Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752519AbbBWUPc (ORCPT ); Mon, 23 Feb 2015 15:15:32 -0500 Received: from mout.gmx.net ([212.227.15.15]:61492 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751601AbbBWUPb (ORCPT ); Mon, 23 Feb 2015 15:15:31 -0500 From: Heinrich Schuchardt To: Andrew Morton Cc: Aaron Tomlin , Andy Lutomirski , Davidlohr Bueso , David Rientjes , "David S. Miller" , Fabian Frederick , Guenter Roeck , "H. Peter Anvin" , Ingo Molnar , Jens Axboe , Joe Perches , Johannes Weiner , Kees Cook , Michael Marineau , Oleg Nesterov , "Paul E. McKenney" , Peter Zijlstra , Prarit Bhargava , Rik van Riel , Rusty Russell , Steven Rostedt , Thomas Gleixner , Vladimir Davydov , linux-kernel@vger.kernel.org, Heinrich Schuchardt Subject: [PATCH 1/4 v4] kernel/fork.c: new function for max_threads Date: Mon, 23 Feb 2015 21:14:34 +0100 Message-Id: <1424722477-23758-2-git-send-email-xypron.glpk@gmx.de> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1424722477-23758-1-git-send-email-xypron.glpk@gmx.de> References: <20150222075825.GA20626@gmail.com> <1424722477-23758-1-git-send-email-xypron.glpk@gmx.de> X-Provags-ID: V03:K0:xFCb6dEs8kgkVDxqp/ZAi2kvlHxcfe5eu0PYtX3I8JxPview11O /nA+xgEjvCXn7HjkvC5i+xyaWn9fE2BWCCAXUI7w0Nyzu+j7gLfHRn6Qjq+o1R8QsQbSGCN bgLWuhOoRntfbXDqoPYRQA71NEcCjfm54OPOmMRdA2u830yX/KmD+BLwsX6hsBpouqjho5F mrAZrjNdkxgDaoo8DMOTw== X-UI-Out-Filterresults: notjunk:1; Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3559 Lines: 117 PAGE_SIZE is not guaranteed to be equal to or less than 8 times the THREAD_SIZE. E.g. architecture hexagon may have page size 1M and thread size 4096. This would lead to a division by zero in the calculation of max_threads. With this patch the buggy code is moved to a separate function set_max_threads. The error is not fixed. After fixing the problem in a separate patch the new function can be reused to adjust max_threads after adding or removing memory. Argument mempages of function fork_init() is removed as totalram_pages is an exported symbol. The creation of separate patches for refactoring to a new function and for fixing the logic was requested by Ingo Molnar. Signed-off-by: Heinrich Schuchardt --- init/main.c | 4 ++-- kernel/fork.c | 39 ++++++++++++++++++++++++--------------- 2 files changed, 26 insertions(+), 17 deletions(-) diff --git a/init/main.c b/init/main.c index 61b99376..21394ec 100644 --- a/init/main.c +++ b/init/main.c @@ -94,7 +94,7 @@ static int kernel_init(void *); extern void init_IRQ(void); -extern void fork_init(unsigned long); +extern void fork_init(void); extern void radix_tree_init(void); #ifndef CONFIG_DEBUG_RODATA static inline void mark_rodata_ro(void) { } @@ -655,7 +655,7 @@ asmlinkage __visible void __init start_kernel(void) #endif thread_info_cache_init(); cred_init(); - fork_init(totalram_pages); + fork_init(); proc_caches_init(); buffer_init(); key_init(); diff --git a/kernel/fork.c b/kernel/fork.c index 4dc2dda..3a423b2 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -253,27 +253,18 @@ EXPORT_SYMBOL_GPL(__put_task_struct); void __init __weak arch_task_cache_init(void) { } -void __init fork_init(unsigned long mempages) +/* + * set_max_threads + * The argument is ignored. + */ +static void set_max_threads(unsigned int max_threads_suggested) { -#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR -#ifndef ARCH_MIN_TASKALIGN -#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES -#endif - /* create a slab on which task_structs can be allocated */ - task_struct_cachep = - kmem_cache_create("task_struct", sizeof(struct task_struct), - ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); -#endif - - /* do the arch specific task caches init */ - arch_task_cache_init(); - /* * The default maximum number of threads is set to a safe * value: the thread structures can take up at most half * of memory. */ - max_threads = mempages / (8 * THREAD_SIZE / PAGE_SIZE); + max_threads = totalram_pages / (8 * THREAD_SIZE / PAGE_SIZE); /* * we need to allow at least 20 threads to boot a system @@ -287,6 +278,24 @@ void __init fork_init(unsigned long mempages) init_task.signal->rlim[RLIMIT_NPROC]; } +void __init fork_init(void) +{ +#ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR +#ifndef ARCH_MIN_TASKALIGN +#define ARCH_MIN_TASKALIGN L1_CACHE_BYTES +#endif + /* create a slab on which task_structs can be allocated */ + task_struct_cachep = + kmem_cache_create("task_struct", sizeof(struct task_struct), + ARCH_MIN_TASKALIGN, SLAB_PANIC | SLAB_NOTRACK, NULL); +#endif + + /* do the arch specific task caches init */ + arch_task_cache_init(); + + set_max_threads(UINT_MAX); +} + int __weak arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) { -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/