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@xxxxxx>
---
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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