Re: 2.6.0-test7-mm1

From: Anton Blanchard (anton_at_samba.org)
Date: 10/16/03

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Date:	Fri, 17 Oct 2003 00:04:00 +1000
To: Ben Collins <bcollins@debian.org>

> > Anton had a ppc64 patch which implemented the preempt_count beancounting
> > without actually implementing premption. So might_sleep() does the right
> > thing.
>
> I might have to dig that out and try to make use of it. Thanks for the
> pointer.

Here is the patch with the ppc64 bits in it. (I already have
might_sleep() littered in asm-ppc64/semaphore.h and asm-ppc64/uaccess.h)

Its a bit old but it seems to dump valid warnings.

Anton

Sleep with spinlock debugging.

diff -puN arch/ppc64/Kconfig~spinlock_sleep arch/ppc64/Kconfig
--- foo/arch/ppc64/Kconfig~spinlock_sleep 2003-10-10 00:23:32.000000000 -0500
+++ foo-anton/arch/ppc64/Kconfig 2003-10-10 00:23:32.000000000 -0500
@@ -385,6 +385,13 @@ config DEBUG_PAGEALLOC
           This results in a large slowdown, but helps to find certain types
           of memory corruptions.

+config DEBUG_SPINLOCK_SLEEP
+ bool "Sleep-inside-spinlock checking"
+ depends on DEBUG_KERNEL
+ help
+ If you say Y here, various routines which may sleep will become very
+ noisy if they are called with a spinlock held.
+
endmenu

source "security/Kconfig"
diff -puN include/asm-ppc64/hardirq.h~spinlock_sleep include/asm-ppc64/hardirq.h
--- foo/include/asm-ppc64/hardirq.h~spinlock_sleep 2003-10-10 00:23:32.000000000 -0500
+++ foo-anton/include/asm-ppc64/hardirq.h 2003-10-10 00:23:32.000000000 -0500
@@ -82,7 +82,7 @@ typedef struct {

#define irq_enter() (preempt_count() += HARDIRQ_OFFSET)

-#ifdef CONFIG_PREEMPT
+#if defined(CONFIG_PREEMPT) || defined(CONFIG_DEBUG_SPINLOCK_SLEEP)
# define in_atomic() ((preempt_count() & ~PREEMPT_ACTIVE) != kernel_locked())
# define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1)
#else
diff -puN include/linux/preempt.h~spinlock_sleep include/linux/preempt.h
--- foo/include/linux/preempt.h~spinlock_sleep 2003-10-10 00:23:32.000000000 -0500
+++ foo-anton/include/linux/preempt.h 2003-10-10 00:23:32.000000000 -0500
@@ -24,6 +24,17 @@ do { \

extern void preempt_schedule(void);

+#define preempt_check_resched() \
+do { \
+ if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
+ preempt_schedule(); \
+} while (0)
+#else
+#define preempt_check_resched() do { } while (0)
+#endif
+
+#if defined(CONFIG_PREEMPT) || defined(CONFIG_DEBUG_SPINLOCK_SLEEP)
+
#define preempt_disable() \
do { \
         inc_preempt_count(); \
@@ -36,12 +47,6 @@ do { \
         barrier(); \
} while (0)

-#define preempt_check_resched() \
-do { \
- if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
- preempt_schedule(); \
-} while (0)
-
#define preempt_enable() \
do { \
         preempt_enable_no_resched(); \
diff -puN kernel/fork.c~spinlock_sleep kernel/fork.c
--- foo/kernel/fork.c~spinlock_sleep 2003-10-10 00:23:32.000000000 -0500
+++ foo-anton/kernel/fork.c 2003-10-10 00:23:32.000000000 -0500
@@ -850,7 +850,7 @@ struct task_struct *copy_process(unsigne
         if (p->binfmt && !try_module_get(p->binfmt->module))
                 goto bad_fork_cleanup_put_domain;

-#ifdef CONFIG_PREEMPT
+#if defined(CONFIG_PREEMPT) || defined(CONFIG_DEBUG_SPINLOCK_SLEEP)
         /*
          * schedule_tail drops this_rq()->lock so we compensate with a count
          * of 1. Also, we want to start with kernel preemption disabled.
diff -puN kernel/sched.c~spinlock_sleep kernel/sched.c
--- foo/kernel/sched.c~spinlock_sleep 2003-10-10 00:23:32.000000000 -0500
+++ foo-anton/kernel/sched.c 2003-10-10 00:23:32.000000000 -0500
@@ -2533,7 +2533,7 @@ void __init init_idle(task_t *idle, int
         local_irq_restore(flags);

         /* Set the preempt count _outside_ the spinlocks! */
-#ifdef CONFIG_PREEMPT
+#if defined(CONFIG_PREEMPT) || defined(CONFIG_DEBUG_SPINLOCK_SLEEP)
         idle->thread_info->preempt_count = (idle->lock_depth >= 0);
#else
         idle->thread_info->preempt_count = 0;

_
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