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authorIngo Molnar <mingo@elte.hu>2005-06-21 17:14:34 -0700
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-21 18:46:13 -0700
commit39c715b71740c4a78ba4769fb54826929bac03cb (patch)
tree94dd679dfc8e6c2db65971739aa8c8c6206f8174 /include/linux/smp.h
parent84929801e14d968caeb84795bfbb88f04283fbd9 (diff)
[PATCH] smp_processor_id() cleanup
This patch implements a number of smp_processor_id() cleanup ideas that Arjan van de Ven and I came up with. The previous __smp_processor_id/_smp_processor_id/smp_processor_id API spaghetti was hard to follow both on the implementational and on the usage side. Some of the complexity arose from picking wrong names, some of the complexity comes from the fact that not all architectures defined __smp_processor_id. In the new code, there are two externally visible symbols: - smp_processor_id(): debug variant. - raw_smp_processor_id(): nondebug variant. Replaces all existing uses of _smp_processor_id() and __smp_processor_id(). Defined by every SMP architecture in include/asm-*/smp.h. There is one new internal symbol, dependent on DEBUG_PREEMPT: - debug_smp_processor_id(): internal debug variant, mapped to smp_processor_id(). Also, i moved debug_smp_processor_id() from lib/kernel_lock.c into a new lib/smp_processor_id.c file. All related comments got updated and/or clarified. I have build/boot tested the following 8 .config combinations on x86: {SMP,UP} x {PREEMPT,!PREEMPT} x {DEBUG_PREEMPT,!DEBUG_PREEMPT} I have also build/boot tested x64 on UP/PREEMPT/DEBUG_PREEMPT. (Other architectures are untested, but should work just fine.) Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Arjan van de Ven <arjan@infradead.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/linux/smp.h')
-rw-r--r--include/linux/smp.h40
1 files changed, 16 insertions, 24 deletions
diff --git a/include/linux/smp.h b/include/linux/smp.h
index dcf1db3b35d3..9dfa3ee769ae 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -92,10 +92,7 @@ void smp_prepare_boot_cpu(void);
/*
* These macros fold the SMP functionality into a single CPU system
*/
-
-#if !defined(__smp_processor_id) || !defined(CONFIG_PREEMPT)
-# define smp_processor_id() 0
-#endif
+#define raw_smp_processor_id() 0
#define hard_smp_processor_id() 0
#define smp_call_function(func,info,retry,wait) ({ 0; })
#define on_each_cpu(func,info,retry,wait) ({ func(info); 0; })
@@ -106,30 +103,25 @@ static inline void smp_send_reschedule(int cpu) { }
#endif /* !SMP */
/*
- * DEBUG_PREEMPT support: check whether smp_processor_id() is being
- * used in a preemption-safe way.
+ * smp_processor_id(): get the current CPU ID.
*
- * An architecture has to enable this debugging code explicitly.
- * It can do so by renaming the smp_processor_id() macro to
- * __smp_processor_id(). This should only be done after some minimal
- * testing, because usually there are a number of false positives
- * that an architecture will trigger.
+ * if DEBUG_PREEMPT is enabled the we check whether it is
+ * used in a preemption-safe way. (smp_processor_id() is safe
+ * if it's used in a preemption-off critical section, or in
+ * a thread that is bound to the current CPU.)
*
- * To fix a false positive (i.e. smp_processor_id() use that the
- * debugging code reports but which use for some reason is legal),
- * change the smp_processor_id() reference to _smp_processor_id(),
- * which is the nondebug variant. NOTE: don't use this to hack around
- * real bugs.
+ * NOTE: raw_smp_processor_id() is for internal use only
+ * (smp_processor_id() is the preferred variant), but in rare
+ * instances it might also be used to turn off false positives
+ * (i.e. smp_processor_id() use that the debugging code reports but
+ * which use for some reason is legal). Don't use this to hack around
+ * the warning message, as your code might not work under PREEMPT.
*/
-#ifdef __smp_processor_id
-# if defined(CONFIG_PREEMPT) && defined(CONFIG_DEBUG_PREEMPT)
- extern unsigned int smp_processor_id(void);
-# else
-# define smp_processor_id() __smp_processor_id()
-# endif
-# define _smp_processor_id() __smp_processor_id()
+#ifdef CONFIG_DEBUG_PREEMPT
+ extern unsigned int debug_smp_processor_id(void);
+# define smp_processor_id() debug_smp_processor_id()
#else
-# define _smp_processor_id() smp_processor_id()
+# define smp_processor_id() raw_smp_processor_id()
#endif
#define get_cpu() ({ preempt_disable(); smp_processor_id(); })