From: Andy Lutomirski <luto@kernel.org> To: x86@kernel.org Cc: Borislav Petkov <bp@alien8.de>, linux-kernel@vger.kernel.org, Brian Gerst <brgerst@gmail.com>, Jann Horn <jann@thejh.net>, Josh Poimboeuf <jpoimboe@redhat.com>, Oleg Nesterov <oleg@redhat.com>, Andy Lutomirski <luto@kernel.org> Subject: [PATCH v2 3/8] kthread: to_live_kthread() needs try_get_task_stack() Date: Thu, 15 Sep 2016 22:45:44 -0700 Message-ID: <cb9b16bbc19d4aea4507ab0552e4644c1211d130.1474003868.git.luto@kernel.org> (raw) In-Reply-To: <cover.1474003868.git.luto@kernel.org> In-Reply-To: <cover.1474003868.git.luto@kernel.org> From: Oleg Nesterov <oleg@redhat.com> get_task_struct(tsk) no longer pins tsk->stack so all users of to_live_kthread() should do try_get_task_stack/put_task_stack to protect "struct kthread" which lives on kthread's stack. TODO: Kill to_live_kthread(), perhaps we can even kill "struct kthread" too, and rework kthread_stop(), it can use task_work_add() to sync with the exiting kernel thread. Message-Id: <20160629180357.GA7178@redhat.com> Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Andy Lutomirski <luto@kernel.org> --- kernel/kthread.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/kthread.c b/kernel/kthread.c index 9ff173dca1ae..4ab4c3766a80 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -64,7 +64,7 @@ static inline struct kthread *to_kthread(struct task_struct *k) static struct kthread *to_live_kthread(struct task_struct *k) { struct completion *vfork = ACCESS_ONCE(k->vfork_done); - if (likely(vfork)) + if (likely(vfork) && try_get_task_stack(k)) return __to_kthread(vfork); return NULL; } @@ -425,8 +425,10 @@ void kthread_unpark(struct task_struct *k) { struct kthread *kthread = to_live_kthread(k); - if (kthread) + if (kthread) { __kthread_unpark(k, kthread); + put_task_stack(k); + } } EXPORT_SYMBOL_GPL(kthread_unpark); @@ -455,6 +457,7 @@ int kthread_park(struct task_struct *k) wait_for_completion(&kthread->parked); } } + put_task_stack(k); ret = 0; } return ret; @@ -490,6 +493,7 @@ int kthread_stop(struct task_struct *k) __kthread_unpark(k, kthread); wake_up_process(k); wait_for_completion(&kthread->exited); + put_task_stack(k); } ret = k->exit_code; put_task_struct(k); -- 2.7.4
next prev parent reply index Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top 2016-09-16 5:45 [PATCH v2 0/8] thread_info cleanups and stack caching Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 1/8] x86/entry/64: Fix a minor comment rebase error Andy Lutomirski 2016-09-16 9:16 ` [tip:x86/asm] " tip-bot for Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 2/8] sched: Add try_get_task_stack() and put_task_stack() Andy Lutomirski 2016-09-16 9:16 ` [tip:x86/asm] sched/core: " tip-bot for Andy Lutomirski 2016-09-16 5:45 ` Andy Lutomirski [this message] 2016-09-16 9:17 ` [tip:x86/asm] kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function tip-bot for Oleg Nesterov 2016-09-16 5:45 ` [PATCH v2 4/8] x86/dumpstack: Pin the target stack when dumping it Andy Lutomirski 2016-09-16 9:17 ` [tip:x86/asm] " tip-bot for Andy Lutomirski 2016-09-16 11:55 ` Josh Poimboeuf 2016-09-16 12:28 ` Josh Poimboeuf 2016-09-16 12:57 ` Ingo Molnar 2016-09-16 13:05 ` [PATCH] x86/dumpstack: remove NULL task pointer convention Josh Poimboeuf 2016-09-16 5:45 ` [PATCH v2 5/8] x86/process: Pin the target stack in get_wchan() Andy Lutomirski 2016-09-16 9:18 ` [tip:x86/asm] " tip-bot for Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 6/8] lib/syscall: Pin the task stack in collect_syscall() Andy Lutomirski 2016-09-16 9:18 ` [tip:x86/asm] " tip-bot for Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 7/8] sched: Free the stack early if CONFIG_THREAD_INFO_IN_TASK Andy Lutomirski 2016-09-16 9:19 ` [tip:x86/asm] sched/core: " tip-bot for Andy Lutomirski 2016-09-16 5:45 ` [PATCH v2 8/8] fork: Cache two thread stacks per cpu if CONFIG_VMAP_STACK is set Andy Lutomirski 2016-09-16 9:19 ` [tip:x86/asm] fork: Optimize task creation by caching two thread stacks per CPU if CONFIG_VMAP_STACK=y tip-bot for Andy Lutomirski
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