From nobody Thu Jun 25 08:29:14 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C81EC433F5 for ; Tue, 22 Feb 2022 21:27:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235957AbiBVV1x (ORCPT ); Tue, 22 Feb 2022 16:27:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44062 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235802AbiBVV1b (ORCPT ); Tue, 22 Feb 2022 16:27:31 -0500 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6A04B8E187; Tue, 22 Feb 2022 13:27:05 -0800 (PST) Date: Tue, 22 Feb 2022 21:27:03 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1645565224; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=L2SftizOYJm0Oa3oZMe4lwD8sUSmZAIEP8u+0K0p48o=; b=QtQKhdvBssqDSxlFOd100wKw34gpXxODx6UjNLxvm0ld/3RQlyByF80RftK6E2LqC26hWq kCBN32TeZUHJKYNj4PR2s1BG92kUgWIiD/d4sChbk9OsE7wp+Wn6JEmPhVwpyz0K6kHf6c 8hg/vP6HJ6dhqDifHIRtzivMK7lrtjAeVCWnlUdq2a++33HHosSwAVwxJSjMpgZj71r022 MRWoOOCxwZcJkCQPda9rYJ9dObACQT6eRCzYa6NRhfC5J88KsLUmr6s6iQFZUkOAheDaqz 67lmVQQboqw1Op2tFG2Q2lGWo3uOyoUz1DqlyYNjm6tA/BfuH8nv0/twxTaMUw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1645565224; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=L2SftizOYJm0Oa3oZMe4lwD8sUSmZAIEP8u+0K0p48o=; b=r4aZx67naC9SVbdsBBF+bA6wRYiTENbpyGoW0BXwZGU/DUm9HgLwwwhbBsRR0LzXuNtcjT tkzCwH3rtycrnCAg== From: "tip-bot2 for Sebastian Andrzej Siewior" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: core/core] fork: Redo ifdefs around task stack handling Cc: Sebastian Andrzej Siewior , Thomas Gleixner , Andy Lutomirski , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20220217102406.3697941-2-bigeasy@linutronix.de> References: <20220217102406.3697941-2-bigeasy@linutronix.de> MIME-Version: 1.0 Message-ID: <164556522311.16921.16318571180509187723.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the core/core branch of tip: Commit-ID: be9a2277cafd318976d59c41a7f45a934ec43b26 Gitweb: https://git.kernel.org/tip/be9a2277cafd318976d59c41a7f45a934= ec43b26 Author: Sebastian Andrzej Siewior AuthorDate: Thu, 17 Feb 2022 11:23:59 +01:00 Committer: Thomas Gleixner CommitterDate: Tue, 22 Feb 2022 22:25:01 +01:00 fork: Redo ifdefs around task stack handling The use of ifdef CONFIG_VMAP_STACK is confusing in terms what is actually happenning and what can happen. For instance from reading free_thread_stack() it appears that in the CONFIG_VMAP_STACK case it may receive a non-NULL vm pointer but it may also be NULL in which case __free_pages() is used to free the stack. This is however not the case because in the VMAP case a non-NULL pointer is always returned here. Since it looks like this might happen, the compiler creates the correct dead code with the invocation to __free_pages() and everything around it. Twice. Add spaces between the ifdef and the identifer to recognize the ifdef level which is currently in scope. Add the current identifer as a comment behind #else and #endif. Move the code within free_thread_stack() and alloc_thread_stack_node() into the relevant ifdef blocks. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Acked-by: Andy Lutomirski Link: https://lore.kernel.org/r/20220217102406.3697941-2-bigeasy@linutronix= .de --- kernel/fork.c | 74 ++++++++++++++++++++++++++------------------------ 1 file changed, 39 insertions(+), 35 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index a024bf6..f5cc101 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -185,7 +185,7 @@ static inline void free_task_struct(struct task_struct = *tsk) */ # if THREAD_SIZE >=3D PAGE_SIZE || defined(CONFIG_VMAP_STACK) =20 -#ifdef CONFIG_VMAP_STACK +# ifdef CONFIG_VMAP_STACK /* * vmalloc() is a bit slow, and calling vfree() enough times will force a = TLB * flush. Try to minimize the number of calls by caching stacks. @@ -210,11 +210,9 @@ static int free_vm_stack_cache(unsigned int cpu) =20 return 0; } -#endif =20 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int= node) { -#ifdef CONFIG_VMAP_STACK void *stack; int i; =20 @@ -258,45 +256,53 @@ static unsigned long *alloc_thread_stack_node(struct = task_struct *tsk, int node) tsk->stack =3D stack; } return stack; -#else - struct page *page =3D alloc_pages_node(node, THREADINFO_GFP, - THREAD_SIZE_ORDER); - - if (likely(page)) { - tsk->stack =3D kasan_reset_tag(page_address(page)); - return tsk->stack; - } - return NULL; -#endif } =20 -static inline void free_thread_stack(struct task_struct *tsk) +static void free_thread_stack(struct task_struct *tsk) { -#ifdef CONFIG_VMAP_STACK struct vm_struct *vm =3D task_stack_vm_area(tsk); + int i; =20 - if (vm) { - int i; + for (i =3D 0; i < THREAD_SIZE / PAGE_SIZE; i++) + memcg_kmem_uncharge_page(vm->pages[i], 0); =20 - for (i =3D 0; i < THREAD_SIZE / PAGE_SIZE; i++) - memcg_kmem_uncharge_page(vm->pages[i], 0); + for (i =3D 0; i < NR_CACHED_STACKS; i++) { + if (this_cpu_cmpxchg(cached_stacks[i], NULL, + tsk->stack_vm_area) !=3D NULL) + continue; =20 - for (i =3D 0; i < NR_CACHED_STACKS; i++) { - if (this_cpu_cmpxchg(cached_stacks[i], - NULL, tsk->stack_vm_area) !=3D NULL) - continue; + tsk->stack =3D NULL; + tsk->stack_vm_area =3D NULL; + return; + } + vfree_atomic(tsk->stack); + tsk->stack =3D NULL; + tsk->stack_vm_area =3D NULL; +} =20 - return; - } +# else /* !CONFIG_VMAP_STACK */ =20 - vfree_atomic(tsk->stack); - return; +static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int= node) +{ + struct page *page =3D alloc_pages_node(node, THREADINFO_GFP, + THREAD_SIZE_ORDER); + + if (likely(page)) { + tsk->stack =3D kasan_reset_tag(page_address(page)); + return tsk->stack; } -#endif + return NULL; +} =20 +static void free_thread_stack(struct task_struct *tsk) +{ __free_pages(virt_to_page(tsk->stack), THREAD_SIZE_ORDER); + tsk->stack =3D NULL; } -# else + +# endif /* CONFIG_VMAP_STACK */ +# else /* !(THREAD_SIZE >=3D PAGE_SIZE || defined(CONFIG_VMAP_STACK)) */ + static struct kmem_cache *thread_stack_cache; =20 static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, @@ -312,6 +318,7 @@ static unsigned long *alloc_thread_stack_node(struct ta= sk_struct *tsk, static void free_thread_stack(struct task_struct *tsk) { kmem_cache_free(thread_stack_cache, tsk->stack); + tsk->stack =3D NULL; } =20 void thread_stack_cache_init(void) @@ -321,8 +328,9 @@ void thread_stack_cache_init(void) THREAD_SIZE, NULL); BUG_ON(thread_stack_cache =3D=3D NULL); } -# endif -#endif + +# endif /* THREAD_SIZE >=3D PAGE_SIZE || defined(CONFIG_VMAP_STACK) */ +#endif /* !CONFIG_ARCH_THREAD_STACK_ALLOCATOR */ =20 /* SLAB cache for signal_struct structures (tsk->signal) */ static struct kmem_cache *signal_cachep; @@ -432,10 +440,6 @@ static void release_task_stack(struct task_struct *tsk) =20 account_kernel_stack(tsk, -1); free_thread_stack(tsk); - tsk->stack =3D NULL; -#ifdef CONFIG_VMAP_STACK - tsk->stack_vm_area =3D NULL; -#endif } =20 #ifdef CONFIG_THREAD_INFO_IN_TASK