linux-kernel - Re: BUG: sleeping function called from invalid context at kernel/kallsyms.c:305

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Date:   Tue, 20 Dec 2022 09:54:45 +0100
From:   Anders Roxell <anders.roxell@...aro.org>
To:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
Cc:     mcgrof@...nel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: BUG: sleeping function called from invalid context at kernel/kallsyms.c:305

On Sat, 17 Dec 2022 at 04:29, Leizhen (ThunderTown)
<thunder.leizhen@...wei.com> wrote:
>
>
>
> On 2022/12/16 18:45, Anders Roxell wrote:
> > Hi,
> >
> > I'm building an arm64 allmodconfig kernel (see the .config [1]) on
> > yesterdays next tag 20221215 with KALLSYMS_SELFTEST enabled and I saw
> > the following bug when the selftest ran:
> >
> > [29725.015182][   T58] BUG: sleeping function called from invalid
> > context at kernel/kallsyms.c:305
> > [29725.022953][   T58] in_atomic(): 0, irqs_disabled(): 128,
> > non_block: 0, pid: 58, name: kallsyms_test
> > [29725.031272][   T58] preempt_count: 0, expected: 0
> > [29725.035903][   T58] RCU nest depth: 0, expected: 0
> > [29725.040574][   T58] no locks held by kallsyms_test/58.
> > [29725.045494][   T58] irq event stamp: 18899904
> > [29725.049809][ T58] hardirqs last enabled at (18899903):
> > finish_task_switch.isra.0 (core.c:?)
> > [29725.059608][ T58] hardirqs last disabled at (18899904):
> > test_perf_kallsyms_on_each_symbol (kallsyms_selftest.c:?)
> > [29725.069936][ T58] softirqs last enabled at (18899886): __do_softirq (??:?)
> > [29725.078670][ T58] softirqs last disabled at (18899879):
> > ____do_softirq (irq.c:?)
> > [29725.087399][   T58] CPU: 0 PID: 58 Comm: kallsyms_test Tainted: G
> >              T  6.1.0-next-20221215 #2
> > 0a142be8faea13ac333ed9a1cf4e71b6966ad16e
> > [29725.099607][   T58] Hardware name: linux,dummy-virt (DT)
> > [29725.104674][   T58] Call trace:
> > [29725.107909][ T58] dump_backtrace (??:?)
> > [29725.112706][ T58] show_stack (??:?)
> > [29725.116883][ T58] dump_stack_lvl (??:?)
> > [29725.121666][ T58] dump_stack (??:?)
> > [29725.125852][ T58] __might_resched (??:?)
> > [29725.130712][ T58] kallsyms_on_each_symbol (??:?)
> > [29725.136018][ T58] test_perf_kallsyms_on_each_symbol (kallsyms_selftest.c:?)
> > [29725.142008][ T58] test_entry (kallsyms_selftest.c:?)
> > [29725.146312][ T58] kthread (kthread.c:?)
> > [29725.150567][ T58] ret_from_fork (??:?)
> > [29734.975283][   T58] kallsyms_selftest: kallsyms_on_each_symbol()
> > traverse all: 5744310840 ns
> > [29734.992268][   T58] kallsyms_selftest:
> > kallsyms_on_each_match_symbol() traverse all: 1164580 ns
> > [29735.049679][   T58] kallsyms_selftest: finish
> >
> > looks like the issue is that test_perf_kallsyms_on_each_symbol() does
> > these function calls:
> >
> >        local_irq_save(flags);
> >        t0 = sched_clock();
> >        kallsyms_on_each_match_symbol(match_symbol, stat.name, &stat);
> >        t1 = sched_clock();
> >        local_irq_restore(flags);
> >
> > and inside kallsyms_on_each_match_symbol(), cond_resched() is called.
> >
> > Any ideas how to solve this?
>
> I was initially hoping that the test process would not be interrupted.
> It is not a big problem to remove local_irq_save(). From a probabilistic
> statistical point of view: it does not affect the horizontal comparison
> between kallsyms_on_each_symbol() and kallsyms_on_each_match_symbol(),
> and the vertical comparison before and after optimization is also not
> affected.
>
> Or do not call cond_resched() during the test. This method seems to be
> a little better.

I tried this patch and yes it made the kallsyms selftest to finish.

Please send a patch.

Cheers,
Anders

>
> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
> index e31b4d87a4e1b71..9e07fabaf08e647 100644
> --- a/kernel/kallsyms.c
> +++ b/kernel/kallsyms.c
> @@ -358,7 +358,8 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *,
>                 ret = fn(data, namebuf, NULL, kallsyms_sym_address(i));
>                 if (ret != 0)
>                         return ret;
> -               cond_resched();
> +               if (!IS_ENABLED(CONFIG_KALLSYMS_SELFTEST))
> +                       cond_resched();
>         }
>         return 0;
>  }
> @@ -375,7 +376,8 @@ int kallsyms_on_each_match_symbol(int (*fn)(void *, unsigned long),
>
>         for (i = start; !ret && i <= end; i++) {
>                 ret = fn(data, kallsyms_sym_address(get_symbol_seq(i)));
> -               cond_resched();
> +               if (!IS_ENABLED(CONFIG_KALLSYMS_SELFTEST))
> +                       cond_resched();
>         }
>
>         return ret;
>
> >
> > Cheers,
> > Anders
> > [1] https://people.linaro.org/~anders.roxell/next-20221215.config
> > .
> >
>
> --
> Regards,
>   Zhen Lei