[PATCH 1/2] explicitly allocate thread stack

From: Roman Zippel
Date: Sun Sep 05 2004 - 14:13:30 EST

Hi,

Right now we somewhat hide the stack allocation, so this patch renames
alloc_thread_info into alloc_thread_stack and removes the (luckily unused)
get_thread_info/put_thread_info. It also removes the knowledge in generic
code that the stack is after the thread_info.
This patch only has the changes i386/m68k, but the rest is easy to do.

bye, Roman

diff -ur linux-2.6.8.1/include/asm-i386/thread_info.h linux-2.6.8.1-allocstack/include/asm-i386/thread_info.h
--- linux-2.6.8.1/include/asm-i386/thread_info.h 2004-06-16 20:16:44.000000000 +0200
+++ linux-2.6.8.1-allocstack/include/asm-i386/thread_info.h 2004-09-05 13:51:35.000000000 +0200
@@ -99,9 +99,9 @@
return ti;
}

-/* thread information allocation */
+/* thread information/stack allocation */
#ifdef CONFIG_DEBUG_STACK_USAGE
-#define alloc_thread_info(tsk) \
+#define alloc_thread_stack() \
({ \
struct thread_info *ret; \
\
@@ -111,12 +111,18 @@
ret; \
})
#else
-#define alloc_thread_info(tsk) kmalloc(THREAD_SIZE, GFP_KERNEL)
+#define alloc_thread_stack() kmalloc(THREAD_SIZE, GFP_KERNEL)
#endif
+#define free_thread_stack(stk) kfree(stk)

-#define free_thread_info(info) kfree(info)
-#define get_thread_info(ti) get_task_struct((ti)->task)
-#define put_thread_info(ti) put_task_struct((ti)->task)
+#define initialize_thread_info(tsk, orig) \
+ ({ \
+ struct thread_info *ti = tsk->stack; \
+ \
+ *ti = *orig->thread_info; \
+ ti->task = tsk; \
+ tsk->thread_info = ti; \
+ })

#else /* !__ASSEMBLY__ */

diff -ur linux-2.6.8.1/include/asm-m68k/thread_info.h linux-2.6.8.1-allocstack/include/asm-m68k/thread_info.h
--- linux-2.6.8.1/include/asm-m68k/thread_info.h 2004-06-16 20:16:45.000000000 +0200
+++ linux-2.6.8.1-allocstack/include/asm-m68k/thread_info.h 2004-08-28 03:48:51.000000000 +0200
@@ -26,19 +26,32 @@
}, \
}

-/* THREAD_SIZE should be 8k, so handle differently for 4k and 8k machines */
-#if PAGE_SHIFT == 13 /* 8k machines */
-#define alloc_thread_info(tsk) ((struct thread_info *)__get_free_pages(GFP_KERNEL,0))
-#define free_thread_info(ti) free_pages((unsigned long)(ti),0)
-#else /* otherwise assume 4k pages */
-#define alloc_thread_info(tsk) ((struct thread_info *)__get_free_pages(GFP_KERNEL,1))
-#define free_thread_info(ti) free_pages((unsigned long)(ti),1)
-#endif /* PAGE_SHIFT == 13 */
+#ifdef CONFIG_DEBUG_STACK_USAGE
+#define alloc_thread_stack() \
+ ({ \
+ struct thread_info *ret; \
+ \
+ ret = kmalloc(THREAD_SIZE, GFP_KERNEL); \
+ if (ret) \
+ memset(ret, 0, THREAD_SIZE); \
+ ret; \
+ })
+#else
+#define alloc_thread_stack() kmalloc(THREAD_SIZE, GFP_KERNEL)
+#endif
+#define free_thread_stack(stk) kfree(stk)
+
+#define initialize_thread_info(tsk, orig) \
+ ({ \
+ struct thread_info *ti = &(tsk)->thread.info; \
+ \
+ ti->task = tsk; \
+ tsk->thread_info = &ti; \
+ })

-//#define init_thread_info (init_task.thread.info)
#define init_stack (init_thread_union.stack)

-#define current_thread_info() (current->thread_info)
+#define current_thread_info() (&current->thread.info)


#define __HAVE_THREAD_FUNCTIONS
diff -ur linux-2.6.8.1/include/linux/init_task.h linux-2.6.8.1-allocstack/include/linux/init_task.h
--- linux-2.6.8.1/include/linux/init_task.h 2004-08-14 12:53:36.000000000 +0200
+++ linux-2.6.8.1-allocstack/include/linux/init_task.h 2004-09-05 13:50:53.000000000 +0200
@@ -68,6 +68,7 @@
{ \
.state = 0, \
.thread_info = &init_thread_info, \
+ .stack = &init_stack, \
.usage = ATOMIC_INIT(2), \
.flags = 0, \
.lock_depth = -1, \
diff -ur linux-2.6.8.1/include/linux/sched.h linux-2.6.8.1-allocstack/include/linux/sched.h
--- linux-2.6.8.1/include/linux/sched.h 2004-08-14 12:53:36.000000000 +0200
+++ linux-2.6.8.1-allocstack/include/linux/sched.h 2004-09-05 13:38:30.000000000 +0200
@@ -390,6 +390,7 @@
struct task_struct {
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
struct thread_info *thread_info;
+ void *stack;
atomic_t usage;
unsigned long flags; /* per process flags, defined below */
unsigned long ptrace;
diff -ur linux-2.6.8.1/kernel/fork.c linux-2.6.8.1-allocstack/kernel/fork.c
--- linux-2.6.8.1/kernel/fork.c 2004-08-14 12:53:39.000000000 +0200
+++ linux-2.6.8.1-allocstack/kernel/fork.c 2004-08-28 03:11:02.000000000 +0200
@@ -70,14 +70,14 @@
}

#ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
-# define alloc_task_struct() kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
+# define alloc_task_struct(stk) kmem_cache_alloc(task_struct_cachep, GFP_KERNEL)
# define free_task_struct(tsk) kmem_cache_free(task_struct_cachep, (tsk))
static kmem_cache_t *task_struct_cachep;
#endif

static void free_task(struct task_struct *tsk)
{
- free_thread_info(tsk->thread_info);
+ free_thread_stack(tsk->stack);
free_task_struct(tsk);
}

@@ -241,24 +241,23 @@
static struct task_struct *dup_task_struct(struct task_struct *orig)
{
struct task_struct *tsk;
- struct thread_info *ti;
+ void *stack;

prepare_to_copy(orig);

- tsk = alloc_task_struct();
- if (!tsk)
+ stack = alloc_thread_stack();
+ if (!stack)
return NULL;

- ti = alloc_thread_info(tsk);
- if (!ti) {
- free_task_struct(tsk);
+ tsk = alloc_task_struct(stack);
+ if (!tsk) {
+ free_thread_stack(stack);
return NULL;
}

- *ti = *orig->thread_info;
*tsk = *orig;
- tsk->thread_info = ti;
- ti->task = tsk;
+ tsk->stack = stack;
+ initialize_thread_info(tsk, orig);

/* One for us, one for whoever does the "release_task()" (usually parent) */
atomic_set(&tsk->usage,2);
diff -ur linux-2.6.8.1/kernel/sched.c linux-2.6.8.1-allocstack/kernel/sched.c
--- linux-2.6.8.1/kernel/sched.c 2004-08-14 12:53:39.000000000 +0200
+++ linux-2.6.8.1-allocstack/kernel/sched.c 2004-09-05 13:37:12.000000000 +0200
@@ -3212,10 +3212,11 @@
#endif
#ifdef CONFIG_DEBUG_STACK_USAGE
{
- unsigned long * n = (unsigned long *) (p->thread_info+1);
+ unsigned long end = (unsigned long)p->stack + sizeof(struct thread_info);
+ unsigned long * n = (unsigned long *)end;
while (!*n)
n++;
- free = (unsigned long) n - (unsigned long)(p->thread_info+1);
+ free = (unsigned long) n - end;
}
#endif
printk("%5lu %5d %6d ", free, p->pid, p->parent->pid);
-
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