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Miller" , linux-perf-users@vger.kernel.org, Douglas Anderson Subject: [PATCH 02/10] watchdog/hardlockup: HAVE_NMI_WATCHDOG must implement watchdog_hardlockup_probe() Date: Fri, 26 May 2023 18:41:32 -0700 Message-ID: <20230526184139.2.Ic6ebbf307ca0efe91f08ce2c1eb4a037ba6b0700@changeid> X-Mailer: git-send-email 2.41.0.rc0.172.g3f132b7071-goog In-Reply-To: <20230527014153.2793931-1-dianders@chromium.org> References: <20230527014153.2793931-1-dianders@chromium.org> MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1767009764381963184?= X-GMAIL-MSGID: =?utf-8?q?1767009764381963184?= Right now there is one arch (sparc64) that selects HAVE_NMI_WATCHDOG without selecting HAVE_HARDLOCKUP_DETECTOR_ARCH. Because of that one architecture, we have some special case code in the watchdog core to handle the fact that watchdog_hardlockup_probe() isn't implemented. Let's implement watchdog_hardlockup_probe() for sparc64 and get rid of the special case. As a side effect of doing this, code inspection tells us that we could fix a minor bug where the system won't properly realize that NMI watchdogs are disabled. Specifically, on powerpc if CONFIG_PPC_WATCHDOG is turned off the arch might still select CONFIG_HAVE_HARDLOCKUP_DETECTOR_ARCH which selects CONFIG_HAVE_NMI_WATCHDOG. Since CONFIG_PPC_WATCHDOG was off then nothing will override the "weak" watchdog_hardlockup_probe() and we'll fallback to looking at CONFIG_HAVE_NMI_WATCHDOG. Suggested-by: Petr Mladek Signed-off-by: Douglas Anderson Reviewed-by: Petr Mladek --- Though this does fix a minor bug, I didn't mark this as "Fixes" because it's super minor. One could also argue that this wasn't a bug at all but simply was never an implemented feature. The code that added some amount of dynamicness here was commit a994a3147e4c ("watchdog/hardlockup/perf: Implement init time detection of perf") which, as per the title, was only intending to make "perf" dynamic. The old NMI watchdog presumably has never been handled dynamically. arch/Kconfig | 3 ++- arch/sparc/kernel/nmi.c | 5 +++++ kernel/watchdog.c | 13 ------------- 3 files changed, 7 insertions(+), 14 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 64d771855ecd..b4f6387b12fe 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -428,7 +428,8 @@ config HAVE_NMI_WATCHDOG bool help The arch provides a low level NMI watchdog. It provides - asm/nmi.h, and defines its own arch_touch_nmi_watchdog(). + asm/nmi.h, and defines its own watchdog_hardlockup_probe() and + arch_touch_nmi_watchdog(). config HAVE_HARDLOCKUP_DETECTOR_ARCH bool diff --git a/arch/sparc/kernel/nmi.c b/arch/sparc/kernel/nmi.c index 9d9e29b75c43..17cdfdbf1f3b 100644 --- a/arch/sparc/kernel/nmi.c +++ b/arch/sparc/kernel/nmi.c @@ -65,6 +65,11 @@ void arch_touch_nmi_watchdog(void) } EXPORT_SYMBOL(arch_touch_nmi_watchdog); +int __init watchdog_hardlockup_probe(void) +{ + return 0; +} + static void die_nmi(const char *str, struct pt_regs *regs, int do_panic) { int this_cpu = smp_processor_id(); diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 4b9e31edb47f..62230f5b8878 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -217,19 +217,6 @@ void __weak watchdog_hardlockup_disable(unsigned int cpu) { } */ int __weak __init watchdog_hardlockup_probe(void) { - /* - * If CONFIG_HAVE_NMI_WATCHDOG is defined then an architecture - * is assumed to have the hard watchdog available and we return 0. - */ - if (IS_ENABLED(CONFIG_HAVE_NMI_WATCHDOG)) - return 0; - - /* - * Hardlockup detectors other than those using CONFIG_HAVE_NMI_WATCHDOG - * are required to implement a non-weak version of this probe function - * to tell whether they are available. If they don't override then - * we'll return -ENODEV. - */ return -ENODEV; }