On Fri, Feb 21, 2025 at 02:59:41PM +0800, Oliver Sang wrote:
> hi, Paul,
>
> On Wed, Feb 19, 2025 at 08:51:45AM -0800, Paul E. McKenney wrote:
> > On Mon, Feb 17, 2025 at 02:30:16PM +0800, kernel test robot wrote:
> > >
> > > hi, Ankur Arora and all,
> > >
> > > this is not a regression report as our bot normally does. this report is just
> > > FYI that we observe a WARNING with this config, in case it could supply any
> > > useful information and/or somebody wants to have a look.
> > >
> > > by this change, the config has below diff with parent:
> > >
> > > ==================== PARENT FIRST_BAD KCONFIGS f001b7165def8f7af6ce95d08f0e1bbc2442654d ====================
> > > --- /pkg/linux/i386-randconfig-r121-20250212/gcc-12/f001b7165def8f7af6ce95d08f0e1bbc2442654d/.config 2025-02-13 07:56:33.420457682 +0800
> > > +++ /pkg/linux/i386-randconfig-r121-20250212/gcc-12/c9b55f9da0d2c72c8c8d8cd5df84af5251b74283/.config 2025-02-13 08:43:08.186415593 +0800
> > > @@ -147,7 +147,6 @@ CONFIG_BSD_PROCESS_ACCT=y
> > > # RCU Subsystem
> > > #
> > > CONFIG_TREE_RCU=y
> > > -CONFIG_PREEMPT_RCU=y
> > > CONFIG_RCU_EXPERT=y
> > > CONFIG_TREE_SRCU=y
> > > CONFIG_TASKS_RCU_GENERIC=y
> > > @@ -162,7 +161,6 @@ CONFIG_RCU_STALL_COMMON=y
> > > CONFIG_RCU_NEED_SEGCBLIST=y
> > > CONFIG_RCU_FANOUT=32
> > > CONFIG_RCU_FANOUT_LEAF=16
> > > -# CONFIG_RCU_BOOST is not set
> > > # CONFIG_RCU_NOCB_CPU is not set
> > > # CONFIG_TASKS_TRACE_RCU_READ_MB is not set
> > > # CONFIG_RCU_DOUBLE_CHECK_CB_TIME is not set
> > >
> > >
> > > below is full report.
> > >
> > >
> > > Hello,
> > >
> > > kernel test robot noticed "WARNING:at_kernel/rcu/rcutorture.c:#rcutorture_one_extend_check[rcutorture]" on:
> > >
> > > commit: c9b55f9da0d2c72c8c8d8cd5df84af5251b74283 ("rcu: limit PREEMPT_RCU configurations")
> > > https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master
> > >
> > > [test failed on linux-next/master c674aa7c289e51659e40dda0f954886ef7f80042]
> > >
> > > in testcase: rcutorture
> > > version:
> > > with following parameters:
> > >
> > > runtime: 300s
> > > test: cpuhotplug
> > > torture_type: rcu
> > >
> > >
> > >
> > > config: i386-randconfig-r121-20250212
> > > compiler: gcc-12
> > > test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
> > >
> > > (please refer to attached dmesg/kmsg for entire log/backtrace)
> > >
> > >
> > > +-----------------------------------------------------------------------------+------------+------------+
> > > | | f001b7165d | c9b55f9da0 |
> > > +-----------------------------------------------------------------------------+------------+------------+
> > > | WARNING:at_kernel/rcu/rcutorture.c:#rcutorture_one_extend_check[rcutorture] | 0 | 12 |
> > > | EIP:rcutorture_one_extend_check | 0 | 12 |
> > > +-----------------------------------------------------------------------------+------------+------------+
> > >
> > >
> > > If you fix the issue in a separate patch/commit (i.e. not just a new version of
> > > the same patch/commit), kindly add following tags
> > > | Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> > > | Closes: https://lore.kernel.org/oe-lkp/202502171415.8ec87c87-lkp@xxxxxxxxx
> > >
> > >
> > > The kernel config and materials to reproduce are available at:
> > > https://download.01.org/0day-ci/archive/20250217/202502171415.8ec87c87-lkp@xxxxxxxxx
> > >
> > >
> > > [ 109.553253][ T781] rcu-torture: rcu_torture_reader task started
> > > [ 109.553258][ T781] ------------[ cut here ]------------
> > > [ 109.553259][ T781] rcutorture_one_extend_check during change: Current 0x4 To add 0x4 To remove 0x0 preempt_count() 0x1
> > > [ 109.553292][ T781] WARNING: CPU: 1 PID: 781 at kernel/rcu/rcutorture.c:1905 rcutorture_one_extend_check+0x25a/0x267 [rcutorture]
> > > [ 109.553302][ T781] Modules linked in: rcutorture(+) torture
> > > [ 109.553307][ T781] CPU: 1 UID: 0 PID: 781 Comm: rcu_torture_rea Tainted: G T 6.14.0-rc1-00007-gc9b55f9da0d2 #1
> > > [ 109.553310][ T781] Tainted: [T]=RANDSTRUCT
> > > [ 109.553311][ T781] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> > > [ 109.553312][ T781] EIP: rcutorture_one_extend_check+0x25a/0x267 [rcutorture]
> > > [ 109.553318][ T781] Code: 75 2d c6 05 fd 04 1c f1 01 64 a1 84 77 7c 97 25 ff ff ff 7f 50 ff 75 08 57 53 56 68 60 9f 1c f1 68 a4 74 1c f1 e8 8d d3 ca a3 <0f> 0b 83 c4 1c 8d 65 f4 5b 5e 5f 5d c3 55 31 d2 83 f8 1f 89 e5 53
> > > [ 109.553320][ T781] EAX: 00000066 EBX: 00000004 ECX: 00000027 EDX: e89c1a00
> > > [ 109.553322][ T781] ESI: f11c92d9 EDI: 00000004 EBP: 825d1d88 ESP: 825d1d54
> > > [ 109.553323][ T781] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010282
> > > [ 109.553327][ T781] CR0: 80050033 CR2: 77235000 CR3: 010c5000 CR4: 00040690
> > > [ 109.553328][ T781] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> > > [ 109.553330][ T781] DR6: fffe0ff0 DR7: 00000400
> > > [ 109.553331][ T781] Call Trace:
> > > [ 109.553333][ T781] ? show_regs+0x4c/0x52
> > > [ 109.553343][ T781] ? rcutorture_one_extend_check+0x25a/0x267 [rcutorture]
> > > [ 109.553349][ T781] ? __warn+0x9e/0x15f
> > > [ 109.553354][ T781] ? report_bug+0xe8/0x14a
> > > [ 109.553357][ T781] ? rcutorture_one_extend_check+0x25a/0x267 [rcutorture]
> > > [ 109.553364][ T781] ? exc_overflow+0x37/0x37
> > > [ 109.553367][ T781] ? handle_bug+0x3a/0x55
> > > [ 109.553369][ T781] ? exc_invalid_op+0x1a/0x56
> > > [ 109.553372][ T781] ? handle_exception+0x148/0x148
> > > [ 109.553376][ T781] ? osq_wait_next+0x18/0x41
> > > [ 109.553379][ T781] ? exc_overflow+0x37/0x37
> > > [ 109.553381][ T781] ? rcutorture_one_extend_check+0x25a/0x267 [rcutorture]
> > > [ 109.553388][ T781] ? exc_overflow+0x37/0x37
> > > [ 109.553390][ T781] ? rcutorture_one_extend_check+0x25a/0x267 [rcutorture]
> > > [ 109.553399][ T781] rcutorture_one_extend+0x18c/0x3c1 [rcutorture]
> > > [ 109.553410][ T781] rcu_torture_one_read+0x95/0x4d2 [rcutorture]
> > > [ 109.553417][ T781] ? validate_chain+0x3d/0x24c
> > > [ 109.553420][ T781] ? mark_lock+0x6a/0x14d
> > > [ 109.553440][ T781] rcu_torture_reader+0xc4/0xdbd [rcutorture]
> > > [ 109.553448][ T781] ? rcu_torture_one_read+0x4d2/0x4d2 [rcutorture]
> > > [ 109.553457][ T781] kthread+0x169/0x16e
> > > [ 109.553459][ T781] ? rcu_torture_read_exit_child+0x3a/0x3a [rcutorture]
> > > [ 109.553466][ T781] ? kthread_is_per_cpu+0x17/0x17
> > > [ 109.553468][ T781] ret_from_fork+0x19/0x2c
> > > [ 109.553471][ T781] ? kthread_is_per_cpu+0x17/0x17
> > > [ 109.553472][ T781] ret_from_fork_asm+0x12/0x20
> > > [ 109.553475][ T781] entry_INT80_32+0x108/0x108
> > > [ 109.553481][ T781] irq event stamp: 307
> > > [ 109.553482][ T781] hardirqs last enabled at (313): [<94ebb6cb>] console_trylock_spinning+0x6b/0x10a
> > > [ 109.553485][ T781] hardirqs last disabled at (318): [<94ebb691>] console_trylock_spinning+0x31/0x10a
> > > [ 109.553486][ T781] softirqs last enabled at (0): [<94e613c4>] copy_process+0x945/0x1a7d
> > > [ 109.553489][ T781] softirqs last disabled at (0): [<00000000>] 0x0
> > > [ 109.553491][ T781] ---[ end trace 0000000000000000 ]---
> > > [ 109.553494][ T781] ------------[ cut here ]------------
> > > [ 109.553496][ T781] rcutorture_one_extend_check after change: Current 0x60 To add 0x60 To remove 0x4 preempt_count() 0x2
> > > [ 109.553510][ T781] WARNING: CPU: 1 PID: 781 at kernel/rcu/rcutorture.c:1902 rcutorture_one_extend_check+0x20d/0x267 [rcutorture]
> > > [ 109.553517][ T781] Modules linked in: rcutorture(+) torture
> > > [ 109.553520][ T781] CPU: 1 UID: 0 PID: 781 Comm: rcu_torture_rea Tainted: G W T 6.14.0-rc1-00007-gc9b55f9da0d2 #1
> > > [ 109.553523][ T781] Tainted: [W]=WARN, [T]=RANDSTRUCT
> > > [ 109.553524][ T781] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> > > [ 109.553525][ T781] EIP: rcutorture_one_extend_check+0x20d/0x267 [rcutorture]
> > > [ 109.553530][ T781] Code: 3d fe 04 1c f1 00 75 27 25 ff ff ff 7f c6 05 fe 04 1c f1 01 50 ff 75 08 57 53 56 68 60 9f 1c f1 68 a4 74 1c f1 e8 da d3 ca a3 <0f> 0b 83 c4 1c a1 40 09 1c f1 8b 40 1c 85 c0 74 41 f6 c3 60 75 3c
> > > [ 109.553532][ T781] EAX: 00000067 EBX: 00000060 ECX: 00000027 EDX: e89c1a00
> > > [ 109.553533][ T781] ESI: f11c936d EDI: 00000060 EBP: 825d1d88 ESP: 825d1d54
> > > [ 109.553535][ T781] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00010282
> > > [ 109.553537][ T781] CR0: 80050033 CR2: 77235000 CR3: 010c5000 CR4: 00040690
> > > [ 109.553539][ T781] DR0: 00000000 DR1: 00000000 DR2: 00000000 DR3: 00000000
> > > [ 109.553540][ T781] DR6: fffe0ff0 DR7: 00000400
> > > [ 109.553541][ T781] Call Trace:
> > > [ 109.553543][ T781] ? show_regs+0x4c/0x52
> > > [ 109.553545][ T781] ? rcutorture_one_extend_check+0x20d/0x267 [rcutorture]
> > > [ 109.553551][ T781] ? __warn+0x9e/0x15f
> > > [ 109.553555][ T781] ? report_bug+0xe8/0x14a
> > > [ 109.553558][ T781] ? rcutorture_one_extend_check+0x20d/0x267 [rcutorture]
> > > [ 109.553565][ T781] ? exc_overflow+0x37/0x37
> > > [ 109.553567][ T781] ? handle_bug+0x3a/0x55
> > > [ 109.553569][ T781] ? exc_invalid_op+0x1a/0x56
> > > [ 109.553572][ T781] ? handle_exception+0x148/0x148
> > > [ 109.553575][ T781] ? osq_wait_next+0x18/0x41
> > > [ 109.553578][ T781] ? exc_overflow+0x37/0x37
> > > [ 109.553580][ T781] ? rcutorture_one_extend_check+0x20d/0x267 [rcutorture]
> > > [ 109.553587][ T781] ? exc_overflow+0x37/0x37
> > > [ 109.553589][ T781] ? rcutorture_one_extend_check+0x20d/0x267 [rcutorture]
> > > [ 109.553599][ T781] rcutorture_one_extend+0x3b7/0x3c1 [rcutorture]
> > > [ 109.553610][ T781] rcu_torture_one_read+0x21b/0x4d2 [rcutorture]
> > > [ 109.553638][ T781] rcu_torture_reader+0xc4/0xdbd [rcutorture]
> > > [ 109.553646][ T781] ? rcu_torture_one_read+0x4d2/0x4d2 [rcutorture]
> > > [ 109.553655][ T781] kthread+0x169/0x16e
> > > [ 109.553658][ T781] ? rcu_torture_read_exit_child+0x3a/0x3a [rcutorture]
> > > [ 109.553664][ T781] ? kthread_is_per_cpu+0x17/0x17
> > > [ 109.553667][ T781] ret_from_fork+0x19/0x2c
> > > [ 109.553669][ T781] ? kthread_is_per_cpu+0x17/0x17
> > > [ 109.553671][ T781] ret_from_fork_asm+0x12/0x20
> > > [ 109.553673][ T781] entry_INT80_32+0x108/0x108
> > > [ 109.553679][ T781] irq event stamp: 607
> > > [ 109.553680][ T781] hardirqs last enabled at (613): [<94ebb6cb>] console_trylock_spinning+0x6b/0x10a
> > > [ 109.553682][ T781] hardirqs last disabled at (618): [<94ebb691>] console_trylock_spinning+0x31/0x10a
> > > [ 109.553684][ T781] softirqs last enabled at (0): [<94e613c4>] copy_process+0x945/0x1a7d
> > > [ 109.553686][ T781] softirqs last disabled at (0): [<00000000>] 0x0
> > > [ 109.553688][ T781] ---[ end trace 0000000000000000 ]---
> > > [ 109.634034][ T769] rcu-torture: Creating torture_shuffle task
> > > [ 109.635952][ T782] rcu-torture: rcu_torture_stats task started
> > > [ 109.637994][ T769] rcu-torture: Creating torture_stutter task
> >
> > And rcutorture's WARN_ON() has a bug that is exposed by that change
> > in Kconfig option. Does the patch shown below help?
>
> the patch does not fix the WARNING in our tests. attached one dmesg FYI.
Just to make sure that I understand, this patch was applied against this
commit, correct?
c9b55f9da0d2 ("rcu: limit PREEMPT_RCU configurations")
I am guessing this based on this dmesg line:
[ 109.553307][ T781] CPU: 1 UID: 0 PID: 781 Comm: rcu_torture_rea Tainted: G T 6.14.0-rc1-00007-gc9b55f9da0d2 #1
Is this really the case, or am I confused?
Thanx, Paul
> > Either way, thank you for your testing efforts!
> >
> > Thanx, Paul
> >
> > ------------------------------------------------------------------------
> >
> > commit bb638fe1a683316397d5517cb7d1797d70d21c86
> > Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
> > Date: Wed Feb 19 08:41:11 2025 -0800
> >
> > rcutorture: Update rcutorture_one_extend_check() for lazy preemption
> >
> > The rcutorture_one_extend_check() function's last check assumes that
> > if cur_ops->readlock_nesting() returns greater than zero, either the
> > RCUTORTURE_RDR_RCU_1 or the RCUTORTURE_RDR_RCU_2 bit must be set, that
> > is, there must be at least one rcu_read_lock() in effect.
> >
> > This works for preemptible RCU and for non-preemptible RCU running in
> > a non-preemptible kernel. But it fails for non-preemptible RCU running
> > in a preemptible kernel because then RCU's cur_ops->readlock_nesting()
> > function, which is rcu_torture_readlock_nesting(), will return
> > the PREEMPT_MASK mask bits from preempt_count(). The result will
> > be greater than zero if preemption is disabled, including by the
> > RCUTORTURE_RDR_PREEMPT and RCUTORTURE_RDR_SCHED bits.
> >
> > This commit therefore adjusts this check to take into account the case
> > fo non-preemptible RCU running in a preemptible kernel.
> >
> > Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
> > Closes: https://lore.kernel.org/oe-lkp/202502171415.8ec87c87-lkp@xxxxxxxxx
> > Co-developed-by: Boqun Feng <boqun.feng@xxxxxxxxx>
> > Signed-off-by: Boqun Feng <boqun.feng@xxxxxxxxx>
> > Co-developed-by: Joel Fernandes <joelagnelf@xxxxxxxxxx>
> > Signed-off-by: Joel Fernandes <joelagnelf@xxxxxxxxxx>
> > Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> >
> > diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> > index 895a27545ae1e..0f446ff04eda1 100644
> > --- a/kernel/rcu/rcutorture.c
> > +++ b/kernel/rcu/rcutorture.c
> > @@ -1981,6 +1981,8 @@ static void rcu_torture_reader_do_mbchk(long myid, struct rcu_torture *rtp,
> > #define ROEC_ARGS "%s %s: Current %#x To add %#x To remove %#x preempt_count() %#x\n", __func__, s, curstate, new, old, preempt_count()
> > static void rcutorture_one_extend_check(char *s, int curstate, int new, int old, bool insoftirq)
> > {
> > + int mask;
> > +
> > if (!IS_ENABLED(CONFIG_RCU_TORTURE_TEST_CHK_RDR_STATE))
> > return;
> >
> > @@ -2010,8 +2012,10 @@ static void rcutorture_one_extend_check(char *s, int curstate, int new, int old,
> > WARN_ONCE(cur_ops->extendables &&
> > !(curstate & (RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED)) &&
> > (preempt_count() & PREEMPT_MASK), ROEC_ARGS);
> > - WARN_ONCE(cur_ops->readlock_nesting &&
> > - !(curstate & (RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2)) &&
> > + mask = RCUTORTURE_RDR_RCU_1 | RCUTORTURE_RDR_RCU_2;
> > + if (IS_ENABLED(CONFIG_PREEMPT_RCU))
> > + mask |= RCUTORTURE_RDR_PREEMPT | RCUTORTURE_RDR_SCHED;
> > + WARN_ONCE(cur_ops->readlock_nesting && !(curstate & mask) &&
> > cur_ops->readlock_nesting() > 0, ROEC_ARGS);
> > }
> >
> >
