On Wed, Nov 22, 2023 at 10:12:51AM -0500, Steven Rostedt wrote:

On Wed, 22 Nov 2023 19:49:43 +0530
Naresh Kamboju [off-list ref] wrote:

quoted

Hi Steven,



On Tue, 21 Nov 2023 at 02:06, Steven Rostedt [off-list ref] wrote:

quoted

On Thu, 16 Nov 2023 18:00:16 +0530
Naresh Kamboju [off-list ref] 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.

quoted

[  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.

quoted

[  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

quoted

[  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

quoted

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