Messages in this thread Patch in this message | | | From | Heinrich Schuchardt <> | Subject | [PATCH 1/4 v4] kernel/fork.c: new function for max_threads | Date | Mon, 23 Feb 2015 21:14:34 +0100 |
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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 <xypron.glpk@gmx.de> --- 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
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