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Date: Wed, 18 May 2022 04:21:07 +0000
From: "Zhang, Qiang1" <qiang1.zhang@...el.com>
To: "Zhang, Qiang1" <qiang1.zhang@...el.com>,
"paulmck@...nel.org" <paulmck@...nel.org>
CC: "frederic@...nel.org" <frederic@...nel.org>,
"rcu@...r.kernel.org" <rcu@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] rcu: Remove debug_object_active_state() from
debug_rcu_head_queue/unqueue()
On Fri, May 13, 2022 at 01:03:19AM +0000, Zhang, Qiang1 wrote:
> On Tue, May 10, 2022 at 11:07:48AM +0800, Zqiang wrote:
> > Currently, the double call_rcu() detected only need call
> > debug_object_activate() to check whether the rcu head object is
> > activated, the rcu head object usage state check is not necessary
> > and when call rcu_test_debug_objects() the
> > debug_object_active_state() will output same callstack as
> > debug_object_activate(). so remove
> > debug_object_active_state() to reduce the output of repeated callstack.
> >
> > Signed-off-by: Zqiang <qiang1.zhang@...el.com>
> >
> >Could you please post the output of the dmesg output of a failed check with your change?
> >
>
> Original output:
>
> [ 0.818279] ODEBUG: activate active (active state 1) object type: rcu_head hint: 0x0
> [ 0.818296] WARNING: CPU: 1 PID: 1 at lib/debugobjects.c:505 debug_print_object+0xd8/0xf0
> [ 0.818301] Modules linked in:
> [ 0.818304] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G W 5.18.0-rc6-next-20220511-yoctodev-standard+ #75
> [ 0.818306] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> [ 0.818308] RIP: 0010:debug_print_object+0xd8/0xf0
> [ 0.818311] Code: dd 40 9e 03 9d e8 48 62 a2 ff 4d 89 f9 4d 89 e8 44 89 e1 48 8b 14 dd 40 9e 03 9d 4c 89 f6 48 c7 c7 c0 93 03 9d e8 f6 1a b1 00 <0f> f
> [ 0.818313] RSP: 0000:ffff88810033fad0 EFLAGS: 00010082
> [ 0.818315] RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
> [ 0.818317] RDX: 0000000000000002 RSI: 0000000000000004 RDI: ffffed1020067f4c
> [ 0.818319] RBP: ffff88810033fb00 R08: ffffffff9b50d898 R09: fffffbfff3bf5c6d
> [ 0.818320] R10: 0000000000000003 R11: fffffbfff3bf5c6c R12: 0000000000000001
> [ 0.818322] R13: ffffffff9ce769a0 R14: ffffffff9d039a80 R15: 0000000000000000
> [ 0.818324] FS: 0000000000000000(0000) GS:ffff888158880000(0000) knlGS:0000000000000000
> [ 0.818327] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 0.818329] CR2: 0000000000000000 CR3: 000000017600e000 CR4: 00000000001506e0
> [ 0.818330] Call Trace:
> [ 0.818331] <TASK>
> [ 0.818333] debug_object_activate+0x2b8/0x300
> [ 0.818336] ? debug_object_assert_init+0x220/0x220
> [ 0.818340] ? __kasan_check_write+0x14/0x20
> [ 0.818343] call_rcu+0x98/0x1110
> [ 0.818347] ? vprintk+0x4c/0x60
> [ 0.818350] ? rcu_torture_fwd_cb_hist.cold+0xe9/0xe9
> [ 0.818354] ? strict_work_handler+0x70/0x70
> [ 0.818357] rcu_torture_init+0x18be/0x199e
> [ 0.818361] ? srcu_init+0x133/0x133
> [ 0.818364] ? __mutex_unlock_slowpath.isra.0+0x270/0x270
> [ 0.818368] ? rcu_torture_barrier1cb+0x40/0x40
> [ 0.818371] ? rcu_torture_barrier1cb+0x40/0x40
> [ 0.818374] ? srcu_init+0x133/0x133
> [ 0.818377] do_one_initcall+0xb3/0x300
> [ 0.818380] ? initcall_blacklisted+0x150/0x150
> [ 0.818382] ? parameq+0x70/0x90
> [ 0.818385] ? __kasan_check_read+0x11/0x20
> [ 0.818389] kernel_init_freeable+0x2b2/0x310
> [ 0.818392] ? rest_init+0xf0/0xf0
> [ 0.818396] kernel_init+0x1e/0x140
> [ 0.818399] ret_from_fork+0x22/0x30
> [ 0.818402] </TASK>
> [ 0.818403] ---[ end trace 0000000000000000 ]---
> [ 0.818405] ------------[ cut here ]------------
> [ 0.818405] ODEBUG: active_state active (active state 1) object type: rcu_head hint: 0x0
> [ 0.818421] WARNING: CPU: 1 PID: 1 at lib/debugobjects.c:505 debug_print_object+0xd8/0xf0
> [ 0.818424] Modules linked in:
> [ 0.818426] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G W 5.18.0-rc6-next-20220511-yoctodev-standard+ #75
> [ 0.818428] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> [ 0.818430] RIP: 0010:debug_print_object+0xd8/0xf0
> [ 0.818432] Code: dd 40 9e 03 9d e8 48 62 a2 ff 4d 89 f9 4d 89 e8 44 89 e1 48 8b 14 dd 40 9e 03 9d 4c 89 f6 48 c7 c7 c0 93 03 9d e8 f6 1a b1 00 <0f> f
> [ 0.818435] RSP: 0000:ffff88810033fac0 EFLAGS: 00010086
> [ 0.818437] RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
> [ 0.818438] RDX: 0000000000000002 RSI: 0000000000000004 RDI: ffffed1020067f4a
> [ 0.818440] RBP: ffff88810033faf0 R08: ffffffff9b50d898 R09: fffffbfff3bf5c6d
> [ 0.818441] R10: 0000000000000003 R11: fffffbfff3bf5c6c R12: 0000000000000001
> [ 0.818443] R13: ffffffff9ce769a0 R14: ffffffff9d039820 R15: 0000000000000000
> [ 0.818445] FS: 0000000000000000(0000) GS:ffff888158880000(0000) knlGS:0000000000000000
> [ 0.818448] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 0.818449] CR2: 0000000000000000 CR3: 000000017600e000 CR4: 00000000001506e0
> [ 0.818451] Call Trace:
> [ 0.818452] <TASK>
> [ 0.818453] debug_object_active_state+0x1d6/0x210
> [ 0.818456] ? debug_object_deactivate+0x210/0x210
> [ 0.818460] ? __kasan_check_write+0x14/0x20
> [ 0.818464] call_rcu+0xb7/0x1110
> [ 0.818466] ? vprintk+0x4c/0x60
> [ 0.818469] ? rcu_torture_fwd_cb_hist.cold+0xe9/0xe9
> [ 0.818472] ? strict_work_handler+0x70/0x70
> [ 0.818476] rcu_torture_init+0x18be/0x199e
> [ 0.818479] ? srcu_init+0x133/0x133
> [ 0.818482] ? __mutex_unlock_slowpath.isra.0+0x270/0x270
> [ 0.818486] ? rcu_torture_barrier1cb+0x40/0x40
> [ 0.818489] ? rcu_torture_barrier1cb+0x40/0x40
> [ 0.818492] ? srcu_init+0x133/0x133
> [ 0.818495] do_one_initcall+0xb3/0x300
> [ 0.818497] ? initcall_blacklisted+0x150/0x150
> [ 0.818500] ? parameq+0x70/0x90
> [ 0.818503] ? __kasan_check_read+0x11/0x20
> [ 0.818507] kernel_init_freeable+0x2b2/0x310
> [ 0.818510] ? rest_init+0xf0/0xf0
> [ 0.818513] kernel_init+0x1e/0x140
> [ 0.818515] ret_from_fork+0x22/0x30
> [ 0.818519] </TASK>
> [ 0.818520] ---[ end trace 0000000000000000 ]---
> [ 0.818521] rcu: call_rcu(): Double-freed CB 00000000e2817fcb->rcu_torture_leak_cb+0x0/0x10()!!! non-slab/vmalloc memory
>
>
> After apply this patch:
>
> [ 0.647048] ODEBUG: activate active (active state 0) object type: rcu_head hint: 0x0
> [ 0.647068] WARNING: CPU: 1 PID: 1 at lib/debugobjects.c:505 debug_print_object+0xd8/0xf0
> [ 0.647073] Modules linked in:
> [ 0.647075] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G W 5.18.0-rc6-next-20220511-yoctodev-standard+ #77
> [ 0.647078] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> [ 0.647080] RIP: 0010:debug_print_object+0xd8/0xf0
> [ 0.647083] Code: dd 80 9d 43 a2 e8 38 62 a2 ff 4d 89 f9 4d 89 e8 44 89 e1 48 8b 14 dd 80 9d 43 a2 4c 89 f6 48 c7 c7 00 93 43 a2 e8 f6 1a b1 00 <0f> 0b 83 05 7b 62f
> [ 0.647085] RSP: 0000:ffff88810033fad0 EFLAGS: 00010082
> [ 0.647088] RAX: 0000000000000000 RBX: 0000000000000003 RCX: 0000000000000000
> [ 0.647090] RDX: 0000000000000002 RSI: 0000000000000004 RDI: ffffed1020067f4c
> [ 0.647091] RBP: ffff88810033fb00 R08: ffffffffa090d898 R09: fffffbfff467586d
> [ 0.647093] R10: 0000000000000003 R11: fffffbfff467586c R12: 0000000000000000
> [ 0.647095] R13: ffffffffa22769a0 R14: ffffffffa24399c0 R15: 0000000000000000
> [ 0.647097] FS: 0000000000000000(0000) GS:ffff88815b880000(0000) knlGS:0000000000000000
> [ 0.647100] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 0.647102] CR2: 0000000000000000 CR3: 000000002f20e000 CR4: 00000000001506e0
> [ 0.647104] Call Trace:
> [ 0.647104] <TASK>
> [ 0.647106] debug_object_activate+0x2b8/0x300
> [ 0.647110] ? debug_object_assert_init+0x220/0x220
> [ 0.647114] ? __kasan_check_write+0x14/0x20
> [ 0.647118] call_rcu+0x98/0x1100
> [ 0.647121] ? vprintk+0x4c/0x60
> [ 0.647125] ? rcu_torture_fwd_cb_hist.cold+0xe9/0xe9
> [ 0.647129] ? strict_work_handler+0x50/0x50
> [ 0.647133] rcu_torture_init+0x18be/0x199e
> [ 0.647136] ? srcu_init+0x133/0x133
> [ 0.647140] ? __mutex_unlock_slowpath.isra.0+0x270/0x270
> [ 0.647144] ? rcu_torture_barrier1cb+0x40/0x40
> [ 0.647148] ? rcu_torture_barrier1cb+0x40/0x40
> [ 0.647151] ? srcu_init+0x133/0x133
> [ 0.647155] do_one_initcall+0xb3/0x300
> [ 0.647157] ? initcall_blacklisted+0x150/0x150
> [ 0.647160] ? parameq+0x70/0x90
> [ 0.647164] ? __kasan_check_read+0x11/0x20
> [ 0.647167] kernel_init_freeable+0x2b2/0x310
> [ 0.647171] ? rest_init+0xf0/0xf0
> [ 0.647174] kernel_init+0x1e/0x140
> [ 0.647177] ret_from_fork+0x22/0x30
> [ 0.647181] </TASK>
> [ 0.647182] ---[ end trace 0000000000000000 ]---
> [ 0.647184] rcu: call_rcu(): Double-freed CB 000000009a684b70->rcu_torture_leak_cb+0x0/0x10()!!! non-slab/vmalloc memory
>Very good, and thank you!
>
>Now suppose that someone passes a pointer to call_rcu(), but then invokes kfree() on that same object before the grace period ends.
>Is the offending kfree() flagged?
>
>If the CONFIG_DEBUG_OBJECTS_FREE is enabled, the debug_check_no_obj_freed() will check wether the object is activated in kfree() If is activated, also output callstack.
>
>__debug_check_no_obj_freed()
>{........
> switch (obj->state) {
> case ODEBUG_STATE_ACTIVE:
> descr = obj->descr;
> state = obj->state;
> _spin_unlock_irqrestore(&db->lock, flags);
> debug_print_object(obj, "free");
> }
>.........
>}
Hi Paul
The __debug_check_no_obj_freed() only check obj->state, don't care obj->astate,
the debug_object_active_state() is not necessary. If CONFIG_DEBUG_OBJECTS_FREE is not enabled,
the kfree() will directly release it without check obj state.
Any thoughts?
Thanks,
Zqiang
>Thanks,
>Zqiang
>
> Thanx, Paul
> Thanks,
> Zqiang
>
>
>
> > Thanx, Paul
> >
> > ---
> > kernel/rcu/rcu.h | 13 +------------
> > 1 file changed, 1 insertion(+), 12 deletions(-)
> >
> > diff --git a/kernel/rcu/rcu.h b/kernel/rcu/rcu.h index
> > 15b96f990774..0604ecd16627 100644
> > --- a/kernel/rcu/rcu.h
> > +++ b/kernel/rcu/rcu.h
> > @@ -179,27 +179,16 @@ static inline unsigned long rcu_seq_diff(unsigned long new, unsigned long old)
> > */
> >
> > #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD
> > -# define STATE_RCU_HEAD_READY 0
> > -# define STATE_RCU_HEAD_QUEUED 1
> >
> > extern const struct debug_obj_descr rcuhead_debug_descr;
> >
> > static inline int debug_rcu_head_queue(struct rcu_head *head) {
> > - int r1;
> > -
> > - r1 = debug_object_activate(head, &rcuhead_debug_descr);
> > - debug_object_active_state(head, &rcuhead_debug_descr,
> > - STATE_RCU_HEAD_READY,
> > - STATE_RCU_HEAD_QUEUED);
> > - return r1;
> > + return debug_object_activate(head, &rcuhead_debug_descr);
> > }
> >
> > static inline void debug_rcu_head_unqueue(struct rcu_head *head) {
> > - debug_object_active_state(head, &rcuhead_debug_descr,
> > - STATE_RCU_HEAD_QUEUED,
> > - STATE_RCU_HEAD_READY);
> > debug_object_deactivate(head, &rcuhead_debug_descr); }
> > #else /* !CONFIG_DEBUG_OBJECTS_RCU_HEAD */
> > --
> > 2.25.1
> >
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