Re: [PATCH 7/7] preempt: Take away preempt_enable_no_resched() from modules

Peter Zijlstra
2013-11-20T19:18:52Z

On Wed, Nov 20, 2013 at 10:54:57AM -0800, Jacob Pan wrote:
> run into a couple of compile issues.
>
> 1)
> include/linux/rcupdate.h: In function ‘rcu_read_unlock_sched_notrace’:
> include/linux/rcupdate.h:889:2: error: implicit declaration of function
> ‘preempt_enable_no_resched_notrace’ [-Werror=implicit-function-declaration]
>
> 2)
> In file included from drivers/cpufreq/acpi-cpufreq.c:41:0:
> include/linux/uaccess.h: In function ‘pagefault_enable’:
> include/linux/uaccess.h:34:2: error: implicit declaration of function
> ‘preempt_check_resched’ [-Werror=implicit-function-declaration]
>
> 1) happens when CONFIG_PREEMPT is not set, perhaps add a dummy function?
> 2) I am not sure if we should take pagefault_enable away from modules

I think the below will cure both -- will fold in the proper patches
tomorrow, need to get away from the computer noaw.

---
include/linux/preempt.h | 6 +++++-
include/linux/uaccess.h | 5 ++++-
2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index a3d9dc8c2c00..41bc3fc4cdc5 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -93,7 +93,11 @@ do { \
__preempt_schedule_context(); \
} while (0)
#else
-#define preempt_enable_notrace() preempt_enable_no_resched_notrace()
+#define preempt_enable_notrace() \
+do { \
+ barrier(); \
+ __preempt_count_dec(); \
+} while (0)
#endif

#else /* !CONFIG_PREEMPT_COUNT */
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 9d8cf056e661..ecd3319dac33 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -25,13 +25,16 @@ static inline void pagefault_disable(void)

static inline void pagefault_enable(void)
{
+#ifndef CONFIG_PREEMPT
/*
* make sure to issue those last loads/stores before enabling
* the pagefault handler again.
*/
barrier();
preempt_count_dec();
- preempt_check_resched();
+#else
+ preempt_enable();
+#endif
}

#ifndef ARCH_HAS_NOCACHE_UACCESS