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Thu, 13 Mar 2025 05:57:33 -0700 (PDT) Date: Thu, 13 Mar 2025 13:57:32 +0100 From: Andrew Jones To: =?utf-8?B?Q2zDqW1lbnQgTMOpZ2Vy?= Cc: Paul Walmsley , Palmer Dabbelt , Anup Patel , Atish Patra , Shuah Khan , Jonathan Corbet , linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-kselftest@vger.kernel.org, Samuel Holland Subject: Re: [PATCH v3 05/17] riscv: misaligned: use on_each_cpu() for scalar misaligned access probing Message-ID: <20250313-311b94f9bafe73bcd41158a1@orel> References: <20250310151229.2365992-1-cleger@rivosinc.com> <20250310151229.2365992-6-cleger@rivosinc.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250310151229.2365992-6-cleger@rivosinc.com> 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 > --- > 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