Messages in this thread Patch in this message | | | Date | Sat, 10 Aug 2002 18:27:31 -0700 | From | Andrew Morton <> | Subject | Re: [patch 6/12] hold atomic kmaps across generic_file_read |
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Linus Torvalds wrote: > > On Sat, 10 Aug 2002, Andrew Morton wrote: > > > > If not, I don't think it's worth making this change just for > > the highmem read/write thing (calculating `current' at each > > spin_lock site...) I just open coded it. > > Well, this way it will now do the preempt count twice (once in > kmap_atomic, once in th eopen-coded one) if preempt is enabled. > > I'd suggest just making k[un]map_atomic() always do the > inc/dec_preempt_count. Other ideas? >
Well the optimum solution there would be to create and use `inc_preempt_count_non_preempt()'. I don't see any way of embedding this in kmap_atomic() or copy_to_user_atomic() without loss of flexibility or incurring a double-inc somewhere.
Please let my post-virginal brain know if you're not otherwise OK with the approach ;)
arch/i386/mm/fault.c | 6 +++--- include/linux/preempt.h | 24 ++++++++++++++++++++++-- 2 files changed, 25 insertions(+), 5 deletions(-)
--- 2.5.30/arch/i386/mm/fault.c~atomic-copy_user Sat Aug 10 14:44:03 2002 +++ 2.5.30-akpm/arch/i386/mm/fault.c Sat Aug 10 14:44:52 2002 @@ -189,10 +189,10 @@ asmlinkage void do_page_fault(struct pt_ info.si_code = SEGV_MAPERR; /* - * If we're in an interrupt or have no user - * context, we must not take the fault.. + * If we're in an interrupt, have no user context or are running in an + * atomic region then we must not take the fault.. */ - if (in_interrupt() || !mm) + if (preempt_count() || !mm) goto no_context; #ifdef CONFIG_X86_REMOTE_DEBUG --- 2.5.30/include/linux/preempt.h~atomic-copy_user Sat Aug 10 16:18:50 2002 +++ 2.5.30-akpm/include/linux/preempt.h Sat Aug 10 18:23:40 2002 @@ -5,19 +5,29 @@ #define preempt_count() (current_thread_info()->preempt_count) +#define inc_preempt_count() \ +do { \ + preempt_count()++; \ +} while (0) + +#define dec_preempt_count() \ +do { \ + preempt_count()--; \ +} while (0) + #ifdef CONFIG_PREEMPT extern void preempt_schedule(void); #define preempt_disable() \ do { \ - preempt_count()++; \ + inc_preempt_count(); \ barrier(); \ } while (0) #define preempt_enable_no_resched() \ do { \ - preempt_count()--; \ + dec_preempt_count(); \ barrier(); \ } while (0) @@ -34,6 +44,9 @@ do { \ preempt_schedule(); \ } while (0) +#define inc_preempt_count_non_preempt() do { } while (0) +#define dec_preempt_count_non_preempt() do { } while (0) + #else #define preempt_disable() do { } while (0) @@ -41,6 +54,13 @@ do { \ #define preempt_enable() do { } while (0) #define preempt_check_resched() do { } while (0) +/* + * Sometimes we want to increment the preempt count, but we know that it's + * already incremented if the kernel is compiled for preemptibility. + */ +#define inc_preempt_count_non_preempt() inc_preempt_count() +#define dec_preempt_count_non_preempt() dec_preempt_count() + #endif #endif /* __LINUX_PREEMPT_H */ . - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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