profile: setup_profiling_timer() is moslty not implemented

The setup_profiling_timer() is mostly un-implemented by many
architectures.  In many places it isn't guarded by CONFIG_PROFILE which is
needed for it to be used.  Make it a weak symbol in kernel/profile.c and
remove the 'return -EINVAL' implementations from the kenrel.

There are a couple of architectures which do return 0 from the
setup_profiling_timer() function but they don't seem to do anything else
with it.  To keep the /proc compatibility for now, leave these for a
future update or removal.

On ARM, this fixes the following sparse warning:
arch/arm/kernel/smp.c:793:5: warning: symbol 'setup_profiling_timer' was not declared. Should it be static?

Link: https://lkml.kernel.org/r/20220721195509.418205-1-ben-linux@fluff.org
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/alpha/kernel/smp.c

@@ -497,12 +497,6 @@ smp_cpus_done(unsigned int max_cpus)
 	       ((bogosum + 2500) / (5000/HZ)) % 100);
 }
 
-int
-setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 static void
 send_ipi_message(const struct cpumask *to_whom, enum ipi_message_type operation)
 {

arch/arc/kernel/smp.c

@@ -232,14 +232,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	return 0;
 }
 
-/*
- * not supported here
- */
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 /*****************************************************************************/
 /*              Inter Processor Interrupt Handling                           */
 /*****************************************************************************/

arch/arm/kernel/smp.c

@@ -787,14 +787,6 @@ void panic_smp_self_stop(void)
 		cpu_relax();
 }
 
-/*
- * not supported here
- */
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 #ifdef CONFIG_CPU_FREQ
 
 static DEFINE_PER_CPU(unsigned long, l_p_j_ref);

arch/arm64/kernel/smp.c

@@ -1078,14 +1078,6 @@ bool smp_crash_stop_failed(void)
 }
 #endif
 
-/*
- * not supported here
- */
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 static bool have_cpu_die(void)
 {
 #ifdef CONFIG_HOTPLUG_CPU

arch/csky/kernel/smp.c

@@ -243,11 +243,6 @@ void __init smp_cpus_done(unsigned int max_cpus)
 {
 }
 
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 void csky_start_secondary(void)
 {
 	struct mm_struct *mm = &init_mm;

arch/hexagon/kernel/smp.c

@@ -240,11 +240,6 @@ void arch_send_call_function_ipi_mask(const struct cpumask *mask)
 	send_ipi(mask, IPI_CALL_FUNC);
 }
 
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 void smp_start_cpus(void)
 {
 	int i;

arch/ia64/kernel/smp.c

@@ -333,9 +333,3 @@ smp_send_stop (void)
 {
 	send_IPI_allbutself(IPI_CPU_STOP);
 }
-
-int
-setup_profiling_timer (unsigned int multiplier)
-{
-	return -EINVAL;
-}

arch/openrisc/kernel/smp.c

@@ -197,12 +197,6 @@ void smp_send_stop(void)
 	smp_call_function(stop_this_cpu, NULL, 0);
 }
 
-/* not supported, yet */
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 void __init set_smp_cross_call(void (*fn)(const struct cpumask *, unsigned int))
 {
 	smp_cross_call = fn;

arch/parisc/kernel/smp.c

@@ -513,10 +513,3 @@ void __cpu_die(unsigned int cpu)
 
 	pdc_cpu_rendezvous_unlock();
 }
-
-#ifdef CONFIG_PROC_FS
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-#endif

arch/powerpc/kernel/smp.c

@@ -1674,13 +1674,6 @@ void start_secondary(void *unused)
 	BUG();
 }
 
-#ifdef CONFIG_PROFILING
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return 0;
-}
-#endif
-
 static void __init fixup_topology(void)
 {
 	int i;

arch/riscv/kernel/smp.c

@@ -64,12 +64,6 @@ bool arch_match_cpu_phys_id(int cpu, u64 phys_id)
 	return phys_id == cpuid_to_hartid_map(cpu);
 }
 
-/* Unsupported */
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 static void ipi_stop(void)
 {
 	set_cpu_online(smp_processor_id(), false);

arch/sparc/kernel/smp_32.c

@@ -174,11 +174,6 @@ void smp_call_function_interrupt(void)
 	irq_exit();
 }
 
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
 	int i, cpuid, extra;

arch/sparc/kernel/smp_64.c

@@ -1186,12 +1186,6 @@ void __irq_entry smp_penguin_jailcell(int irq, struct pt_regs *regs)
 	preempt_enable();
 }
 
-/* /proc/profile writes can call this, don't __init it please. */
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
 }

arch/x86/include/asm/apic.h

@@ -98,8 +98,6 @@ static inline bool apic_from_smp_config(void)
 #include <asm/paravirt.h>
 #endif
 
-extern int setup_profiling_timer(unsigned int);
-
 static inline void native_apic_mem_write(u32 reg, u32 v)
 {
 	volatile u32 *addr = (volatile u32 *)(APIC_BASE + reg);

arch/x86/kernel/apic/apic.c

@@ -1115,11 +1115,6 @@ DEFINE_IDTENTRY_SYSVEC(sysvec_apic_timer_interrupt)
 	set_irq_regs(old_regs);
 }
 
-int setup_profiling_timer(unsigned int multiplier)
-{
-	return -EINVAL;
-}
-
 /*
  * Local APIC start and shutdown
  */

kernel/profile.c

@@ -425,6 +425,12 @@ read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 	return read;
 }
 
+/* default is to not implement this call */
+int __weak setup_profiling_timer(unsigned mult)
+{
+	return -EINVAL;
+}
+
 /*
  * Writing to /proc/profile resets the counters
  *
@@ -435,8 +441,6 @@ static ssize_t write_profile(struct file *file, const char __user *buf,
 			     size_t count, loff_t *ppos)
 {
 #ifdef CONFIG_SMP
-	extern int setup_profiling_timer(unsigned int multiplier);
-
 	if (count == sizeof(int)) {
 		unsigned int multiplier;