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Fri, 08 Aug 2025 21:07:19 -0700 (PDT) Message-ID: <0dadd6c5-3790-4887-a370-69cb7f0cc0b7@gmail.com> Date: Sat, 9 Aug 2025 12:07:13 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] watchdog: Don't need a definition of the perf fallback-attr To: peterz@infradead.org, linux-kernel@vger.kernel.org Cc: mingo@kernel.org, akpm@linux-foundation.org, song@kernel.org References: <20250727032516.10063-1-wangqing7171@gmail.com> From: Qing Wang In-Reply-To: <20250727032516.10063-1-wangqing7171@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hello, PING. Thanks, Qing. On 7/27/2025 11:25 AM, Qing Wong wrote: > From: Qing Wang > > The 'hardlockup_config_perf_event()' only overwrites the type and > config of the perf attr. It's wasteful that redefining a big static > variable to fallback. It’s just a matter of simply fallback these > two variables. > > Signed-off-by: Qing Wang > --- > kernel/watchdog_perf.c | 17 +++++++---------- > 1 file changed, 7 insertions(+), 10 deletions(-) > > diff --git a/kernel/watchdog_perf.c b/kernel/watchdog_perf.c > index 75af12ff774e..08b9acbd2aa4 100644 > --- a/kernel/watchdog_perf.c > +++ b/kernel/watchdog_perf.c > @@ -92,14 +92,6 @@ static struct perf_event_attr wd_hw_attr = { > .disabled = 1, > }; > > -static struct perf_event_attr fallback_wd_hw_attr = { > - .type = PERF_TYPE_HARDWARE, > - .config = PERF_COUNT_HW_CPU_CYCLES, > - .size = sizeof(struct perf_event_attr), > - .pinned = 1, > - .disabled = 1, > -}; > - > /* Callback function for perf event subsystem */ > static void watchdog_overflow_callback(struct perf_event *event, > struct perf_sample_data *data, > @@ -114,6 +106,12 @@ static void watchdog_overflow_callback(struct perf_event *event, > watchdog_hardlockup_check(smp_processor_id(), regs); > } > > +static void fallback_wd_hw_attr(void) > +{ > + wd_hw_attr.type = PERF_TYPE_HARDWARE; > + wd_hw_attr.config = PERF_COUNT_HW_CPU_CYCLES; > +} > + > static int hardlockup_detector_event_create(void) > { > unsigned int cpu; > @@ -133,8 +131,7 @@ static int hardlockup_detector_event_create(void) > evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL, > watchdog_overflow_callback, NULL); > if (IS_ERR(evt)) { > - wd_attr = &fallback_wd_hw_attr; > - wd_attr->sample_period = hw_nmi_get_sample_period(watchdog_thresh); > + fallback_wd_hw_attr(); > evt = perf_event_create_kernel_counter(wd_attr, cpu, NULL, > watchdog_overflow_callback, NULL); > }