Discourage drivers/modules to be creative with preemption. Sadly all is implemented in macros and inline so if they want to do evil they still can, but at least try and discourage some.
Cc: Eliezer Tamir <[email protected]> Cc: [email protected] Cc: [email protected] Cc: Mike Galbraith <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: [email protected] Cc: Rusty Russell <[email protected]> Cc: Arjan van de Ven <[email protected]> Cc: [email protected] Cc: [email protected] Reviewed-by: Thomas Gleixner <[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> --- include/linux/preempt.h | 22 ++++++++++++++++++++-- include/linux/uaccess.h | 5 ++++- 2 files changed, 24 insertions(+), 3 deletions(-) --- a/include/linux/preempt.h +++ b/include/linux/preempt.h @@ -64,7 +64,11 @@ do { \ } while (0) #else -#define preempt_enable() preempt_enable_no_resched() +#define preempt_enable() \ +do { \ + barrier(); \ + preempt_count_dec(); \ +} while (0) #define preempt_check_resched() do { } while (0) #endif @@ -93,7 +97,11 @@ 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 */ @@ -126,6 +134,16 @@ do { \ #define preempt_fold_need_resched() do { } while (0) #endif +#ifdef MODULE +/* + * Modules have no business playing preemption tricks. + */ +#undef sched_preempt_enable_no_resched +#undef preempt_enable_no_resched +#undef preempt_enable_no_resched_notrace +#undef preempt_check_resched +#endif + #ifdef CONFIG_PREEMPT_NOTIFIERS struct preempt_notifier; --- a/include/linux/uaccess.h +++ b/include/linux/uaccess.h @@ -25,13 +25,16 @@ static inline void pagefault_disable(voi 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
