Hi Joel, Thanks for your quick fix.
Unfortunately, it fixes my original panic but introduces other issues(two wanings and one panic) on my arm64 vm, as below: -------------------------------------------------------------------- [ 3465.434942] ------------[ cut here ]------------ [ 3465.435481] refcount_t: addition on 0; use-after-free. [ 3465.437071] WARNING: CPU: 1 PID: 6708 at lib/refcount.c:25 refcount_warn_saturate+0x9c/0x140 [ 3465.437720] Modules linked in: preemptirq_delay_test(O-) sunrpc vfat fat ext4 mbcache jbd2 crct10dif_ce ghash_ce sha2_ce sha256_arm64 sha1_ce ip_tables xfs libcrc32c virtio_net net_failover failover virtio_mmio virtio_blk [ 3465.439787] CPU: 1 PID: 6708 Comm: rmmod Tainted: G O 5.6.0-rc7+ #18 [ 3465.440316] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 [ 3465.440967] pstate: 40000005 (nZcv daif -PAN -UAO) [ 3465.441297] pc : refcount_warn_saturate+0x9c/0x140 [ 3465.441592] lr : refcount_warn_saturate+0x9c/0x140 [ 3465.441919] sp : fffffe001382fd70 [ 3465.442160] x29: fffffe001382fd70 x28: fffffc004876d200 [ 3465.442649] x27: 0000000000000000 x26: 0000000000000000 [ 3465.443071] x25: 0000000000000000 x24: fffffe00115bbbf0 [ 3465.443670] x23: 0000000000000000 x22: 0000000000000200 [ 3465.444194] x21: fffffe0011273988 x20: fffffc0063fdd228 [ 3465.444576] x19: fffffc0063fdd200 x18: 0000000000000010 [ 3465.444939] x17: 0000000000000000 x16: 0000000000000000 [ 3465.445329] x15: ffffffffffffffff x14: fffffe0011273988 [ 3465.445698] x13: fffffe009382fa97 x12: fffffe001382fa9f [ 3465.446116] x11: fffffe00112b0000 x10: fffffe001382fa20 [ 3465.446498] x9 : 00000000ffffffd0 x8 : 6572662d72657466 [ 3465.446941] x7 : 0000000000000149 x6 : fffffe001127cf50 [ 3465.447375] x5 : fffffe001127c000 x4 : 0000000000000000 [ 3465.447757] x3 : fffffe001127cf50 x2 : 0000000000000000 [ 3465.448161] x1 : 2e36d2803fe6b700 x0 : 0000000000000000 [ 3465.448702] Call trace: [ 3465.448979] refcount_warn_saturate+0x9c/0x140 [ 3465.449330] kthread_stop+0x48/0x278 [ 3465.450144] preemptirq_delay_exit+0x28/0xfc8c [preemptirq_delay_test] [ 3465.450625] __arm64_sys_delete_module+0x14c/0x298 [ 3465.450998] do_el0_svc+0xf8/0x1e0 [ 3465.451372] el0_sync_handler+0x134/0x1bc [ 3465.451701] el0_sync+0x140/0x180 [ 3465.452099] ---[ end trace 1a8ec2201af5e8c7 ]--- [ 3465.478208] ------------[ cut here ]------------ [ 3465.478696] WARNING: CPU: 1 PID: 6708 at kernel/kthread.c:400 __kthread_bind_mask+0x34/0x90 [ 3465.479210] Modules linked in: preemptirq_delay_test(O-) sunrpc vfat fat ext4 mbcache jbd2 crct10dif_ce ghash_ce sha2_ce sha256_arm64 sha1_ce ip_tables xfs libcrc32c virtio_net net_failover failover virtio_mmio virtio_blk [ 3465.480509] CPU: 1 PID: 6708 Comm: rmmod Tainted: G W O 5.6.0-rc7+ #18 [ 3465.480966] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 [ 3465.481465] pstate: 40000005 (nZcv daif -PAN -UAO) [ 3465.481821] pc : __kthread_bind_mask+0x34/0x90 [ 3465.482129] lr : __kthread_bind_mask+0x30/0x90 [ 3465.482419] sp : fffffe001382fd30 [ 3465.482639] x29: fffffe001382fd30 x28: fffffc004876d200 [ 3465.483017] x27: 0000000000000000 x26: 0000000000000000 [ 3465.483385] x25: 0000000000000000 x24: fffffe00115bbbf0 [ 3465.483795] x23: 0000000000000000 x22: 0000000000000200 [ 3465.484251] x21: fffffe0010a9cb88 x20: 0000000000000040 [ 3465.484599] x19: fffffc0063fdd200 x18: 0000000000000010 [ 3465.484957] x17: 0000000000000000 x16: 0000000000000000 [ 3465.485347] x15: ffffffffffffffff x14: fffffe0011273988 [ 3465.485714] x13: fffffe009382fa97 x12: fffffe001382fa9f [ 3465.486210] x11: fffffe00112b0000 x10: fffffe001382fa20 [ 3465.486599] x9 : 00000000ffffffd0 x8 : 6572662d72657466 [ 3465.487039] x7 : 0000000000000149 x6 : fffffe001127cf50 [ 3465.487447] x5 : fffffe001127c000 x4 : 0000000000000001 [ 3465.487868] x3 : fffffe001127cf50 x2 : 2e36d2803fe6b700 [ 3465.488252] x1 : 0000000000000000 x0 : 0000000000000000 [ 3465.488628] Call trace: [ 3465.488851] __kthread_bind_mask+0x34/0x90 [ 3465.489192] kthread_unpark+0xa0/0xb0 [ 3465.489456] kthread_stop+0x8c/0x278 [ 3465.489736] preemptirq_delay_exit+0x28/0xfc8c [preemptirq_delay_test] [ 3465.490216] __arm64_sys_delete_module+0x14c/0x298 [ 3465.490594] do_el0_svc+0xf8/0x1e0 [ 3465.490850] el0_sync_handler+0x134/0x1bc [ 3465.491157] el0_sync+0x140/0x180 [ 3465.491413] ---[ end trace 1a8ec2201af5e8c8 ]--- [ 3465.504614] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 [ 3465.505340] Mem abort info: [ 3465.505553] ESR = 0x96000006 [ 3465.505855] EC = 0x25: DABT (current EL), IL = 32 bits [ 3465.506234] SET = 0, FnV = 0 [ 3465.506525] EA = 0, S1PTW = 0 [ 3465.506786] Data abort info: [ 3465.507037] ISV = 0, ISS = 0x00000006 [ 3465.507304] CM = 0, WnR = 0 [ 3465.507685] user pgtable: 64k pages, 42-bit VAs, pgdp=0000000082450000 [ 3465.508225] [0000000000000000] pgd=0000000000000000, pud=0000000000000000, pmd=0000000000000000 [ 3465.509049] Internal error: Oops: 96000006 [#1] PREEMPT SMP [ 3465.509527] Modules linked in: preemptirq_delay_test(O-) sunrpc vfat fat ext4 mbcache jbd2 crct10dif_ce ghash_ce sha2_ce sha256_arm64 sha1_ce ip_tables xfs libcrc32c virtio_net net_failover failover virtio_mmio virtio_blk [ 3465.510964] CPU: 1 PID: 6708 Comm: rmmod Tainted: G W O 5.6.0-rc7+ #18 [ 3465.511527] Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015 [ 3465.512031] pstate: 60000085 (nZCv daIf -PAN -UAO) [ 3465.512392] pc : __list_add_valid+0x18/0xa0 [ 3465.512740] lr : wait_for_completion+0xc8/0x178 [ 3465.513085] sp : fffffe001382fd00 [ 3465.513362] x29: fffffe001382fd00 x28: fffffc004876d200 [ 3465.513769] x27: 0000000000000000 x26: 0000000000000000 [ 3465.514205] x25: 0000000000000000 x24: fffffc0076e616c8 [ 3465.514638] x23: fffffe001382fd68 x22: 0000000000000000 [ 3465.515030] x21: fffffe0011273988 x20: fffffc0076e616c0 [ 3465.515444] x19: fffffc0076e616b8 x18: 0000000000000010 [ 3465.515826] x17: 0000000000000000 x16: 0000000000000000 [ 3465.516184] x15: ffffffffffffffff x14: fffffe0011273988 [ 3465.516584] x13: fffffe009382fa97 x12: fffffe001382fa9f [ 3465.516976] x11: fffffe00112b0000 x10: fffffe001382fa20 [ 3465.517351] x9 : 00000000ffffffd0 x8 : 6572662d72657466 [ 3465.517750] x7 : 0000000000000149 x6 : fffffe001127cf50 [ 3465.518169] x5 : 0000000000000001 x4 : fffffc0076e616c8 [ 3465.518454] x3 : fffffe0010128b38 x2 : 0000000000000000 [ 3465.518711] x1 : 0000000000000000 x0 : fffffe001382fd68 [ 3465.518985] Call trace: [ 3465.519157] __list_add_valid+0x18/0xa0 [ 3465.519351] wait_for_completion+0xc8/0x178 [ 3465.519578] kthread_stop+0x9c/0x278 [ 3465.519779] preemptirq_delay_exit+0x28/0xfc8c [preemptirq_delay_test] [ 3465.520109] __arm64_sys_delete_module+0x14c/0x298 [ 3465.520342] do_el0_svc+0xf8/0x1e0 [ 3465.520520] el0_sync_handler+0x134/0x1bc [ 3465.520718] el0_sync+0x140/0x180 [ 3465.521177] Code: 910003fd f9400442 eb01005f 54000141 (f9400041) [ 3465.522258] ---[ end trace 1a8ec2201af5e8c9 ]--- [ 3465.522746] Kernel panic - not syncing: Fatal exception [ 3465.523242] SMP: stopping secondary CPUs [ 3465.523898] Kernel Offset: disabled [ 3465.524423] CPU features: 0x10002,20006082 [ 3465.524939] Memory Limit: none [ 3465.525534] ---[ end Kernel panic - not syncing: Fatal exception ]--- -------------------------------------------------------------------- I am looking into these issues. Thanks, Xiao Yang On 2020/4/25 6:36, Joel Fernandes (Google) wrote: > Kthread running the test needs to be stopped or it can continue > executing code unloaded by module causing a crash. > > Suggested-by: Steven Rostedt<rost...@goodmis.org> > Reported-by: Xiao Yang<yangx...@cn.fujitsu.com> > Link: http://lore.kernel.org/r/5ea2b0c8.2080...@cn.fujitsu.com > Signed-off-by: Joel Fernandes (Google)<j...@joelfernandes.org> > --- > kernel/trace/preemptirq_delay_test.c | 5 ++++- > 1 file changed, 4 insertions(+), 1 deletion(-) > > diff --git a/kernel/trace/preemptirq_delay_test.c > b/kernel/trace/preemptirq_delay_test.c > index 31c0fad4cb9e1..1c28ca20e30b6 100644 > --- a/kernel/trace/preemptirq_delay_test.c > +++ b/kernel/trace/preemptirq_delay_test.c > @@ -145,10 +145,10 @@ static struct attribute_group attr_group = { > }; > > static struct kobject *preemptirq_delay_kobj; > +static struct task_struct *test_task; > > static int __init preemptirq_delay_init(void) > { > - struct task_struct *test_task; > int retval; > > test_task = preemptirq_start_test(); > @@ -171,6 +171,9 @@ static int __init preemptirq_delay_init(void) > static void __exit preemptirq_delay_exit(void) > { > kobject_put(preemptirq_delay_kobj); > + > + if (test_task) > + kthread_stop(test_task); > } > > module_init(preemptirq_delay_init)
