Message-ID: <ZV-Q8e-gAwiO0oZF@FVFF77S0Q05N.cambridge.arm.com>
Date:   Thu, 23 Nov 2023 17:50:41 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
        mhiramat@...nel.org, lkft@...aro.org, lkft-triage@...ts.linaro.org
Subject: Re: selftests: ftrace: WARNING: __list_del_entry_valid_or_report
 (lib/list_debug.c:62 (discriminator 1))

On Wed, Nov 22, 2023 at 10:12:51AM -0500, Steven Rostedt wrote:
> On Wed, 22 Nov 2023 19:49:43 +0530
> Naresh Kamboju <naresh.kamboju@...aro.org> wrote:
> 
> > Hi Steven,
> > 
> > 
> > 
> > On Tue, 21 Nov 2023 at 02:06, Steven Rostedt <rostedt@...dmis.org> wrote:
> > >
> > > On Thu, 16 Nov 2023 18:00:16 +0530
> > > Naresh Kamboju <naresh.kamboju@...aro.org> wrote:
> > [  282.726999] Unexpected kernel BRK exception at EL1
> 
> What's a "BRK exception"?

That's triggered by a BRK instruction (software breakpoint), we use it like UD2
on x86.

> > [  282.731840] Internal error: BRK handler: 00000000f20003e8 [#1] PREEMPT SMP

That lump of hex here means "this was triggered by a BRK #1000" instruction.

That immediate (0x3e8 / 1000) is what GCC/Clang use for __builtin_trap(), which
is generated for a bunch of reasons, usually a sanitizer like UBSAN, or options
to trap on runtime issues.

Naresh, where can I find the config used for this run? I can try to reproduce
this and investigate.

Thanks,
Mark.

> > [  282.738752] Modules linked in: ftrace_direct ftrace_direct_too
> > hdlcd tda998x onboard_usb_hub drm_dma_helper cec crct10dif_ce
> > drm_kms_helper fuse drm backlight dm_mod ip_tables x_tables [last
> > unloaded: ftrace_direct]
> > [  282.758152] CPU: 0 PID: 987 Comm: rmmod Not tainted 6.6.2-rc1 #1
> 
> So this happened on removing a module? Unloading ftrace_direct?
> 
> This could be a direct trampoline bug.
> 
> But it doesn't look to be related to eventfs, so I'm going with my other patches.
> 
> Thanks,
> 
> -- Steve
> 
> 
> > [  282.764191] Hardware name: ARM Juno development board (r2) (DT)
> > [  282.770138] pstate: a00000c5 (NzCv daIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > [  282.777133] pc : ring_buffer_lock_reserve
> > (kernel/trace/ring_buffer.c:3304 (discriminator 1)
> > kernel/trace/ring_buffer.c:3819 (discriminator 1))
> > [  282.782230] lr : trace_function (kernel/trace/trace.c:992
> > kernel/trace/trace.c:3078)
> > [  282.786360] sp : ffff80008428ba20
> > [  282.789695] x29: ffff80008428ba20 x28: ffff00082bb367c0 x27: 0000000000000000
> > [  282.796898] x26: ffff800080371d84 x25: 0000000000000000 x24: ffff00097ed1e4b0
> > [  282.804100] x23: ffff000800018400 x22: 0000000000000000 x21: 0000000000000018
> > [  282.811302] x20: ffff000800018400 x19: ffff000800041400 x18: ffffffffffffffff
> > [  282.818504] x17: 0000000000000000 x16: 0000000000000000 x15: ffff800081d2ec58
> > [  282.825706] x14: ffffffffffffffff x13: ffff80008428beb0 x12: 000002550000ffff
> > [  282.832908] x11: ffff800083343078 x10: ffff80008428bbc0 x9 : ffff8000803e3110
> > [  282.840110] x8 : ffff80008428ba98 x7 : 0000000000000000 x6 : 0000000000000009
> > [  282.847311] x5 : 0000000000000081 x4 : fffffffffffffffb x3 : 0000000000000001
> > [  282.854513] x2 : ffffffffffffffff x1 : 0000000000000000 x0 : 0000000000000000
> > [  282.861715] Call trace:
> > [  282.864179] ring_buffer_lock_reserve
> > (kernel/trace/ring_buffer.c:3304 (discriminator 1)
> > kernel/trace/ring_buffer.c:3819 (discriminator 1))
> > [  282.868920] trace_function (kernel/trace/trace.c:992
> > kernel/trace/trace.c:3078)
> > [  282.872702] tracer_hardirqs_off (kernel/trace/trace_irqsoff.c:279
> > kernel/trace/trace_irqsoff.c:397 kernel/trace/trace_irqsoff.c:619
> > kernel/trace/trace_irqsoff.c:616)
> > [  282.877009] trace_hardirqs_off.part.0
> > (kernel/trace/trace_preemptirq.c:78 (discriminator 1))
> > [  282.881748] trace_hardirqs_off (kernel/trace/trace_preemptirq.c:94)
> > [  282.885791] obj_cgroup_charge (mm/memcontrol.c:3236 (discriminator
> > 1) mm/memcontrol.c:3364 (discriminator 1))
> > [  282.889918] kmem_cache_alloc (mm/slab.h:503 (discriminator 2)
> > mm/slab.h:714 (discriminator 2) mm/slub.c:3460 (discriminator 2)
> > mm/slub.c:3486 (discriminator 2) mm/slub.c:3493 (discriminator 2)
> > mm/slub.c:3502 (discriminator 2))
> > [  282.893873] __anon_vma_prepare (mm/rmap.c:197)
> > [  282.897999] __handle_mm_fault (mm/memory.c:4111 (discriminator 2)
> > mm/memory.c:3670 (discriminator 2) mm/memory.c:4981 (discriminator 2)
> > mm/memory.c:5122 (discriminator 2))
> > [  282.902213] handle_mm_fault (mm/memory.c:5287)
> > [  282.906077] do_page_fault (arch/arm64/mm/fault.c:513
> > arch/arm64/mm/fault.c:626)
> > [  282.909856] do_translation_fault (arch/arm64/mm/fault.c:714)
> > [  282.914068] do_mem_abort (arch/arm64/mm/fault.c:846 (discriminator 1))
> > [  282.917591] el0_da (arch/arm64/include/asm/daifflags.h:28
> > arch/arm64/kernel/entry-common.c:133
> > arch/arm64/kernel/entry-common.c:144
> > arch/arm64/kernel/entry-common.c:547)
> > [  282.920590] el0t_64_sync_handler (arch/arm64/kernel/entry-common.c:700)
> > [  282.924894] el0t_64_sync (arch/arm64/kernel/entry.S:595)
> > [ 282.928593] Code: 88037c22 35ffffa3 17fffff8 94549eb9 (d4207d00)
> > All code
> > ========
> >    0: 88037c22 stxr w3, w2, [x1]
> >    4: 35ffffa3 cbnz w3, 0xfffffffffffffff8
> >    8: 17fffff8 b 0xffffffffffffffe8
> >    c: 94549eb9 bl 0x1527af0
> >   10:* d4207d00 brk #0x3e8 <-- trapping instruction
> > 
> > Code starting with the faulting instruction
> > ===========================================
> >    0: d4207d00 brk #0x3e8
> > [  282.934716] ---[ end trace 0000000000000000 ]---
> > [  282.939358] note: rmmod[987] exited with irqs disabled
> > [  282.945441] note: rmmod[987] exited with preempt_count 2
> > [  282.951337] ------------[ cut here ]------------
> > [  282.955980] WARNING: CPU: 0 PID: 0 at kernel/context_tracking.c:128
> > ct_kernel_exit.constprop.0 (kernel/context_tracking.c:128
> > (discriminator 1))
> > [  282.965683] Modules linked in: ftrace_direct ftrace_direct_too
> > hdlcd tda998x onboard_usb_hub drm_dma_helper cec crct10dif_ce
> > drm_kms_helper fuse drm backlight dm_mod ip_tables x_tables [last
> > unloaded: ftrace_direct]
> > [  282.985075] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G      D
> >    6.6.2-rc1 #1
> > [  282.992767] Hardware name: ARM Juno development board (r2) (DT)
> > [  282.998713] pstate: 200003c5 (nzCv DAIF -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > [  283.005708] pc : ct_kernel_exit.constprop.0
> > (kernel/context_tracking.c:128 (discriminator 1))
> > [  283.010965] lr : ct_idle_enter (kernel/context_tracking.c:321)
> > [  283.014915] sp : ffff800083283b90
> > [  283.018249] x29: ffff800083283b90 x28: 00000000826a40ac x27: 0000000000000000
> > [  283.025452] x26: 00000000fef770dc x25: 0000000000000001 x24: ffff000822878880
> > [  283.032654] x23: 0000000000000001 x22: 00000000000003c0 x21: 0000000000010000
> > [  283.039856] x20: ffff80008172c118 x19: ffff00097ed16da0 x18: 0000000000000010
> > [  283.047059] x17: 0000000000000000 x16: 3030303030303020 x15: 0000000000000000
> > [  283.054260] x14: 0000000000000000 x13: 3220746e756f635f x12: 0000000000000003
> > [  283.061462] x11: ffff800083343078 x10: ffff800083283bc0 x9 : ffff800080039620
> > [  283.068665] x8 : ffff800083283af8 x7 : 0000000000000000 x6 : 000000000000003f
> > [  283.075867] x5 : 4000000000000002 x4 : ffff8008fc5b4000 x3 : ffff800083283b90
> > [  283.083069] x2 : ffff800082762da0 x1 : 4000000000000000 x0 : ffff800082762da0
> > [  283.090271] Call trace:
> > [  283.092736] ct_kernel_exit.constprop.0
> > (kernel/context_tracking.c:128 (discriminator 1))
> > [  283.097646] ct_idle_enter (kernel/context_tracking.c:321)
> > [  283.101249] cpu_suspend (arch/arm64/kernel/suspend.c:130)
> > [  283.104854] psci_cpu_suspend_enter (drivers/firmware/psci/psci.c:488)
> > [  283.109244] psci_enter_idle_state
> > (drivers/cpuidle/cpuidle-psci.c:190 (discriminator 10))
> > [  283.113544] cpuidle_enter_state (drivers/cpuidle/cpuidle.c:267)
> > [  283.117757] cpuidle_enter (drivers/cpuidle/cpuidle.c:390 (discriminator 2))
> > [  283.121361] do_idle (kernel/sched/idle.c:134
> > kernel/sched/idle.c:215 kernel/sched/idle.c:282)
> > [  283.124619] cpu_startup_entry (kernel/sched/idle.c:380 (discriminator 1))
> > [  283.128572] rest_init (include/linux/cpumask.h:1058 init/main.c:700)
> > [  283.131913] arch_call_rest_init+0x18/0x20
> > [  283.136042] start_kernel (init/main.c:882 (discriminator 1))
> > [  283.139734] __primary_switched (arch/arm64/kernel/head.S:524)
> > [  283.143775] ---[ end trace 0000000000000000 ]---
> > 
> > Links:
> > - https://lkft.validation.linaro.org/scheduler/job/7043802#L1756
> > 
> > --
> > Linaro LKFT
> > https://lkft.linaro.org
> > 
> > > Note, there's a similar bug on 6.7-rc1 which I'll fix first. And when
> > > that's accepted, I'll push this one for v6.6. This may be two patches as
> > > one if the d_invalidate() issue, and another is a memory leak fix.
> > >
> > > -- Steve
> > >
> > > diff --git a/fs/tracefs/event_inode.c b/fs/tracefs/event_inode.c
> > > index 5fcfb634fec2..b60048469df1 100644
> > > --- a/fs/tracefs/event_inode.c
> > > +++ b/fs/tracefs/event_inode.c
> > > @@ -289,6 +289,8 @@ void eventfs_set_ef_status_free(struct tracefs_inode *ti, struct dentry *dentry)
> > >                 ef = dentry->d_fsdata;
> > >                 if (ef)
> > >                         free_ef(ef);
> > > +               else
> > > +                       kfree(ei);
> > >                 return;
> > >         }
> > >
> > > @@ -342,7 +344,6 @@ static void eventfs_post_create_dir(struct eventfs_file *ef)
> > >  static struct dentry *
> > >  create_dentry(struct eventfs_file *ef, struct dentry *parent, bool lookup)
> > >  {
> > > -       bool invalidate = false;
> > >         struct dentry *dentry;
> > >
> > >         mutex_lock(&eventfs_mutex);
> > > @@ -387,23 +388,24 @@ create_dentry(struct eventfs_file *ef, struct dentry *parent, bool lookup)
> > >                         eventfs_post_create_dir(ef);
> > >                 dentry->d_fsdata = ef;
> > >         } else {
> > > -               /* A race here, should try again (unless freed) */
> > > -               invalidate = true;
> > > -
> > >                 /*
> > > +                * If we are here then the directory is being freed.
> > > +                * The simple_recursive_removal() will get rid of the dentry
> > > +                * here.
> > > +                */
> > > +               dentry = NULL;
> > > +                /*
> > >                  * Should never happen unless we get here due to being freed.
> > >                  * Otherwise it means two dentries exist with the same name.
> > >                  */
> > >                 WARN_ON_ONCE(!ef->is_freed);
> > >         }
> > >         mutex_unlock(&eventfs_mutex);
> > > -       if (invalidate)
> > > -               d_invalidate(dentry);
> > >
> > > -       if (lookup || invalidate)
> > > +       if (lookup)
> > >                 dput(dentry);
> > >
> > > -       return invalidate ? NULL : dentry;
> > > +       return dentry;
> > >  }
> > >
> > >  static bool match_event_file(struct eventfs_file *ef, const char *name)
> > > --
> > > 2.42.0
> > >  
> 

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