 Dec 2014 15:45:33 -0800 Subject: [PATCH] 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 Cc: Aaron Tomlin Cc: Alexey Dobriyan Cc: "Eric W. Biederman" , Cc: Sterling Alexander Cc: Peter Zijlstra Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/ptrace.h | 2 +- kernel/exit.c | 10 ++++------ kernel/ptrace.c | 23 +++-------------------- 3 files changed, 8 insertions(+), 27 deletions(-) diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index cc79eff4a1ad..987a73a40ef8 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -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 diff --git a/kernel/exit.c b/kernel/exit.c index 772e9175735c..9c9526d87276 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -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; diff --git a/kernel/ptrace.c b/kernel/ptrace.c index 54e75226c2c4..1eb9d90c3af9 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -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) -- 2.20.1