linux-kernel - [PATCH v2] smp_call_function: use inline helpers instead of macros

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Date:   Wed, 26 Jul 2017 15:32:28 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Arnd Bergmann <arnd@...db.de>, Paolo Bonzini <pbonzini@...hat.com>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <james.hogan@...tec.com>,
        Paul Burton <paul.burton@...tec.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juergen Gross <jgross@...e.com>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2] smp_call_function: use inline helpers instead of macros

A new caller of smp_call_function() passes a local variable as the 'wait'
argument, and that variable is otherwise unused, so we get a warning
in non-SMP configurations:

virt/kvm/kvm_main.c: In function 'kvm_make_all_cpus_request':
virt/kvm/kvm_main.c:195:7: error: unused variable 'wait' [-Werror=unused-variable]
  bool wait = req & KVM_REQUEST_WAIT;

This addresses the warning by changing the two macros into inline functions.
As reported by the 0day build bot, a small change is required in the MIPS
r4k code for this, which then gets a warning about a missing variable.

Fixes: 7a97cec26b94 ("KVM: mark requests that need synchronization")
Cc: Paolo Bonzini <pbonzini@...hat.com>
Link: https://patchwork.kernel.org/patch/9722063/
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
v2: - fix MIPS build error reported by kbuild test robot
    - remove up_smp_call_function()
---
 arch/mips/mm/c-r4k.c |  2 ++
 include/linux/smp.h  | 12 +++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/mips/mm/c-r4k.c b/arch/mips/mm/c-r4k.c
index 81d6a15c93d0..f353bf5f24f1 100644
--- a/arch/mips/mm/c-r4k.c
+++ b/arch/mips/mm/c-r4k.c
@@ -97,9 +97,11 @@ static inline void r4k_on_each_cpu(unsigned int type,
 				   void (*func)(void *info), void *info)
 {
 	preempt_disable();
+#ifdef CONFIG_SMP
 	if (r4k_op_needs_ipi(type))
 		smp_call_function_many(&cpu_foreign_map[smp_processor_id()],
 				       func, info, 1);
+#endif
 	func(info);
 	preempt_enable();
 }
diff --git a/include/linux/smp.h b/include/linux/smp.h
index 68123c1fe549..ea24e2d3504c 100644
--- a/include/linux/smp.h
+++ b/include/linux/smp.h
@@ -135,17 +135,19 @@ static inline void smp_send_stop(void) { }
  *	These macros fold the SMP functionality into a single CPU system
  */
 #define raw_smp_processor_id()			0
-static inline int up_smp_call_function(smp_call_func_t func, void *info)
+static inline int smp_call_function(smp_call_func_t func, void *info, int wait)
 {
 	return 0;
 }
-#define smp_call_function(func, info, wait) \
-			(up_smp_call_function(func, info))
 
 static inline void smp_send_reschedule(int cpu) { }
 #define smp_prepare_boot_cpu()			do {} while (0)
-#define smp_call_function_many(mask, func, info, wait) \
-			(up_smp_call_function(func, info))
+
+static inline void smp_call_function_many(const struct cpumask *mask,
+			    smp_call_func_t func, void *info, bool wait)
+{
+}
+
 static inline void call_function_init(void) { }
 
 static inline int
-- 
2.9.0