[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>

19 files changed, 41 insertions, 48 deletions

diff --git a/include/asm-alpha/smp.h b/include/asm-alpha/smp.h
index cbc173a..9950706 100644
--- a/include/asm-alpha/smp.h
+++ b/include/asm-alpha/smp.h
@@ -43,7 +43,7 @@ extern struct cpuinfo_alpha cpu_data[NR_CPUS];
 #define PROC_CHANGE_PENALTY     20
 
 #define hard_smp_processor_id()	__hard_smp_processor_id()
-#define smp_processor_id()	(current_thread_info()->cpu)
+#define raw_smp_processor_id()	(current_thread_info()->cpu)
 
 extern cpumask_t cpu_present_mask;
 extern cpumask_t cpu_online_map;
diff --git a/include/asm-arm/smp.h b/include/asm-arm/smp.h
index bd44f89..6c6c60a 100644
--- a/include/asm-arm/smp.h
+++ b/include/asm-arm/smp.h
@@ -21,7 +21,7 @@
 # error "<asm-arm/smp.h> included in non-SMP build"
 #endif
 
-#define smp_processor_id()	(current_thread_info()->cpu)
+#define raw_smp_processor_id() (current_thread_info()->cpu)
 
 extern cpumask_t cpu_present_mask;
 #define cpu_possible_map cpu_present_mask
diff --git a/include/asm-i386/smp.h b/include/asm-i386/smp.h
index e03a206..55ef31f 100644
--- a/include/asm-i386/smp.h
+++ b/include/asm-i386/smp.h
@@ -51,7 +51,7 @@ extern u8 x86_cpu_to_apicid[];
  * from the initial startup. We map APIC_BASE very early in page_setup(),
  * so this is correct in the x86 case.
  */
-#define __smp_processor_id() (current_thread_info()->cpu)
+#define raw_smp_processor_id() (current_thread_info()->cpu)
 
 extern cpumask_t cpu_callout_map;
 extern cpumask_t cpu_callin_map;
diff --git a/include/asm-ia64/smp.h b/include/asm-ia64/smp.h
index 3ba1a06..a391435 100644
--- a/include/asm-ia64/smp.h
+++ b/include/asm-ia64/smp.h
@@ -46,7 +46,7 @@ ia64_get_lid (void)
 #define SMP_IRQ_REDIRECTION	(1 << 0)
 #define SMP_IPI_REDIRECTION	(1 << 1)
 
-#define smp_processor_id()	(current_thread_info()->cpu)
+#define raw_smp_processor_id() (current_thread_info()->cpu)
 
 extern struct smp_boot_data {
 	int cpu_count;
diff --git a/include/asm-m32r/smp.h b/include/asm-m32r/smp.h
index 8cd4d0d..b9a20cd 100644
--- a/include/asm-m32r/smp.h
+++ b/include/asm-m32r/smp.h
@@ -66,7 +66,7 @@ extern volatile int cpu_2_physid[NR_CPUS];
 #define physid_to_cpu(physid)	physid_2_cpu[physid]
 #define cpu_to_physid(cpu_id)	cpu_2_physid[cpu_id]
 
-#define smp_processor_id()	(current_thread_info()->cpu)
+#define raw_smp_processor_id()	(current_thread_info()->cpu)
 
 extern cpumask_t cpu_callout_map;
 #define cpu_possible_map cpu_callout_map
diff --git a/include/asm-mips/smp.h b/include/asm-mips/smp.h
index 8ba370e..5618f1e 100644
--- a/include/asm-mips/smp.h
+++ b/include/asm-mips/smp.h
@@ -21,7 +21,7 @@
 #include <linux/cpumask.h>
 #include <asm/atomic.h>
 
-#define smp_processor_id()	(current_thread_info()->cpu)
+#define raw_smp_processor_id() (current_thread_info()->cpu)
 
 /* Map from cpu id to sequential logical cpu number.  This will only
    not be idempotent when cpus failed to come on-line.  */
diff --git a/include/asm-parisc/smp.h b/include/asm-parisc/smp.h
index fde77ac..9413f67 100644
--- a/include/asm-parisc/smp.h
+++ b/include/asm-parisc/smp.h
@@ -51,7 +51,7 @@ extern void smp_send_reschedule(int cpu);
 
 extern unsigned long cpu_present_mask;
 
-#define smp_processor_id()	(current_thread_info()->cpu)
+#define raw_smp_processor_id()	(current_thread_info()->cpu)
 
 #endif /* CONFIG_SMP */
 
diff --git a/include/asm-ppc/smp.h b/include/asm-ppc/smp.h
index ebfb614..17530c2 100644
--- a/include/asm-ppc/smp.h
+++ b/include/asm-ppc/smp.h
@@ -44,7 +44,7 @@ extern void smp_message_recv(int, struct pt_regs *);
 #define NO_PROC_ID		0xFF            /* No processor magic marker */
 #define PROC_CHANGE_PENALTY	20
 
-#define smp_processor_id() (current_thread_info()->cpu)
+#define raw_smp_processor_id()	(current_thread_info()->cpu)
 
 extern int __cpu_up(unsigned int cpu);
 
diff --git a/include/asm-ppc64/smp.h b/include/asm-ppc64/smp.h
index c8646fa..8115ecb 100644
--- a/include/asm-ppc64/smp.h
+++ b/include/asm-ppc64/smp.h
@@ -45,7 +45,7 @@ void generic_cpu_die(unsigned int cpu);
 void generic_mach_cpu_die(void);
 #endif
 
-#define __smp_processor_id() (get_paca()->paca_index)
+#define raw_smp_processor_id()	(get_paca()->paca_index)
 #define hard_smp_processor_id() (get_paca()->hw_cpu_id)
 
 extern cpumask_t cpu_sibling_map[NR_CPUS];
diff --git a/include/asm-s390/smp.h b/include/asm-s390/smp.h
index 9473786..dd50e57 100644
--- a/include/asm-s390/smp.h
+++ b/include/asm-s390/smp.h
@@ -47,7 +47,7 @@ extern int smp_call_function_on(void (*func) (void *info), void *info,
  
 #define PROC_CHANGE_PENALTY	20		/* Schedule penalty */
 
-#define smp_processor_id() (S390_lowcore.cpu_data.cpu_nr)
+#define raw_smp_processor_id()	(S390_lowcore.cpu_data.cpu_nr)
 
 extern int smp_get_cpu(cpumask_t cpu_map);
 extern void smp_put_cpu(int cpu);
diff --git a/include/asm-sh/smp.h b/include/asm-sh/smp.h
index 38b5446..f19a8b3 100644
--- a/include/asm-sh/smp.h
+++ b/include/asm-sh/smp.h
@@ -25,7 +25,7 @@ extern cpumask_t cpu_possible_map;
 
 #define cpu_online(cpu)		cpu_isset(cpu, cpu_online_map)
 
-#define smp_processor_id()	(current_thread_info()->cpu)
+#define raw_smp_processor_id()	(current_thread_info()->cpu)
 
 /* I've no idea what the real meaning of this is */
 #define PROC_CHANGE_PENALTY	20
diff --git a/include/asm-sparc/smp.h b/include/asm-sparc/smp.h
index f986c0d..4f96d83 100644
--- a/include/asm-sparc/smp.h
+++ b/include/asm-sparc/smp.h
@@ -148,7 +148,7 @@ extern __inline__ int hard_smp_processor_id(void)
 }
 #endif
 
-#define smp_processor_id()	(current_thread_info()->cpu)
+#define raw_smp_processor_id()		(current_thread_info()->cpu)
 
 #define prof_multiplier(__cpu)		cpu_data(__cpu).multiplier
 #define prof_counter(__cpu)		cpu_data(__cpu).counter
diff --git a/include/asm-sparc64/smp.h b/include/asm-sparc64/smp.h
index 5e3e06d..110a2de 100644
--- a/include/asm-sparc64/smp.h
+++ b/include/asm-sparc64/smp.h
@@ -64,7 +64,7 @@ static __inline__ int hard_smp_processor_id(void)
 	}
 }
 
-#define smp_processor_id() (current_thread_info()->cpu)
+#define raw_smp_processor_id() (current_thread_info()->cpu)
 
 #endif /* !(__ASSEMBLY__) */
 
diff --git a/include/asm-um/smp.h b/include/asm-um/smp.h
index 4412d5d..d879eba 100644
--- a/include/asm-um/smp.h
+++ b/include/asm-um/smp.h
@@ -8,7 +8,8 @@
 #include "asm/current.h"
 #include "linux/cpumask.h"
 
-#define smp_processor_id() (current_thread->cpu)
+#define raw_smp_processor_id() (current_thread->cpu)
+
 #define cpu_logical_map(n) (n)
 #define cpu_number_map(n) (n)
 #define PROC_CHANGE_PENALTY	15 /* Pick a number, any number */
diff --git a/include/asm-x86_64/smp.h b/include/asm-x86_64/smp.h
index 96844fe..a7425aa 100644
--- a/include/asm-x86_64/smp.h
+++ b/include/asm-x86_64/smp.h
@@ -68,7 +68,7 @@ static inline int num_booting_cpus(void)
 	return cpus_weight(cpu_callout_map);
 }
 
-#define __smp_processor_id() read_pda(cpunumber)
+#define raw_smp_processor_id() read_pda(cpunumber)
 
 extern __inline int hard_smp_processor_id(void)
 {
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index e530c6c..beacd93 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -381,7 +381,7 @@ int lowmem_reserve_ratio_sysctl_handler(struct ctl_table *, int, struct file *,
 
 #include <linux/topology.h>
 /* Returns the number of the current Node. */
-#define numa_node_id()		(cpu_to_node(_smp_processor_id()))
+#define numa_node_id()		(cpu_to_node(raw_smp_processor_id()))
 
 #ifndef CONFIG_DISCONTIGMEM
 
diff --git a/include/linux/smp.h b/include/linux/smp.h
index dcf1db3..9dfa3ee 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(); })
diff --git a/include/net/route.h b/include/net/route.h
index d34ca8f..c3cd069 100644
--- a/include/net/route.h
+++ b/include/net/route.h
@@ -107,7 +107,7 @@ struct rt_cache_stat
 
 extern struct rt_cache_stat *rt_cache_stat;
 #define RT_CACHE_STAT_INC(field)					  \
-		(per_cpu_ptr(rt_cache_stat, _smp_processor_id())->field++)
+		(per_cpu_ptr(rt_cache_stat, raw_smp_processor_id())->field++)
 
 extern struct ip_rt_acct *ip_rt_acct;
 
diff --git a/include/net/snmp.h b/include/net/snmp.h
index a15ab25..a36bed8 100644
--- a/include/net/snmp.h
+++ b/include/net/snmp.h
@@ -128,18 +128,18 @@ struct linux_mib {
 #define SNMP_STAT_USRPTR(name)	(name[1])
 
 #define SNMP_INC_STATS_BH(mib, field) 	\
-	(per_cpu_ptr(mib[0], _smp_processor_id())->mibs[field]++)
+	(per_cpu_ptr(mib[0], raw_smp_processor_id())->mibs[field]++)
 #define SNMP_INC_STATS_OFFSET_BH(mib, field, offset)	\
-	(per_cpu_ptr(mib[0], _smp_processor_id())->mibs[field + (offset)]++)
+	(per_cpu_ptr(mib[0], raw_smp_processor_id())->mibs[field + (offset)]++)
 #define SNMP_INC_STATS_USER(mib, field) \
-	(per_cpu_ptr(mib[1], _smp_processor_id())->mibs[field]++)
+	(per_cpu_ptr(mib[1], raw_smp_processor_id())->mibs[field]++)
 #define SNMP_INC_STATS(mib, field) 	\
-	(per_cpu_ptr(mib[!in_softirq()], _smp_processor_id())->mibs[field]++)
+	(per_cpu_ptr(mib[!in_softirq()], raw_smp_processor_id())->mibs[field]++)
 #define SNMP_DEC_STATS(mib, field) 	\
-	(per_cpu_ptr(mib[!in_softirq()], _smp_processor_id())->mibs[field]--)
+	(per_cpu_ptr(mib[!in_softirq()], raw_smp_processor_id())->mibs[field]--)
 #define SNMP_ADD_STATS_BH(mib, field, addend) 	\
-	(per_cpu_ptr(mib[0], _smp_processor_id())->mibs[field] += addend)
+	(per_cpu_ptr(mib[0], raw_smp_processor_id())->mibs[field] += addend)
 #define SNMP_ADD_STATS_USER(mib, field, addend) 	\
-	(per_cpu_ptr(mib[1], _smp_processor_id())->mibs[field] += addend)
+	(per_cpu_ptr(mib[1], raw_smp_processor_id())->mibs[field] += addend)
 
 #endif