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From:   "Zhang, Qiang1" <qiang1.zhang@intel.com>
To:     "Zhang, Qiang1" <qiang1.zhang@intel.com>,
        "paulmck@kernel.org" <paulmck@kernel.org>
CC:     "frederic@kernel.org" <frederic@kernel.org>,
        "quic_neeraju@quicinc.com" <quic_neeraju@quicinc.com>,
        "rcu@vger.kernel.org" <rcu@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH v2] rcu: Make tiny RCU support leak callbacks for
 debug-object errors
Thread-Topic: [PATCH v2] rcu: Make tiny RCU support leak callbacks for
 debug-object errors
Thread-Index: AQHYjPSNkw8Leg1ATEaQzvaLUuKjoa1wEumAgACIyGCAACGEAIAAA9hQgAACRJA=
Date:   Wed, 6 Jul 2022 04:24:03 +0000
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On Wed, Jul 06, 2022 at 02:00:51AM +0000, Zhang, Qiang1 wrote:
> On Fri, Jul 01, 2022 at 10:44:04AM +0800, Zqiang wrote:
> > Currently, only tree RCU support leak callbacks setting when do
> > duplicate call_rcu(). this commit add leak callbacks setting when
> > fo duplicate call_rcu() for tiny RCU.
> >=20
> > Signed-off-by: Zqiang <qiang1.zhang@intel.com>
>=20
> >This does look plausible, thank you!
> >
> >What testing have you done?
> >
> >One important test for Tiny RCU is that the size of the kernel not
> >grow without a very good reason.  In this case, the added code should
> >be dead code in a production build (CONFIG_DEBUG_OBJECTS_RCU_HEAD=3Dn),
> >but it is good to check.
> >
> >It is of course also good to check that the messages print as expected,
> >which is what rcutorture.object_debug is there to help with.
>=20
> In the condition that the CONFIG_DEBUG_OBJECTS_RCU_HEAD=3Dn, the function=
 directly returns zero.
>=20
> #else   /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
> static inline int debug_rcu_head_queue(struct rcu_head *head)
> {
>         return 0;
> }
>
>Yes, like I said, the added code -should- be dead code.  But there is
>often a gap between "should" and "is", for example, compilers don't
>always do what we would like them to.  So please use the "size vmlinux"
>command with and without your patch for a kernel built (both times)
>with CONFIG_TINY_RCU=3Dy and CONFIG_DEBUG_OBJECTS_RCU_HEAD=3D=3Dn.
>
>The rest of the test results look good, thank you!

Hi Paul

1. CONFIG_TINY_RCU=3Dy and CONFIG_DEBUG_OBJECTS_RCU_HEAD=3Dy

Original:
text                      data                   bss                   dec =
                    hex       filename
26291319        20160143        15212544        61664006        3aceb06    =
vmlinux

Applay patch:
text                       data                  bss                     de=
c                 hex    filename
26291319        20160431        15212544        61664294        3acec26 vml=
inux

2. CONFIG_TINY_RCU=3Dy and CONFIG_DEBUG_OBJECTS_RCU_HEAD=3Dn

Original:
text                    data                   bss                         =
 dec     hex filename
26290663        20159823        15212544        61663030        3ace736 vml=
inux

Applay patch:
text                     data                     bss                    de=
c     hex filename
26290663        20159823        15212544        61663030        3ace736 vml=
inux

Thanks
Zqiang

>
>							Thanx, Paul
>
> My test results are as follows:
>=20
> runqemu kvm slirp nographic qemuparams=3D"-m 2048 -smp 1" bootparams=3D"r=
cutorture.object_debug=3D1" -d
>=20
> log:
> root@qemux86-64:/# zcat /proc/config.gz | grep RCU
> # RCU Subsystem
> CONFIG_TINY_RCU=3Dy
> CONFIG_DEBUG_OBJECTS_RCU_HEAD=3Dy
>=20
> [    1.015657] rcutorture: WARN: Duplicate call_rcu() test starting.
> [    1.015659] ------------[ cut here ]------------
> [    1.015659] ODEBUG: activate active (active state 1) object type: rcu_=
head hint: 0x0
> [    1.015680] WARNING: CPU: 0 PID: 1 at lib/debugobjects.c:502 debug_pri=
nt_object+0xda/0x100
> [    1.016329] Modules linked in:
> [    1.016329] CPU: 0 PID: 1 Comm: swapper Not tainted 5.19.0-rc3-yoctode=
v-standard+ #214
> [    1.016329] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS r=
el-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> [    1.016329] RIP: 0010:debug_print_object+0xda/0x100
> [    1.016329] Code: 60 ec 45 92 e8 a7 7b a0 ff 4d 89 f9 4d 89 e8 44 89 e=
1 48 8b 14 dd 60 ec 45 92 4c 89 f6 48 c7 c7 e0 e1 45 92 e8 f9 d1 b3 00 90 <=
0f> e
> [    1.016329] RSP: 0000:ffff888001337be0 EFLAGS: 00010086
> [    1.016329] RAX: 0000000000000000 RBX: 0000000000000003 RCX: 000000000=
0000000
> [    1.016329] RDX: 00000000ffffffd8 RSI: 0000000000000004 RDI: ffffed100=
0266f6e
> [    1.016329] RBP: ffff888001337c10 R08: ffffffff90a56ee6 R09: fffffbfff=
25df5c2
> [    1.016329] R10: ffffffff92efae0b R11: fffffbfff25df5c1 R12: 000000000=
0000001
> [    1.016329] R13: ffffffff9227f520 R14: ffffffff9245e8a0 R15: 000000000=
0000000
> [    1.016329] FS:  0000000000000000(0000) GS:ffffffff92cbb000(0000) knlG=
S:0000000000000000
> [    1.016329] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    1.016329] CR2: ffff888017401000 CR3: 0000000015a3c000 CR4: 000000000=
01506f0
> [    1.016329] Call Trace:
> [    1.016329]  <TASK>
> [    1.016329]  debug_object_activate+0x2b9/0x300
> [    1.016329]  ? debug_object_assert_init+0x220/0x220
> [    1.016329]  ? lockdep_hardirqs_on_prepare+0x13/0x210
> [    1.016329]  ? call_rcu+0xde/0x150
> [    1.016329]  ? trace_hardirqs_on+0x54/0x120
> [    1.016329]  ? rcu_torture_fwd_cb_hist.cold+0xe9/0xe9
> [    1.016329]  call_rcu+0x20/0x150
> [    1.016329]  rcu_torture_init+0x1687/0x1759
> [    1.016329]  ? srcu_init+0xaa/0xaa
> [    1.016329]  ? irq_debugfs_copy_devname+0x70/0x70
> [    1.016329]  ? rcu_torture_barrier1cb+0x40/0x40
> [    1.016329]  ? rcu_torture_barrier1cb+0x40/0x40
> [    1.016329]  ? irq_pm_init_ops+0x19/0x19
> [    1.016329]  ? mutex_unlock+0x12/0x20
> [    1.016329]  ? srcu_init+0xaa/0xaa
> [    1.016329]  do_one_initcall+0xc1/0x310
> [    1.016329]  ? initcall_blacklisted+0x140/0x140
> [    1.016329]  ? parameq+0x20/0x90
> [    1.016329]  ? __kmalloc+0x238/0x5d0
> [    1.016329]  ? rcu_read_lock_sched_held+0xe/0x50
> [    1.016329]  kernel_init_freeable+0x20a/0x268
> [    1.016329]  ? rest_init+0x160/0x160
> [    1.016329]  kernel_init+0x1e/0x140
> [    1.016329]  ret_from_fork+0x22/0x30
> [    1.016329]  </TASK>
> [    1.016329] irq event stamp: 152
> [    1.016329] hardirqs last  enabled at (151): [<ffffffff91da7a4c>] _raw=
_spin_unlock_irqrestore+0x4c/0x60
> [    1.016329] hardirqs last disabled at (152): [<ffffffff91da7811>] _raw=
_spin_lock_irqsave+0x71/0x90
> [    1.016329] softirqs last  enabled at (0): [<ffffffff908a230c>] copy_p=
rocess+0xc8c/0x31b0
> [    1.016329] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [    1.016329] ---[ end trace 0000000000000000 ]---
> [    1.016329] ------------[ cut here ]------------
> [    1.016329] ODEBUG: active_state active (active state 1) object type: =
rcu_head hint: 0x0
> [    1.016329] WARNING: CPU: 0 PID: 1 at lib/debugobjects.c:502 debug_pri=
nt_object+0xda/0x100
> [    1.016329] Modules linked in:
> [    1.016329] CPU: 0 PID: 1 Comm: swapper Tainted: G        W         5.=
19.0-rc3-yoctodev-standard+ #214
> [    1.016329] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS r=
el-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> [    1.016329] RIP: 0010:debug_print_object+0xda/0x100
> [    1.016329] Code: 60 ec 45 92 e8 a7 7b a0 ff 4d 89 f9 4d 89 e8 44 89 e=
1 48 8b 14 dd 60 ec 45 92 4c 89 f6 48 c7 c7 e0 e1 45 92 e8 f9 d1 b3 00 90 <=
0f> e
> [    1.016329] RSP: 0000:ffff888001337bd0 EFLAGS: 00010082
> [    1.016329] RAX: 0000000000000000 RBX: 0000000000000003 RCX: 000000000=
0000000
> [    1.016329] RDX: 00000000ffffffd8 RSI: 0000000000000004 RDI: ffffed100=
0266f6c
> [    1.016329] RBP: ffff888001337c00 R08: ffffffff90a56ee6 R09: fffffbfff=
25df5c2
> [    1.016329] R10: ffffffff92efae0b R11: fffffbfff25df5c1 R12: 000000000=
0000001
> [    1.016329] R13: ffffffff9227f520 R14: ffffffff9245e640 R15: 000000000=
0000000
> [    1.016329] FS:  0000000000000000(0000) GS:ffffffff92cbb000(0000) knlG=
S:0000000000000000
> [    1.016329] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    1.016329] CR2: ffff888017401000 CR3: 0000000015a3c000 CR4: 000000000=
01506f0
> [    1.016329] Call Trace:
> [    1.016329]  <TASK>
> [    1.016329]  debug_object_active_state+0x1d7/0x210
> [    1.016329]  ? debug_object_deactivate+0x210/0x210
> [    1.016329]  ? lockdep_hardirqs_on_prepare+0x13/0x210
> [    1.016329]  ? call_rcu+0xde/0x150
> [    1.016329]  ? trace_hardirqs_on+0x54/0x120
> [    1.016329]  ? rcu_torture_fwd_cb_hist.cold+0xe9/0xe9
> [    1.016329]  call_rcu+0x39/0x150
> [    1.016329]  rcu_torture_init+0x1687/0x1759
> [    1.016329]  ? srcu_init+0xaa/0xaa
> [    1.016329]  ? irq_debugfs_copy_devname+0x70/0x70
> [    1.016329]  ? rcu_torture_barrier1cb+0x40/0x40
> [    1.016329]  ? rcu_torture_barrier1cb+0x40/0x40
> [    1.016329]  ? irq_pm_init_ops+0x19/0x19
> [    1.016329]  ? mutex_unlock+0x12/0x20
> [    1.016329]  ? srcu_init+0xaa/0xaa
> [    1.016329]  do_one_initcall+0xc1/0x310
> [    1.016329]  ? initcall_blacklisted+0x140/0x140
> [    1.016329]  ? parameq+0x20/0x90
> [    1.016329]  ? __kmalloc+0x238/0x5d0
> [    1.016329]  ? rcu_read_lock_sched_held+0xe/0x50
> [    1.016329]  kernel_init_freeable+0x20a/0x268
> [    1.016329]  ? rest_init+0x160/0x160
> [    1.016329]  kernel_init+0x1e/0x140
> [    1.016329]  ret_from_fork+0x22/0x30
> [    1.016329]  </TASK>
> [    1.016329] irq event stamp: 152
> [    1.016329] hardirqs last  enabled at (151): [<ffffffff91da7a4c>] _raw=
_spin_unlock_irqrestore+0x4c/0x60
> [    1.016329] hardirqs last disabled at (152): [<ffffffff91da7811>] _raw=
_spin_lock_irqsave+0x71/0x90
> [    1.016329] softirqs last  enabled at (0): [<ffffffff908a230c>] copy_p=
rocess+0xc8c/0x31b0
> [    1.016329] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [    1.016329] ---[ end trace 0000000000000000 ]---
> [    1.016329] call_rcu(): Double-freed CB (____ptrval____)->rcu_torture_=
leak_cb+0x0/0x10()!!!   non-slab/vmalloc memory
> [    1.016329] ------------[ cut here ]------------
> [    1.016329] ODEBUG: activate active (active state 1) object type: rcu_=
head hint: 0x0
> [    1.016329] WARNING: CPU: 0 PID: 1 at lib/debugobjects.c:502 debug_pri=
nt_object+0xda/0x100
> [    1.016329] Modules linked in:
> [    1.016329] CPU: 0 PID: 1 Comm: swapper Tainted: G        W         5.=
19.0-rc3-yoctodev-standard+ #214
> [    1.016329] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS r=
el-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> [    1.016329] RIP: 0010:debug_print_object+0xda/0x100
> [    1.016329] Code: 60 ec 45 92 e8 a7 7b a0 ff 4d 89 f9 4d 89 e8 44 89 e=
1 48 8b 14 dd 60 ec 45 92 4c 89 f6 48 c7 c7 e0 e1 45 92 e8 f9 d1 b3 00 90 <=
0f> e
> [    1.016329] RSP: 0000:ffff888001337be0 EFLAGS: 00010086
> [    1.016329] RAX: 0000000000000000 RBX: 0000000000000003 RCX: 000000000=
0000000
> [    1.016329] RDX: 00000000ffffffd8 RSI: 0000000000000004 RDI: ffffed100=
0266f6e
> [    1.016329] RBP: ffff888001337c10 R08: ffffffff90a56ee6 R09: fffffbfff=
25df5c2
> [    1.016329] R10: ffffffff92efae0b R11: fffffbfff25df5c1 R12: 000000000=
0000001
> [    1.016329] R13: ffffffff9227f520 R14: ffffffff9245e8a0 R15: 000000000=
0000000
> [    1.016329] FS:  0000000000000000(0000) GS:ffffffff92cbb000(0000) knlG=
S:0000000000000000
> [    1.016329] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    1.016329] CR2: ffff888017401000 CR3: 0000000015a3c000 CR4: 000000000=
01506f0
> [    1.016329] Call Trace:
> [    1.016329]  <TASK>
> [    1.016329]  debug_object_activate+0x2b9/0x300
> [    1.016329]  ? debug_object_assert_init+0x220/0x220
> [    1.016329]  ? _raw_spin_unlock+0x23/0x30
> [    1.016329]  ? find_vmap_area+0x5c/0x90
> [    1.016329]  ? do_raw_spin_unlock+0x85/0xe0
> [    1.016329]  ? rcu_torture_fwd_cb_hist.cold+0xe9/0xe9
> [    1.016329]  call_rcu+0x20/0x150
> [    1.016329]  rcu_torture_init+0x16aa/0x1759
> [    1.016329]  ? srcu_init+0xaa/0xaa
> [    1.016329]  ? irq_debugfs_copy_devname+0x70/0x70
> [    1.016329]  ? rcu_torture_barrier1cb+0x40/0x40
> [    1.016329]  ? srcu_torture_completed+0x10/0x10
> [    1.016329]  ? irq_pm_init_ops+0x19/0x19
> [    1.016329]  ? mutex_unlock+0x12/0x20
> [    1.016329]  ? srcu_init+0xaa/0xaa
> [    1.016329]  do_one_initcall+0xc1/0x310
> [    1.016329]  ? initcall_blacklisted+0x140/0x140
> [    1.016329]  ? parameq+0x20/0x90
> [    1.016329]  ? __kmalloc+0x238/0x5d0
> [    1.016329]  ? rcu_read_lock_sched_held+0xe/0x50
> [    1.016329]  kernel_init_freeable+0x20a/0x268
> [    1.016329]  ? rest_init+0x160/0x160
> [    1.016329]  kernel_init+0x1e/0x140
> [    1.016329]  ret_from_fork+0x22/0x30
> [    1.016329]  </TASK>
> [    1.016329] irq event stamp: 152
> [    1.016329] hardirqs last  enabled at (151): [<ffffffff91da7a4c>] _raw=
_spin_unlock_irqrestore+0x4c/0x60
> [    1.016329] hardirqs last disabled at (152): [<ffffffff91da7811>] _raw=
_spin_lock_irqsave+0x71/0x90
> [    1.016329] softirqs last  enabled at (0): [<ffffffff908a230c>] copy_p=
rocess+0xc8c/0x31b0
> [    1.016329] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [    1.016329] ---[ end trace 0000000000000000 ]---
> [    1.016329] ------------[ cut here ]------------
> [    1.016329] ODEBUG: active_state active (active state 1) object type: =
rcu_head hint: 0x0
> [    1.016329] WARNING: CPU: 0 PID: 1 at lib/debugobjects.c:502 debug_pri=
nt_object+0xda/0x100
> [    1.016329] Modules linked in:
> [    1.016329] CPU: 0 PID: 1 Comm: swapper Tainted: G        W         5.=
19.0-rc3-yoctodev-standard+ #214
> [    1.016329] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS r=
el-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> [    1.016329] RIP: 0010:debug_print_object+0xda/0x100
> [    1.016329] Code: 60 ec 45 92 e8 a7 7b a0 ff 4d 89 f9 4d 89 e8 44 89 e=
1 48 8b 14 dd 60 ec 45 92 4c 89 f6 48 c7 c7 e0 e1 45 92 e8 f9 d1 b3 00 90 <=
0f> e
> [    1.016329] RSP: 0000:ffff888001337bd0 EFLAGS: 00010082
> [    1.016329] RAX: 0000000000000000 RBX: 0000000000000003 RCX: 000000000=
0000000
> [    1.016329] RDX: 00000000ffffffd8 RSI: 0000000000000004 RDI: ffffed100=
0266f6c
> [    1.016329] RBP: ffff888001337c00 R08: ffffffff90a56ee6 R09: fffffbfff=
25df5c2
> [    1.016329] R10: ffffffff92efae0b R11: fffffbfff25df5c1 R12: 000000000=
0000001
> [    1.016329] R13: ffffffff9227f520 R14: ffffffff9245e640 R15: 000000000=
0000000
> [    1.016329] FS:  0000000000000000(0000) GS:ffffffff92cbb000(0000) knlG=
S:0000000000000000
> [    1.016329] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    1.016329] CR2: ffff888017401000 CR3: 0000000015a3c000 CR4: 000000000=
01506f0
> [    1.016329] Call Trace:
> [    1.016329]  <TASK>
> [    1.016329]  debug_object_active_state+0x1d7/0x210
> [    1.016329]  ? debug_object_deactivate+0x210/0x210
> [    1.016329]  ? _raw_spin_unlock+0x23/0x30
> [    1.016329]  ? find_vmap_area+0x5c/0x90
> [    1.016329]  ? do_raw_spin_unlock+0x85/0xe0
> [    1.016329]  ? rcu_torture_fwd_cb_hist.cold+0xe9/0xe9
> [    1.016329]  call_rcu+0x39/0x150
> [    1.016329]  rcu_torture_init+0x16aa/0x1759
> [    1.016329]  ? srcu_init+0xaa/0xaa
> [    1.016329]  ? irq_debugfs_copy_devname+0x70/0x70
> [    1.016329]  ? rcu_torture_barrier1cb+0x40/0x40
> [    1.016329]  ? srcu_torture_completed+0x10/0x10
> [    1.016329]  ? irq_pm_init_ops+0x19/0x19
> [    1.016329]  ? mutex_unlock+0x12/0x20
> [    1.016329]  ? srcu_init+0xaa/0xaa
> [    1.016329]  do_one_initcall+0xc1/0x310
> [    1.016329]  ? initcall_blacklisted+0x140/0x140
> [    1.016329]  ? parameq+0x20/0x90
> [    1.016329]  ? __kmalloc+0x238/0x5d0
> [    1.016329]  ? rcu_read_lock_sched_held+0xe/0x50
> [    1.016329]  kernel_init_freeable+0x20a/0x268
> [    1.016329]  ? rest_init+0x160/0x160
> [    1.016329]  kernel_init+0x1e/0x140
> [    1.016329]  ret_from_fork+0x22/0x30
> [    1.016329]  </TASK>
> [    1.016329] irq event stamp: 152
> [    1.016329] hardirqs last  enabled at (151): [<ffffffff91da7a4c>] _raw=
_spin_unlock_irqrestore+0x4c/0x60
> [    1.016329] hardirqs last disabled at (152): [<ffffffff91da7811>] _raw=
_spin_lock_irqsave+0x71/0x90
> [    1.016329] softirqs last  enabled at (0): [<ffffffff908a230c>] copy_p=
rocess+0xc8c/0x31b0
> [    1.016329] softirqs last disabled at (0): [<0000000000000000>] 0x0
> [    1.016329] ---[ end trace 0000000000000000 ]---
> [    1.016329] call_rcu(): Double-freed CB (____ptrval____)->rcu_torture_=
leak_cb+0x0/0x10()!!!   slab kmalloc-16 start ffff888003f49240 pointer offs=
et 06
> [    1.101401] rcu-torture: rcu_torture_read_exit: Start of test
>=20
> Thanks
> Zqiang
>=20
>=20
> >
> >							Thanx, Paul
>=20
> > ---
> >  v1->v2:
> >  for do duplicate kvfree_call_rcu(), not set leak callbacks.=20
> >=20
> >  kernel/rcu/tiny.c | 17 ++++++++++++++++-
> >  1 file changed, 16 insertions(+), 1 deletion(-)
> >=20
> > diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
> > index f0561ee16b9c..943d431b908f 100644
> > --- a/kernel/rcu/tiny.c
> > +++ b/kernel/rcu/tiny.c
> > @@ -158,6 +158,10 @@ void synchronize_rcu(void)
> >  }
> >  EXPORT_SYMBOL_GPL(synchronize_rcu);
> > =20
> > +static void tiny_rcu_leak_callback(struct rcu_head *rhp)
> > +{
> > +}
> > +
> >  /*
> >   * Post an RCU callback to be invoked after the end of an RCU grace
> >   * period.  But since we have but one CPU, that would be after any
> > @@ -165,9 +169,20 @@ EXPORT_SYMBOL_GPL(synchronize_rcu);
> >   */
> >  void call_rcu(struct rcu_head *head, rcu_callback_t func)
> >  {
> > +	static atomic_t doublefrees;
> >  	unsigned long flags;
> > =20
> > -	debug_rcu_head_queue(head);
> > +	if (debug_rcu_head_queue(head)) {
> > +		if (atomic_inc_return(&doublefrees) < 4) {
> > +			pr_err("%s(): Double-freed CB %p->%pS()!!!  ", __func__, head, head=
->func);
> > +			mem_dump_obj(head);
> > +		}
> > +
> > +		if (!__is_kvfree_rcu_offset((unsigned long)head->func))
> > +			WRITE_ONCE(head->func, tiny_rcu_leak_callback);
> > +		return;
> > +	}
> > +
> >  	head->func =3D func;
> >  	head->next =3D NULL;
> > =20
> > --=20
> > 2.25.1
> >=20