| Message ID | 20250310151229.2365992-6-cleger@rivosinc.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | riscv: add SBI FWFT misaligned exception delegation support | expand |
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 > + */ > 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 > Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
On 13/03/2025 13:57, Andrew Jones wrote: > 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() expects irqs to be enabled or it will panic(). > > which expects Hum that would yield the following: "schedule_on_each_cpu() is used since kernel_vector_begin() that is called inside the vector code 'which' expects irqs to be enabled or it will panic()." which seems wrong as well. I guess something like this would be better: "While being documented as very slow, schedule_on_each_cpu() is used since kernel_vector_begin() expects irqs to be enabled or it will panic()" Thanks, Clément > >> + */ >> 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 >> > > Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
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(). + */ 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)
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(-)