Re: [PATCH 05/16] staging/lustre: fix up obsolete cpu function usage.

[Rusty Russell <rusty@rustcorp.com.au>]

Oleg Drokin <green@linuxhacker.ru> writes:
> So there are 7 more users like this outside of Lustre in the kernel then, I'll try for a patch:

I can squash these if you want...

> ./drivers/scsi/hpsa.c:	for (i = 0; i < num_online_cpus(); i++) { -- this one seems to be just opencoding for_each_cpu, though

Yeah, that's easy to fix.

> ./arch/um/kernel/smp.c:	for (i = 0; i < num_online_cpus(); i++) { -- I wonder if UML is able to have discontiguous cpus up?
>
> ./arch/sh/include/asm/mmu_context.h:	for (i = 0; i < num_online_cpus(); i++) -- this seems to be the same bug we have.
>
> ./arch/sh/kernel/smp.c:		for (i = 0; i < num_online_cpus(); i++) -- this and the two below it too
> ./arch/sh/kernel/smp.c:		for (i = 0; i < num_online_cpus(); i++)
> ./arch/sh/kernel/smp.c:		for (i = 0; i < num_online_cpus(); i++)
>
> ./arch/m32r/kernel/smpboot.c:	for (cpu_id = 0 ; cpu_id < num_online_cpus() ; cpu_id++) -- this also is buggy, though it's just an info print.

These are arch code, and while they should be fixed (because people may
copy them), those archs probably don't support hotplug cpus.

Thanks!
Rusty.

Subject: Fix weird uses of num_online_cpus().

This may be OK in archs with contiguous CPU numbers and without
hotplug CPUs, but it sets a terrible example.

And open-coding it like drivers/scsi/hpsa.c is just weird.

BTRFS has a weird comparison with num_online_cpus() too, but since
BTRFS just screwed up my test machines' root partition, I'm not
touching it :)

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reported-by: Oleg Drokin <green@linuxhacker.ru>

diff --git a/arch/m32r/kernel/smpboot.c b/arch/m32r/kernel/smpboot.c
index bb21f4f63170..a468467542f4 100644
--- a/arch/m32r/kernel/smpboot.c
+++ b/arch/m32r/kernel/smpboot.c
@@ -376,7 +376,7 @@ void __init smp_cpus_done(unsigned int max_cpus)
 	if (!cpumask_equal(&cpu_callin_map, cpu_online_mask))
 		BUG();
 
-	for (cpu_id = 0 ; cpu_id < num_online_cpus() ; cpu_id++)
+	for_each_online_cpu(cpu_id)
 		show_cpu_info(cpu_id);
 
 	/*
diff --git a/arch/sh/include/asm/mmu_context.h b/arch/sh/include/asm/mmu_context.h
index b9d9489a5012..9f417feaf6e8 100644
--- a/arch/sh/include/asm/mmu_context.h
+++ b/arch/sh/include/asm/mmu_context.h
@@ -99,7 +99,7 @@ static inline int init_new_context(struct task_struct *tsk,
 {
 	int i;
 
-	for (i = 0; i < num_online_cpus(); i++)
+	for_each_online_cpu(i)
 		cpu_context(i, mm) = NO_CONTEXT;
 
 	return 0;
diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c
index fc5acfc93c92..de6be008fc01 100644
--- a/arch/sh/kernel/smp.c
+++ b/arch/sh/kernel/smp.c
@@ -363,7 +363,7 @@ void flush_tlb_mm(struct mm_struct *mm)
 		smp_call_function(flush_tlb_mm_ipi, (void *)mm, 1);
 	} else {
 		int i;
-		for (i = 0; i < num_online_cpus(); i++)
+		for_each_online_cpu(i)
 			if (smp_processor_id() != i)
 				cpu_context(i, mm) = 0;
 	}
@@ -400,7 +400,7 @@ void flush_tlb_range(struct vm_area_struct *vma,
 		smp_call_function(flush_tlb_range_ipi, (void *)&fd, 1);
 	} else {
 		int i;
-		for (i = 0; i < num_online_cpus(); i++)
+		for_each_online_cpu(i)
 			if (smp_processor_id() != i)
 				cpu_context(i, mm) = 0;
 	}
@@ -443,7 +443,7 @@ void flush_tlb_page(struct vm_area_struct *vma, unsigned long page)
 		smp_call_function(flush_tlb_page_ipi, (void *)&fd, 1);
 	} else {
 		int i;
-		for (i = 0; i < num_online_cpus(); i++)
+		for_each_online_cpu(i)
 			if (smp_processor_id() != i)
 				cpu_context(i, vma->vm_mm) = 0;
 	}
diff --git a/arch/um/kernel/smp.c b/arch/um/kernel/smp.c
index 74077892b34a..525c3657a6af 100644
--- a/arch/um/kernel/smp.c
+++ b/arch/um/kernel/smp.c
@@ -45,7 +45,7 @@ void smp_send_stop(void)
 	int i;
 
 	printk(KERN_INFO "Stopping all CPUs...");
-	for (i = 0; i < num_online_cpus(); i++) {
+	for_each_online_cpu(i) {
 		if (i == current_thread->cpu)
 			continue;
 		os_write_file(cpu_data[i].ipi_pipe[1], "S", 1);
diff --git a/drivers/scsi/hpsa.c b/drivers/scsi/hpsa.c
index a1cfbd3dda47..8eab107b53fb 100644
--- a/drivers/scsi/hpsa.c
+++ b/drivers/scsi/hpsa.c
@@ -6632,14 +6632,12 @@ static void fail_all_outstanding_cmds(struct ctlr_info *h)
 
 static void set_lockup_detected_for_all_cpus(struct ctlr_info *h, u32 value)
 {
-	int i, cpu;
+	int cpu;
 
-	cpu = cpumask_first(cpu_online_mask);
-	for (i = 0; i < num_online_cpus(); i++) {
+	for_each_online_cpu(cpu) {
 		u32 *lockup_detected;
 		lockup_detected = per_cpu_ptr(h->lockup_detected, cpu);
 		*lockup_detected = value;
-		cpu = cpumask_next(cpu, cpu_online_mask);
 	}
 	wmb(); /* be sure the per-cpu variables are out to memory */
 }