The patch titled
Subject: kernel/fork.c: new function for max_threads
has been added to the -mm tree. Its filename is
kernel-forkc-new-function-for-max_threads.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/kernel-forkc-new-function-for-max_threads.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/kernel-forkc-new-function-for-max_threads.patch
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------------------------------------------------------
From: Heinrich Schuchardt <xypron.glpk@xxxxxx>
Subject: kernel/fork.c: new function for max_threads
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>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Guenter Roeck <linux@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
init/main.c | 4 ++--
kernel/fork.c | 34 +++++++++++++++++++++-------------
2 files changed, 23 insertions(+), 15 deletions(-)
diff -puN init/main.c~kernel-forkc-new-function-for-max_threads init/main.c
--- a/init/main.c~kernel-forkc-new-function-for-max_threads
+++ a/init/main.c
@@ -91,7 +91,7 @@
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) { }
@@ -644,7 +644,7 @@ asmlinkage __visible void __init start_k
#endif
thread_info_cache_init();
cred_init();
- fork_init(totalram_pages);
+ fork_init();
proc_caches_init();
buffer_init();
key_init();
diff -puN kernel/fork.c~kernel-forkc-new-function-for-max_threads kernel/fork.c
--- a/kernel/fork.c~kernel-forkc-new-function-for-max_threads
+++ a/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 one
+ * eighth of the 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 memp
/* 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 one
- * eighth of the 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;
_
Patches currently in -mm which might be from xypron.glpk@xxxxxx are
kernel-forkc-new-function-for-max_threads.patch
kernel-forkc-avoid-division-by-zero.patch
kernel-forkc-avoid-division-by-zero-fix.patch
kernel-sysctlc-threads-max-observe-limits.patch
doc-sysctl-kerneltxt-document-threads-max.patch
doc-sysctl-kerneltxt-document-threads-max-fix.patch
linux-next.patch
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