On Mon, Mar 10, 2025 at 04:12:12PM +0100, Clément Léger wrote:
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 cleger@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 90ac74191357..ffac424faa88 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().
which expects
*/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
Reviewed-by: Andrew Jones ajones@ventanamicro.com