On Tue, Nov 19, 2013 at 03:51:43PM +0100, Peter Zijlstra wrote:
> That said, that drive is completely wrecked. It uses
> preempt_enable_no_resched() wrong too, it has uncommented barriers..
>
> Dude, wtf are you guys smoking?
---
Subject: sched: Take away preempt_enable_no_resched() and friends from modules
There is no way in hell modules are going to play preemption tricks like
this.
Cc: eliezer.tamir@xxxxxxxxxxxxxxx
Cc: arjan@xxxxxxxxxxxxxxx
Reviewed-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
drivers/thermal/intel_powerclamp.c | 2 +-
include/linux/preempt.h | 8 +++++++-
include/net/busy_poll.h | 15 +++------------
3 files changed, 11 insertions(+), 14 deletions(-)
diff --git a/drivers/thermal/intel_powerclamp.c b/drivers/thermal/intel_powerclamp.c
index 8f181b3f842b..0a12ddc2eb4c 100644
--- a/drivers/thermal/intel_powerclamp.c
+++ b/drivers/thermal/intel_powerclamp.c
@@ -445,7 +445,7 @@ static int clamp_thread(void *arg)
atomic_inc(&idle_wakeup_counter);
}
tick_nohz_idle_exit();
- preempt_enable_no_resched();
+ preempt_enable();
}
del_timer_sync(&wakeup_timer);
clear_bit(cpunr, cpu_clamping_mask);
diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index a3d9dc8c2c00..3ed2b5335ab4 100644
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -64,7 +64,7 @@ do { \
} while (0)
#else
-#define preempt_enable() preempt_enable_no_resched()
+#define preempt_enable() sched_preempt_enable_no_resched()
#define preempt_check_resched() do { } while (0)
#endif
@@ -116,6 +116,12 @@ do { \
#endif /* CONFIG_PREEMPT_COUNT */
+#ifdef MODULE
+#undef preempt_enable_no_resched
+#undef preempt_enable_no_resched_notrace
+#undef preempt_check_resched
+#endif
+
#ifdef CONFIG_PREEMPT_NOTIFIERS
struct preempt_notifier;
diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index 829627d7b846..756827a86c2d 100644
--- a/include/net/busy_poll.h
+++ b/include/net/busy_poll.h
@@ -42,27 +42,18 @@ static inline bool net_busy_loop_on(void)
return sysctl_net_busy_poll;
}
-/* a wrapper to make debug_smp_processor_id() happy
- * we can use sched_clock() because we don't care much about precision
- * we only care that the average is bounded
- */
-#ifdef CONFIG_DEBUG_PREEMPT
static inline u64 busy_loop_us_clock(void)
{
u64 rc;
+ /* XXX with interrupts enabled sched_clock() can return utter garbage */
+
preempt_disable_notrace();
rc = sched_clock();
- preempt_enable_no_resched_notrace();
+ preempt_enable_notrace();
return rc >> 10;
}
-#else /* CONFIG_DEBUG_PREEMPT */
-static inline u64 busy_loop_us_clock(void)
-{
- return sched_clock() >> 10;
-}
-#endif /* CONFIG_DEBUG_PREEMPT */
static inline unsigned long sk_busy_loop_end_time(struct sock *sk)
{
--
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