Messages in this thread Patch in this message | | | From | Heinrich Schuchardt <> | Subject | [PATCH 1/4 v6] kernel/fork.c: new function for max_threads | Date | Sun, 15 Mar 2015 17:13:35 +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 suggested by Ingo Molnar.
Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de> --- init/main.c | 4 ++-- kernel/fork.c | 34 +++++++++++++++++++++------------- 2 files changed, 23 insertions(+), 15 deletions(-)
diff --git a/init/main.c b/init/main.c index d4037ab..f470d14 100644 --- a/init/main.c +++ b/init/main.c @@ -93,7 +93,7 @@ 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) { } @@ -650,7 +650,7 @@ 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..bf1ff00 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -253,7 +253,26 @@ EXPORT_SYMBOL_GPL(__put_task_struct); void __init __weak arch_task_cache_init(void) { } -void __init fork_init(unsigned long mempages) +/* + * set_max_threads + */ +static void set_max_threads(void) +{ + /* + * 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 +287,7 @@ 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(); 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
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