| Message ID | 20240216194329.840555-1-mcgrof@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | test_xarray: fix soft lockup for advanced-api tests | expand |
On Fri, 16 Feb 2024 11:43:29 -0800 Luis Chamberlain <mcgrof@kernel.org> wrote: > The new adanced API tests So this is a fix against the mm-unstable series "test_xarray: advanced API multi-index tests", v2. > want to vet the xarray API is doing what it > promises by manually iterating over a set of possible indexes on its > own, and using a query operation which holds the RCU lock and then > releases it. So it is not using the helper loop options which xarray > provides on purpose. Any loop which iterates over 1 million entries > (which is possible with order 20, so emulating say a 4 GiB block size) > to just to rcu lock and unlock will eventually end up triggering a soft > lockup on systems which don't preempt, and have lock provin and RCU > prooving enabled. > > xarray users already use XA_CHECK_SCHED for loops which may take a long > time, in our case we don't want to RCU unlock and lock as the caller > does that already, but rather just force a schedule every XA_CHECK_SCHED > iterations since the test is trying to not trust and rather test that > xarray is doing the right thing. > > [0] https://lkml.kernel.org/r/202402071613.70f28243-lkp@intel.com > > Reported-by: kernel test robot <oliver.sang@intel.com> As the above links shows, this should be Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202402071613.70f28243-lkp@intel.com > --- a/lib/test_xarray.c > +++ b/lib/test_xarray.c > @@ -781,6 +781,7 @@ static noinline void *test_get_entry(struct xarray *xa, unsigned long index) > { > XA_STATE(xas, xa, index); > void *p; > + static unsigned int i = 0; I don't think this needs static storage. PetPeeve: it is unexpected that `i' has unsigned type. Can a more communicative identifier be used? I shall queue your patch as a fixup patch against test_xarray-add-tests-for-advanced-multi-index-use and shall add the below on top. Pleae check. --- a/lib/test_xarray.c~test_xarray-fix-soft-lockup-for-advanced-api-tests-fix +++ a/lib/test_xarray.c @@ -728,7 +728,7 @@ static noinline void *test_get_entry(str { XA_STATE(xas, xa, index); void *p; - static unsigned int i = 0; + unsigned int loops = 0; rcu_read_lock(); repeat: @@ -746,7 +746,7 @@ repeat: * APIs won't be stupid, proper page cache APIs loop over the proper * order so when using a larger order we skip shared entries. */ - if (++i % XA_CHECK_SCHED == 0) + if (++loops % XA_CHECK_SCHED == 0) schedule(); return p;
On Mon, Feb 19, 2024 at 06:28:08PM -0800, Andrew Morton wrote: > On Fri, 16 Feb 2024 11:43:29 -0800 Luis Chamberlain <mcgrof@kernel.org> wrote: > > > The new adanced API tests > > So this is a fix against the mm-unstable series "test_xarray: advanced > API multi-index tests", v2. Yes. > > want to vet the xarray API is doing what it > > promises by manually iterating over a set of possible indexes on its > > own, and using a query operation which holds the RCU lock and then > > releases it. So it is not using the helper loop options which xarray > > provides on purpose. Any loop which iterates over 1 million entries > > (which is possible with order 20, so emulating say a 4 GiB block size) > > to just to rcu lock and unlock will eventually end up triggering a soft > > lockup on systems which don't preempt, and have lock provin and RCU > > prooving enabled. > > > > xarray users already use XA_CHECK_SCHED for loops which may take a long > > time, in our case we don't want to RCU unlock and lock as the caller > > does that already, but rather just force a schedule every XA_CHECK_SCHED > > iterations since the test is trying to not trust and rather test that > > xarray is doing the right thing. > > > > [0] https://lkml.kernel.org/r/202402071613.70f28243-lkp@intel.com > > > > Reported-by: kernel test robot <oliver.sang@intel.com> > > As the above links shows, this should be > > Reported-by: kernel test robot <oliver.sang@intel.com> > Closes: https://lore.kernel.org/oe-lkp/202402071613.70f28243-lkp@intel.com Thanks, yes... > > --- a/lib/test_xarray.c > > +++ b/lib/test_xarray.c > > @@ -781,6 +781,7 @@ static noinline void *test_get_entry(struct xarray *xa, unsigned long index) > > { > > XA_STATE(xas, xa, index); > > void *p; > > + static unsigned int i = 0; > > I don't think this needs static storage. Actually it does, without it the schedule never happens and produces the soft lockup in the splat below.: > PetPeeve: it is unexpected that `i' has unsigned type. Can a more > communicative identifier be used? Sure, The static however is needed otherwise we end up with: Feb 20 14:37:09 small kernel: Linux version 6.8.0-rc4-next-20240212+ (mcgrof@deb-101020-bm01) (gcc (Debian 13.2.0-4) 13.2.0, GNU ld (GNU Binutils for Debian) 2.41) #23 SMP PREEMPT_DYNAMIC Tue Feb 20 14:34:35 UTC 2024 Feb 20 14:37:09 small kernel: Command line: BOOT_IMAGE=/boot/vmlinuz-6.8.0-rc4-next-20240212+ root=UUID=79e12315-47fe-462c-b69d-270b4fa13487 ro console=tty0 console=tty1 console=ttyS0,115200n8 elevator=noop scsi_mod.use_blk_mq=Y net.ifnames=0 biosdevname=0 Feb 20 14:37:09 small kernel: BIOS-provided physical RAM map: Feb 20 14:37:09 small kernel: BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable ... Feb 20 14:37:09 small kernel: Freeing initrd memory: 95720K Feb 20 14:37:09 small kernel: Block layer SCSI generic (bsg) driver version 0.4 loaded (major 248) Feb 20 14:37:09 small kernel: io scheduler mq-deadline registered ... And the soft lockup: Feb 20 14:37:09 small kernel: watchdog: BUG: soft lockup - CPU#0 stuck for 26s! [swapper/0:1] Feb 20 14:37:09 small kernel: Modules linked in: Feb 20 14:37:09 small kernel: irq event stamp: 1786208 Feb 20 14:37:09 small kernel: hardirqs last enabled at (1786207): [<ffffffff839633c4>] _raw_spin_unlock_irq+0x24/0x50 Feb 20 14:37:09 small kernel: hardirqs last disabled at (1786208): [<ffffffff8394aafa>] sysvec_apic_timer_interrupt+0xa/0xc0 Feb 20 14:37:09 small kernel: softirqs last enabled at (1786198): [<ffffffff82e96746>] __irq_exit_rcu+0x76/0xd0 Feb 20 14:37:09 small kernel: softirqs last disabled at (1786193): [<ffffffff82e96746>] __irq_exit_rcu+0x76/0xd0 Feb 20 14:37:09 small kernel: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.8.0-rc4-next-20240212+ #23 Feb 20 14:37:09 small kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Feb 20 14:37:09 small kernel: RIP: 0010:lock_is_held_type+0xee/0x120 Feb 20 14:37:09 small kernel: Code: 77 da f2 83 e8 83 0b 00 00 b8 ff ff ff ff 65 0f c1 05 6e 21 6d 7c 83 f8 01 75 20 41 f7 c7 00 02 00 00 74 06 fb 0f 1f 44 00 00 <5b> 89 e8 5d 41 5c 41 5d 41 5e 41 5f c3 31 ed eb c2 0f 0b 48 c7 c7 Feb 20 14:37:09 small kernel: RSP: 0000:ffffbf4400017d48 EFLAGS: 00000206 Feb 20 14:37:09 small kernel: RAX: 0000000000000001 RBX: ffff9bfe4180ce98 RCX: 0000000000000001 Feb 20 14:37:09 small kernel: RDX: 0000000000000000 RSI: ffffffff83f2da77 RDI: ffffffff83f5c6bf Feb 20 14:37:09 small kernel: RBP: 0000000000000000 R08: 0000000000000019 R09: 0000000000000019 Feb 20 14:37:09 small kernel: R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff84355b38 Feb 20 14:37:09 small kernel: R13: ffff9bfe4180c400 R14: 00000000ffffffff R15: 0000000000000246 Feb 20 14:37:09 small kernel: FS: 0000000000000000(0000) GS:ffff9bfebdc00000(0000) knlGS:0000000000000000 Feb 20 14:37:09 small kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Feb 20 14:37:09 small kernel: CR2: ffff9bfe53601000 CR3: 0000000011e23001 CR4: 0000000000770ef0 Feb 20 14:37:09 small kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 Feb 20 14:37:09 small kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Feb 20 14:37:09 small kernel: PKRU: 55555554 Feb 20 14:37:09 small kernel: Call Trace: Feb 20 14:37:09 small kernel: <IRQ> Feb 20 14:37:09 small kernel: ? watchdog_timer_fn+0x271/0x310 Feb 20 14:37:09 small kernel: ? softlockup_fn+0x70/0x70 Feb 20 14:37:09 small kernel: ? __hrtimer_run_queues+0x19e/0x360 Feb 20 14:37:09 small kernel: ? hrtimer_interrupt+0xfe/0x230 Feb 20 14:37:09 small kernel: ? __sysvec_apic_timer_interrupt+0x84/0x1d0 Feb 20 14:37:09 small kernel: ? sysvec_apic_timer_interrupt+0x98/0xc0 Feb 20 14:37:09 small kernel: </IRQ> Feb 20 14:37:09 small kernel: <TASK> Feb 20 14:37:09 small kernel: ? asm_sysvec_apic_timer_interrupt+0x16/0x20 Feb 20 14:37:09 small kernel: ? lock_is_held_type+0xee/0x120 Feb 20 14:37:09 small kernel: ? lock_is_held_type+0xcd/0x120 Feb 20 14:37:09 small kernel: xas_descend+0xc9/0x190 Feb 20 14:37:09 small kernel: xas_load+0x39/0x50 Feb 20 14:37:09 small kernel: test_get_entry.constprop.0+0x91/0x170 Feb 20 14:37:09 small kernel: check_xa_multi_store_adv.constprop.0+0x21c/0x4c0 Feb 20 14:37:09 small kernel: check_multi_store_advanced.constprop.0+0x3a/0x60 Feb 20 14:37:09 small kernel: ? check_xas_retry.constprop.0+0x9a0/0x9a0 Feb 20 14:37:09 small kernel: xarray_checks+0x4f/0xe0 Feb 20 14:37:09 small kernel: do_one_initcall+0x5d/0x350 Feb 20 14:37:09 small kernel: kernel_init_freeable+0x24d/0x410 Feb 20 14:37:09 small kernel: ? rest_init+0x190/0x190 Feb 20 14:37:09 small kernel: kernel_init+0x16/0x1b0 Feb 20 14:37:09 small kernel: ret_from_fork+0x2d/0x50 Feb 20 14:37:09 small kernel: ? rest_init+0x190/0x190 Feb 20 14:37:09 small kernel: ret_from_fork_asm+0x11/0x20 Feb 20 14:37:09 small kernel: </TASK> Feb 20 14:37:09 small kernel: watchdog: BUG: soft lockup - CPU#0 stuck for 52s! [swapper/0:1] Feb 20 14:37:09 small kernel: Modules linked in: Feb 20 14:37:09 small kernel: irq event stamp: 1838538 Feb 20 14:37:09 small kernel: hardirqs last enabled at (1838537): [<ffffffff83a00d06>] asm_sysvec_apic_timer_interrupt+0x16/0x20 Feb 20 14:37:09 small kernel: hardirqs last disabled at (1838538): [<ffffffff8394aafa>] sysvec_apic_timer_interrupt+0xa/0xc0 Feb 20 14:37:09 small kernel: softirqs last enabled at (1838508): [<ffffffff82e96746>] __irq_exit_rcu+0x76/0xd0 Feb 20 14:37:09 small kernel: softirqs last disabled at (1838503): [<ffffffff82e96746>] __irq_exit_rcu+0x76/0xd0 Feb 20 14:37:09 small kernel: CPU: 0 PID: 1 Comm: swapper/0 Tainted: G L 6.8.0-rc4-next-20240212+ #23 Feb 20 14:37:09 small kernel: Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014 Feb 20 14:37:09 small kernel: RIP: 0010:lock_is_held_type+0xee/0x120 Feb 20 14:37:09 small kernel: Code: 77 da f2 83 e8 83 0b 00 00 b8 ff ff ff ff 65 0f c1 05 6e 21 6d 7c 83 f8 01 75 20 41 f7 c7 00 02 00 00 74 06 fb 0f 1f 44 00 00 <5b> 89 e8 5d 41 5c 41 5d 41 5e 41 5f c3 31 ed eb c2 0f 0b 48 c7 c7 Feb 20 14:37:09 small kernel: RSP: 0000:ffffbf4400017d48 EFLAGS: 00000206 Feb 20 14:37:09 small kernel: RAX: 0000000000000001 RBX: ffff9bfe4180ce70 RCX: 0000000000000001 Feb 20 14:37:09 small kernel: RDX: 0000000000000000 RSI: ffffffff83f2da77 RDI: ffffffff83f5c6bf Feb 20 14:37:09 small kernel: RBP: 0000000000000001 R08: 0000000000000019 R09: 0000000000000019 Feb 20 14:37:09 small kernel: R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff842d1040 Feb 20 14:37:09 small kernel: R13: ffff9bfe4180c400 R14: 00000000ffffffff R15: 0000000000000246 Feb 20 14:37:09 small kernel: FS: 0000000000000000(0000) GS:ffff9bfebdc00000(0000) knlGS:0000000000000000 Feb 20 14:37:09 small kernel: CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 Feb 20 14:37:09 small kernel: CR2: ffff9bfe53601000 CR3: 0000000011e23001 CR4: 0000000000770ef0 Feb 20 14:37:09 small kernel: DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 Feb 20 14:37:09 small kernel: DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Feb 20 14:37:09 small kernel: PKRU: 55555554 Feb 20 14:37:09 small kernel: Call Trace: Feb 20 14:37:09 small kernel: <IRQ> Feb 20 14:37:09 small kernel: ? watchdog_timer_fn+0x271/0x310 Feb 20 14:37:09 small kernel: ? softlockup_fn+0x70/0x70 Feb 20 14:37:09 small kernel: ? __hrtimer_run_queues+0x19e/0x360 Feb 20 14:37:09 small kernel: ? hrtimer_interrupt+0xfe/0x230 Feb 20 14:37:09 small kernel: ? __sysvec_apic_timer_interrupt+0x84/0x1d0 Feb 20 14:37:09 small kernel: ? sysvec_apic_timer_interrupt+0x98/0xc0 Feb 20 14:37:09 small kernel: </IRQ> Feb 20 14:37:09 small kernel: <TASK> Feb 20 14:37:09 small kernel: ? asm_sysvec_apic_timer_interrupt+0x16/0x20 Feb 20 14:37:09 small kernel: ? lock_is_held_type+0xee/0x120 Feb 20 14:37:09 small kernel: ? lock_is_held_type+0xcd/0x120 Feb 20 14:37:09 small kernel: xas_descend+0xd6/0x190 Feb 20 14:37:09 small kernel: xas_load+0x39/0x50 Feb 20 14:37:09 small kernel: test_get_entry.constprop.0+0x91/0x170 Feb 20 14:37:09 small kernel: check_xa_multi_store_adv.constprop.0+0x3b1/0x4c0 Feb 20 14:37:09 small kernel: check_multi_store_advanced.constprop.0+0x3a/0x60 Feb 20 14:37:09 small kernel: ? check_xas_retry.constprop.0+0x9a0/0x9a0 Feb 20 14:37:09 small kernel: xarray_checks+0x4f/0xe0 Feb 20 14:37:09 small kernel: do_one_initcall+0x5d/0x350 Feb 20 14:37:09 small kernel: kernel_init_freeable+0x24d/0x410 Feb 20 14:37:09 small kernel: ? rest_init+0x190/0x190 Feb 20 14:37:09 small kernel: kernel_init+0x16/0x1b0 Feb 20 14:37:09 small kernel: ret_from_fork+0x2d/0x50 Feb 20 14:37:09 small kernel: ? rest_init+0x190/0x190 Feb 20 14:37:09 small kernel: ret_from_fork_asm+0x11/0x20 Feb 20 14:37:09 small kernel: </TASK> Feb 20 14:37:09 small kernel: XArray: 148257077 of 148257077 tests passed Luis
On Tue, 20 Feb 2024 09:45:19 -0800 Luis Chamberlain <mcgrof@kernel.org> wrote: > > > --- a/lib/test_xarray.c > > > +++ b/lib/test_xarray.c > > > @@ -781,6 +781,7 @@ static noinline void *test_get_entry(struct xarray *xa, unsigned long index) > > > { > > > XA_STATE(xas, xa, index); > > > void *p; > > > + static unsigned int i = 0; > > > > I don't think this needs static storage. > > Actually it does, without it the schedule never happens and produces the > soft lockup in the splat below.: OK, I'll restore that.
diff --git a/lib/test_xarray.c b/lib/test_xarray.c index d4e55b4867dc..ac162025cc59 100644 --- a/lib/test_xarray.c +++ b/lib/test_xarray.c @@ -781,6 +781,7 @@ static noinline void *test_get_entry(struct xarray *xa, unsigned long index) { XA_STATE(xas, xa, index); void *p; + static unsigned int i = 0; rcu_read_lock(); repeat: @@ -790,6 +791,17 @@ static noinline void *test_get_entry(struct xarray *xa, unsigned long index) goto repeat; rcu_read_unlock(); + /* + * This is not part of the page cache, this selftest is pretty + * aggressive and does not want to trust the xarray API but rather + * test it, and for order 20 (4 GiB block size) we can loop over + * over a million entries which can cause a soft lockup. Page cache + * APIs won't be stupid, proper page cache APIs loop over the proper + * order so when using a larger order we skip shared entries. + */ + if (++i % XA_CHECK_SCHED == 0) + schedule(); + return p; }
The new adanced API tests want to vet the xarray API is doing what it promises by manually iterating over a set of possible indexes on its own, and using a query operation which holds the RCU lock and then releases it. So it is not using the helper loop options which xarray provides on purpose. Any loop which iterates over 1 million entries (which is possible with order 20, so emulating say a 4 GiB block size) to just to rcu lock and unlock will eventually end up triggering a soft lockup on systems which don't preempt, and have lock provin and RCU prooving enabled. xarray users already use XA_CHECK_SCHED for loops which may take a long time, in our case we don't want to RCU unlock and lock as the caller does that already, but rather just force a schedule every XA_CHECK_SCHED iterations since the test is trying to not trust and rather test that xarray is doing the right thing. [0] https://lkml.kernel.org/r/202402071613.70f28243-lkp@intel.com Reported-by: kernel test robot <oliver.sang@intel.com> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> --- lib/test_xarray.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)