[PATCH v5 06/18] watchdog/hardlockup: Add comments to touch_nmi_watchdog()

Douglas Anderson
2023-05-19T17:21:29Z

In preparation for the buddy hardlockup detector, add comments to
touch_nmi_watchdog() to make it obvious that it touches the configured
hardlockup detector regardless of whether it's backed by an NMI. Also
note that arch_touch_nmi_watchdog() may not be architecture-specific.

Ideally, we'd like to rename these functions but that is a fairly
disruptive change touching a lot of drivers. After discussion [1] the
plan is to defer this until a good time.

[1] https://lore.kernel.org/r/ZFy0TX1tfhlH8gxj@alley

Signed-off-by: Douglas Anderson <dianders@chromium.org>
---

Changes in v5:
- No longer rename touch_nmi_watchdog(), just add comments.

Changes in v4:
- ("Rename touch_nmi_watchdog() to ...") new for v4.

include/linux/nmi.h | 23 +++++++++++++++++++----
1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/include/linux/nmi.h b/include/linux/nmi.h
index 454fe99c4874..fafab128f37e 100644
--- a/include/linux/nmi.h
+++ b/include/linux/nmi.h
@@ -125,15 +125,30 @@ void watchdog_nmi_disable(unsigned int cpu);
void lockup_detector_reconfigure(void);

/**
- * touch_nmi_watchdog - restart NMI watchdog timeout.
+ * touch_nmi_watchdog - manually pet the hardlockup watchdog.
*
- * If the architecture supports the NMI watchdog, touch_nmi_watchdog()
- * may be used to reset the timeout - for code which intentionally
- * disables interrupts for a long time. This call is stateless.
+ * If we support detecting hardlockups, touch_nmi_watchdog() may be
+ * used to pet the watchdog (reset the timeout) - for code which
+ * intentionally disables interrupts for a long time. This call is stateless.
+ *
+ * Though this function has "nmi" in the name, the hardlockup watchdog might
+ * not be backed by NMIs. This function will likely be renamed to
+ * touch_hardlockup_watchdog() in the future.
*/
static inline void touch_nmi_watchdog(void)
{
+ /*
+ * Pass on to the hardlockup detector selected via CONFIG_. Note that
+ * the hardlockup detector may not be arch-specific nor using NMIs
+ * and the arch_touch_nmi_watchdog() function will likely be renamed
+ * in the future.
+ */
arch_touch_nmi_watchdog();
+
+ /*
+ * Touching the hardlock detector implcitily pets the
+ * softlockup detector too
+ */
touch_softlockup_watchdog();
}

--
2.40.1.698.g37aff9b760-goog