| Message ID | 20131120162736.760865926@infradead.org (mailing list archive) |
|---|---|
| State | Not Applicable, archived |
| Headers | show |
On Wed, 20 Nov 2013 17:04:57 +0100 Peter Zijlstra <peterz@infradead.org> wrote: > 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: Rusty Russell <rusty@rustcorp.com.au> > Cc: Arjan van de Ven <arjan@linux.intel.com> > Cc: lenb@kernel.org > Cc: rjw@rjwysocki.net > Cc: Eliezer Tamir <eliezer.tamir@linux.intel.com> > Cc: Chris Leech <christopher.leech@intel.com> > Cc: David S. Miller <davem@davemloft.net> > Cc: rui.zhang@intel.com > Cc: jacob.jun.pan@linux.intel.com > Cc: Mike Galbraith <bitbucket@online.de> > Cc: Ingo Molnar <mingo@kernel.org> > Cc: hpa@zytor.com > Reviewed-by: Thomas Gleixner <tglx@linutronix.de> > Signed-off-by: Peter Zijlstra <peterz@infradead.org> > --- > include/linux/preempt.h | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > --- 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 > > @@ -126,6 +130,16 @@ 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; > > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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? Ah, indeed, will fix. > 2) I am not sure if we should take pagefault_enable away from modules We can't I think, I'll have to fix that up. Easiest would be to make preempt_check_resched() available again. That function actually adds preemption points so its not bad. -- To unsubscribe from this list: send the line "unsubscribe linux-pm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
--- 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 @@ -126,6 +130,16 @@ 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;