linux-kernel - Re: [PATCH 2/2] RFC: soft/hardlookup: taint kernel

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Message-ID: <20190509092449.GA10828@jagdpanzerIV>
Date:   Thu, 9 May 2019 18:24:49 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Daniel Vetter <daniel.vetter@...ll.ch>
Cc:     Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Valdis Kletnieks <valdis.kletnieks@...edu>,
        Laurence Oberman <loberman@...hat.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        Don Zickus <dzickus@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Sinan Kaya <okaya@...nel.org>
Subject: Re: [PATCH 2/2] RFC: soft/hardlookup: taint kernel

On (05/02/19 21:42), Daniel Vetter wrote:
[..]
> @@ -469,6 +469,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
>  		add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
>  		if (softlockup_panic)
>  			panic("softlockup: hung tasks");
> +		else
> +			add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
>  		__this_cpu_write(soft_watchdog_warn, true);

Soft lockup sets TAINT_SOFTLOCKUP bit. Would it be enough for your CI?

[..]
> @@ -154,6 +154,8 @@ static void watchdog_overflow_callback(struct perf_event *event,
>
>  		if (hardlockup_panic)
>  			nmi_panic(regs, "Hard LOCKUP");
> +		else
> +			add_taint(TAINT_WARN, LOCKDEP_STILL_OK);

Maybe you can mirror what soft lockup does. Add a HARDLOCKUP taint bit

+++ b/include/linux/kernel.h
@@ -571,7 +571,8 @@ extern enum system_states {
 #define TAINT_LIVEPATCH                        15
 #define TAINT_AUX                      16
 #define TAINT_RANDSTRUCT               17
-#define TAINT_FLAGS_COUNT              18
+#define TAINT_HARDLOCKUP               18
+#define TAINT_FLAGS_COUNT              19

and then set TAINT_HARDLOCKUP in watchdog_overflow_callback().

Just a small idea, I'll leave this to more experienced people.

	-ss