[PATCH v2 03/15] riscv: misaligned: use on_each_cpu() for scalar misaligned access probing

[Clément Léger]

schedule_on_each_cpu() was used without any good reason while documented
as very slow. This call was in the boot path, so better use
on_each_cpu() for scalar misaligned checking. Vector misaligned check
still needs to use schedule_on_each_cpu() since it requires irqs to be
enabled but that's less of a problem since this code is ran in a kthread.
Add a comment to explicit that.

Signed-off-by: Clément Léger <cle...@rivosinc.com>
---
 arch/riscv/kernel/traps_misaligned.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/riscv/kernel/traps_misaligned.c 
b/arch/riscv/kernel/traps_misaligned.c
index 66eef398bad4..eb9157e3af73 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -616,6 +616,11 @@ bool check_vector_unaligned_access_emulated_all_cpus(void)
                return false;
        }
 
+       /*
+        * While being documented as very slow, schedule_on_each_cpu() is used
+        * since kernel_vector_begin() that is called inside the vector code
+        * expects irqs to be enabled or it will panic().
+        */
        schedule_on_each_cpu(check_vector_unaligned_access_emulated);
 
        for_each_online_cpu(cpu)
@@ -636,7 +641,7 @@ bool check_vector_unaligned_access_emulated_all_cpus(void)
 
 static bool unaligned_ctl __read_mostly;
 
-static void check_unaligned_access_emulated(struct work_struct *work 
__always_unused)
+static void check_unaligned_access_emulated(void *arg __always_unused)
 {
        int cpu = smp_processor_id();
        long *mas_ptr = per_cpu_ptr(&misaligned_access_speed, cpu);
@@ -677,7 +682,7 @@ bool check_unaligned_access_emulated_all_cpus(void)
         * accesses emulated since tasks requesting such control can run on any
         * CPU.
         */
-       schedule_on_each_cpu(check_unaligned_access_emulated);
+       on_each_cpu(check_unaligned_access_emulated, NULL, 1);
 
        for_each_online_cpu(cpu)
                if (per_cpu(misaligned_access_speed, cpu)
-- 
2.47.2