On Wed, 22 Nov 2023 19:49:43 +0530 Naresh Kamboju naresh.kamboju@linaro.org wrote:

Hi Steven,

On Tue, 21 Nov 2023 at 02:06, Steven Rostedt rostedt@goodmis.org wrote:

...

On Thu, 16 Nov 2023 18:00:16 +0530 Naresh Kamboju naresh.kamboju@linaro.org wrote:

...

Following kernel crash noticed while running selftests: ftrace on arm64 Juno-r2 device running stable-rc linux-6.6.y kernel.

This kernel crash is hard to reproduce.

Can you test this patch.

I have applied your patch on top of Linux stable-rc linux-6.6.y and tested selftests: ftrace: for 100 iterations on arm64 Juno-r2 device.

Out of 100 test runs I see the following exception only once. I do not see crashes related to the previous report.

This one looks unrelated to the other crash.

Test log:

# ok 8 trace_pipe and trace_marker ... [ 282.726999] Unexpected kernel BRK exception at EL1

What's a "BRK exception"?

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