Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752360AbbBXTj7 (ORCPT ); Tue, 24 Feb 2015 14:39:59 -0500 Received: from mout.gmx.net ([212.227.17.20]:51827 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751605AbbBXTj6 (ORCPT ); Tue, 24 Feb 2015 14:39:58 -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 1/3 v5] kernel/fork.c: new function for max_threads Date: Tue, 24 Feb 2015 20:38:19 +0100 Message-Id: <1424806701-30099-2-git-send-email-xypron.glpk@gmx.de> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1424806701-30099-1-git-send-email-xypron.glpk@gmx.de> References: <1424722477-23758-1-git-send-email-xypron.glpk@gmx.de> <1424806701-30099-1-git-send-email-xypron.glpk@gmx.de> X-Provags-ID: V03:K0:9tU636mlb6gyc08GCxLpRT5aNVHR7S9kyTXzlVj2UH5um6X6hG9 gR4dCsZI8rIKrEEUr0QWGLTe3IxOu/ckmBxj0k1N+3ECMeitpawflSbjZ+qGazV2t1w0YFx +y8Xm2ni7179J6+P0VmnHCcWRw359H+7PszlJY98N0Wmmexbzc8Byz04gP/f8zHwcALCohi FOKefv9miZDkRQ/GeOqkg== 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: 3176 Lines: 107 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 suggested by Ingo Molnar. Signed-off-by: Heinrich Schuchardt --- init/main.c | 4 ++-- kernel/fork.c | 35 ++++++++++++++++++++++------------- 2 files changed, 24 insertions(+), 15 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..460b044 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -253,7 +253,27 @@ 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) +{ + /* + * 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 = totalram_pages / (8 * THREAD_SIZE / PAGE_SIZE); + + /* + * we need to allow at least 20 threads to boot a system + */ + if (max_threads < 20) + max_threads = 20; +} + +void __init fork_init(void) { #ifndef CONFIG_ARCH_TASK_STRUCT_ALLOCATOR #ifndef ARCH_MIN_TASKALIGN @@ -268,18 +288,7 @@ void __init fork_init(unsigned long mempages) /* 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); - - /* - * we need to allow at least 20 threads to boot a system - */ - if (max_threads < 20) - max_threads = 20; + set_max_threads(UINT_MAX); init_task.signal->rlim[RLIMIT_NPROC].rlim_cur = max_threads/2; init_task.signal->rlim[RLIMIT_NPROC].rlim_max = max_threads/2; -- 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/