powerpc/64s: Use dec_mm_active_cpus helper

Avoid open-coded atomic_dec on mm->context.active_cpus and use the
function made for it. Add CONFIG_DEBUG_VM underflow checking on the
counter.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230524060821.148015-3-npiggin@gmail.com

diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h
index 570a496..5cf0e9c 100644 (file)
--- a/arch/powerpc/include/asm/book3s/64/mmu.h
+++ b/arch/powerpc/include/asm/book3s/64/mmu.h
@@ -261,7 +261,7 @@ static inline void radix_init_pseries(void) { }
 #define arch_clear_mm_cpumask_cpu(cpu, mm)                             \
        do {                                                            \
                if (cpumask_test_cpu(cpu, mm_cpumask(mm))) {            \
-                       atomic_dec(&(mm)->context.active_cpus);         \
+                       dec_mm_active_cpus(mm);                         \
                        cpumask_clear_cpu(cpu, mm_cpumask(mm));         \
                }                                                       \
        } while (0)

diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h
index 57f5017..37bffa0 100644 (file)
--- a/arch/powerpc/include/asm/mmu_context.h
+++ b/arch/powerpc/include/asm/mmu_context.h
@@ -127,6 +127,7 @@ static inline void inc_mm_active_cpus(struct mm_struct *mm)
 
 static inline void dec_mm_active_cpus(struct mm_struct *mm)
 {
+       VM_WARN_ON_ONCE(atomic_read(&mm->context.active_cpus) <= 0);
        atomic_dec(&mm->context.active_cpus);
 }
 

diff --git a/arch/powerpc/mm/book3s64/radix_tlb.c b/arch/powerpc/mm/book3s64/radix_tlb.c
index 0bd4866..4e72d80 100644 (file)
--- a/arch/powerpc/mm/book3s64/radix_tlb.c
+++ b/arch/powerpc/mm/book3s64/radix_tlb.c
@@ -820,7 +820,7 @@ void exit_lazy_flush_tlb(struct mm_struct *mm, bool always_flush)
         * that's what the caller expects.
         */
        if (cpumask_test_cpu(cpu, mm_cpumask(mm))) {
-               atomic_dec(&mm->context.active_cpus);
+               dec_mm_active_cpus(mm);
                cpumask_clear_cpu(cpu, mm_cpumask(mm));
                always_flush = true;
        }