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SubjectRe: WARNING: kernel/rcu/tree.c:618 rcu_eqs_enter.isra.67+0xd8
On Wed, Aug 12, 2020 at 09:43:35PM +0530, Naresh Kamboju wrote:
> While running kselftests bpf test_verifier on arm64 juno-r2 device
> the kernel BUG and WARNING noticed.
>
> metadata:
> git branch: linux-5.8.y
> git repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable-rc.git
> git commit: b30c8c9d42601af8ebeb3ad42085ff4134a111a0

I don't see this commit in -stable. Where should I be looking?

git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git

> git describe: v5.8-39-gb30c8c9d4260
> make_kernelversion: 5.8.1-rc1
> kernel-config:
> http://snapshots.linaro.org/openembedded/lkft/lkft/sumo/juno/lkft/linux-stable-rc-5.8/3/config
>
> [ 102.671323] bpf_prog_test_run_xdp+0xf4/0x1b0
> [ 102.675688] __do_sys_bpf+0x708/0x1d18
> [ 102.679442] __arm64_sys_bpf+0x28/0x38
> [ 102.683197] el0_svc_common.constprop.3+0x7c/0x198
> [ 102.687995] do_el0_svc+0x34/0xa0
> [ 102.691315] el0_sync_handler+0x16c/0x210
> [ 102.695329] el0_sync+0x140/0x180
> [ 102.698651] Code: d4202000 d4202000 d4202000 d4202000 (d4202000)
> [ 102.704758] ---[ end trace 14c3fdd625b93f51 ]---

Whatever error prompted this last stack trace needs attention.

> [ 102.709383] note: test_verifier[740] exited with preempt_count 2

Looks like there is a preempt_disable() that is lacking the
corresponding preempt_disable() on some code path.

Could you please try to bisect this?

> [ 102.715399] BUG: sleeping function called from invalid context at
> /usr/src/kernel/include/linux/percpu-rwsem.h:49
> [ 102.725680] in_atomic(): 0, irqs_disabled(): 128, non_block: 0,

As the "BUG:" message says...

> pid: 740, name: test_verifier
> [ 102.734219] INFO: lockdep is turned off.
> [ 102.738146] irq event stamp: 4369860
> [ 102.741729] hardirqs last enabled at (4369859):
> [<ffff80001015ab18>] ktime_get+0xc0/0x178
> [ 102.750010] hardirqs last disabled at (4369860):
> [<ffff800010029a04>] debug_exception_enter+0xac/0xe8
> [ 102.759249] softirqs last enabled at (4369842):
> [<ffff8000102161d4>] bpf_ksym_add+0x12c/0x148
> [ 102.767878] softirqs last disabled at (4369840):
> [<ffff8000102160d4>] bpf_ksym_add+0x2c/0x148
> [ 102.776419] CPU: 2 PID: 740 Comm: test_verifier Tainted: G D W
> 5.8.1-rc1 #1
> [ 102.784523] Hardware name: ARM Juno development board (r2) (DT)
> [ 102.790451] Call trace:
> [ 102.792900] dump_backtrace+0x0/0x1f8
> [ 102.796567] show_stack+0x2c/0x38
> [ 102.799889] dump_stack+0xf0/0x16c
> [ 102.803296] ___might_sleep+0x144/0x208
> [ 102.807137] __might_sleep+0x54/0x90
> [ 102.810719] exit_signals+0x54/0x3e8
> [ 102.814301] do_exit+0xc8/0xae0
> [ 102.817446] die+0x200/0x268
> [ 102.820329] arm64_notify_die+0xa0/0xc0
> [ 102.824172] do_debug_exception+0xf0/0x128
> [ 102.828275] el1_sync_handler+0x90/0xf0
> [ 102.832116] el1_sync+0x7c/0x100
> [ 102.835347] 0xffff8000000129b8
> [ 102.838493] bpf_prog_d53bb52e3f4483f9_F+0x38/0x8d0
> [ 102.843379] bpf_dispatcher_xdp_func+0x30/0x40
> [ 102.847830] bpf_test_run+0x180/0x570
> [ 102.851497] bpf_prog_test_run_xdp+0xf4/0x1b0
> [ 102.855861] __do_sys_bpf+0x708/0x1d18
> [ 102.859615] __arm64_sys_bpf+0x28/0x38
> [ 102.863369] el0_svc_common.constprop.3+0x7c/0x198
> [ 102.868167] do_el0_svc+0x34/0xa0
> [ 102.871486] el0_sync_handler+0x16c/0x210
> [ 102.875501] el0_sync+0x140/0x180
> [ 102.886823] ------------[ cut here ]------------
> [ 102.887376] kauditd_printk_skb: 125 callbacks suppressed
> [ 102.887387] audit: type=1701 audit(1597081698.472:1942):
> auid=4294967295 uid=0 gid=0 ses=4294967295 pid=738 comm=\"timeout\"
> exe=\"/usr/bin/timeout.coreutils\" sig=11 res=1
>
> [ 102.891463] WARNING: CPU: 2 PID: 0 at
> /usr/src/kernel/kernel/rcu/tree.c:618 rcu_eqs_enter.isra.67+0xd8/0xe0

If the line number matches -stable v5.8.1, this could be due
to exception-handler entry/exit updates of RCU state not being
set up properly. For example, if some system-call-like entry from
userspace failed to call rcu_user_exit() in a kernel built with context
tracking, though there are many ways to make this sort of error appear.
Historically, the most common cause has been a missing rcu_irq_enter()
or rcu_irq_exit() call one one of the exception paths.

It is of course quite possible that this error is a consequence of
earlier errors, so I would suggest focusing first on fixing the
earlier errors.

Thanx, Paul

> [ 102.891467] Modules linked in: rfkill tda998x cec drm_kms_helper
> drm crct10dif_ce fuse
> [ 102.891486] CPU: 2 PID: 0 Comm: swapper/2 Tainted: G D W
> 5.8.1-rc1 #1
> [ 102.891490] Hardware name: ARM Juno development board (r2) (DT)
> [ 102.891495] pstate: 200003c5 (nzCv DAIF -PAN -UAO BTYPE=--)
> [ 102.891501] pc : rcu_eqs_enter.isra.67+0xd8/0xe0
> [ 102.891511] lr : rcu_eqs_enter.isra.67+0x10/0xe0
> [ 102.957881] sp : ffff800013683f20
> [ 102.961198] x29: ffff800013683f20 x28: 0000000000000000
> [ 102.966519] x27: 0000000000000000 x26: ffff000973033800
> [ 102.971840] x25: ffff00097ef5fc80 x24: ffff800012651410
> [ 102.977162] x23: ffff800011f00c78 x22: ffff800012650000
> [ 102.982483] x21: ffff800012651000 x20: ffff800011f02000
> [ 102.987803] x19: ffff00097ef61ec0 x18: ffffffffffffffff
> [ 102.993124] x17: 0000000000000000 x16: 0000000000000000
> [ 102.998444] x15: 000000000000006c x14: 000000000000002a
> [ 103.003765] x13: 0000000000000002 x12: 0000000000000000
> [ 103.009086] x11: 0000000000000000 x10: ffff80001264b1c8
> [ 103.014406] x9 : 0000000000000000 x8 : ffff800012650a88
> [ 103.019727] x7 : ffff80001016d09c x6 : 0000000000000000
> [ 103.025048] x5 : 0000000000000000 x4 : 0000000000000000
> [ 103.030368] x3 : ffff800012650a88 x2 : 00000017f0129f00
> [ 103.035689] x1 : 4000000000000002 x0 : 4000000000000000
> [ 103.041011] Call trace:
> [ 103.043461] rcu_eqs_enter.isra.67+0xd8/0xe0
> [ 103.047739] rcu_idle_enter+0x44/0x70
> [ 103.051406] do_idle+0x214/0x2c0
> [ 103.054637] cpu_startup_entry+0x2c/0x70
> [ 103.058567] secondary_start_kernel+0x1a8/0x200
> [ 103.063103] irq event stamp: 449856
> [ 103.066599] hardirqs last enabled at (449855):
> [<ffff80001016d1ec>] tick_nohz_idle_exit+0x64/0xd0
> [ 103.075574] hardirqs last disabled at (449856):
> [<ffff800011329c08>] __schedule+0xf0/0x8f0
> [ 103.083853] softirqs last enabled at (449814):
> [<ffff8000100019bc>] __do_softirq+0x59c/0x5dc
> [ 103.092396] softirqs last disabled at (449803):
> [<ffff80001008fbf4>] irq_exit+0x144/0x150
>
>
> Full output log:
> https://qa-reports.linaro.org/lkft/linux-stable-rc-5.8-oe/build/v5.8-39-gb30c8c9d4260/testrun/3049360/suite/linux-log-parser/test/check-kernel-exception-1657446/log
>
> --
> Linaro LKFT
> https://lkft.linaro.org

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