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Date: Mon, 18 Sep 2023 07:47:04 +0200
From: Tomas Glozar <tglozar@...hat.com>
To: Ira Weiny <ira.weiny@...el.com>
Cc: Tomáš Glozar <tglozar@...il.com>,
nvdimm@...ts.linux.dev, dan.j.williams@...el.com,
vishal.l.verma@...el.com, dave.jiang@...el.com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] nd_btt: Make BTT lanes preemptible
čt 14. 9. 2023 v 22:18 odesílatel Ira Weiny <ira.weiny@...el.com> napsal:
> Is the bug in 1 of 2 places?
>
> 1) When btt_write_pg()->lock_map() (when the number of lanes is < number
> of cpus) and the lane is acquired is called?
>
> *or*
>
> 2) When nd_region_acquire_lane() internally trys to take it's lock?
>
> A copy/paste of the BUG observed would have been more clear I think.
>
The BUG was observed on btt_write_pg()->lock_map(), but I assume the
BUG will also happen on the lock in nd_region_acquire_lane, since that
is also a spin lock, i.e. a sleeping lock on RT.
BUG observed in dmesg when running ndctl tests on RT kernel without the patch:
[ 123.262740] nfit_test_iomap: loading out-of-tree module taints kernel.
[ 123.262744] nfit_test_iomap: loading test module taints kernel.
[ 123.408628] nfit_test nfit_test.0: changing numa node from -1 to 0
for nfit region [0x0000000100000000-0x0000000101ffffff]
[ 123.408633] nfit_test nfit_test.0: changing target node from -1 to
0 for nfit region [0x0000000100000000-0x0000000101ffffff]
[ 123.408852] nfit_test nfit_test.0: changing numa node from -1 to 0
for nfit region [0x0000000108000000-0x000000010bffffff]
[ 123.408855] nfit_test nfit_test.0: changing target node from -1 to
0 for nfit region [0x0000000108000000-0x000000010bffffff]
[ 123.408933] nfit_test nfit_test.0: changing numa node from -1 to 0
for nfit region [0xffffb900c2cbd000-0xffffb900c2cbd00b]
[ 123.408935] nfit_test nfit_test.0: changing target node from -1 to
0 for nfit region [0xffffb900c2cbd000-0xffffb900c2cbd00b]
[ 123.408961] nfit_test nfit_test.0: changing numa node from -1 to 0
for nfit region [0xffffb900c2cde000-0xffffb900c2cde00b]
[ 123.408963] nfit_test nfit_test.0: changing target node from -1 to
0 for nfit region [0xffffb900c2cde000-0xffffb900c2cde00b]
[ 123.408988] nfit_test nfit_test.0: changing numa node from -1 to 0
for nfit region [0xffffb900c2cff000-0xffffb900c2cff00b]
[ 123.408990] nfit_test nfit_test.0: changing target node from -1 to
0 for nfit region [0xffffb900c2cff000-0xffffb900c2cff00b]
[ 123.409015] nfit_test nfit_test.0: changing numa node from -1 to 0
for nfit region [0xffffb900c2d45000-0xffffb900c2d4500b]
[ 123.409018] nfit_test nfit_test.0: changing target node from -1 to
0 for nfit region [0xffffb900c2d45000-0xffffb900c2d4500b]
[ 123.409586] nfit_test nfit_test.0: failed to evaluate _FIT
[ 123.441834] nfit_test nfit_test.1: Error found in NVDIMM nmem4
flags: save_fail restore_fail flush_fail not_armed
[ 123.441857] nfit_test nfit_test.1: Error found in NVDIMM nmem5
flags: map_fail
[ 123.457346] nfit_test nfit_test.1: changing numa node from -1 to 0
for nfit region [0x0000000140000000-0x0000000141ffffff]
[ 123.457351] nfit_test nfit_test.1: changing target node from -1 to
0 for nfit region [0x0000000140000000-0x0000000141ffffff]
[ 123.457427] nfit_test nfit_test.1: changing numa node from -1 to 0
for nfit region [0xffffb900c361d000-0xffffb900c3a1cfff]
[ 123.457429] nfit_test nfit_test.1: changing target node from -1 to
0 for nfit region [0xffffb900c361d000-0xffffb900c3a1cfff]
[ 123.475513] nd_pmem namespace3.0: unable to guarantee persistence of writes
[ 123.484778] nd_pmem namespace2.0: region2 read-only, marking pmem2 read-only
[ 126.349866] nd_pmem btt0.0: No existing arenas
[ 126.407070] BUG: sleeping function called from invalid context at
kernel/locking/spinlock_rt.c:48
[ 126.407073] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid:
4903, name: libndctl
[ 126.407074] preempt_count: 1, expected: 0
[ 126.407075] RCU nest depth: 0, expected: 0
[ 126.407075] 1 lock held by libndctl/4903:
[ 126.407076] #0: ffff8c184a270060
(&arena->map_locks[i].lock){+.+.}-{2:2}, at: btt_write_pg+0x2d7/0x500
[nd_btt]
[ 126.407085] Preemption disabled at:
[ 126.407085] [<ffffffffc1313db5>] nd_region_acquire_lane+0x15/0x90 [libnvdimm]
[ 126.407099] CPU: 1 PID: 4903 Comm: libndctl Kdump: loaded Tainted:
G W O N------- ---
6.5.0-ark.ndctl-tests.el9+rt-debug-rt6+ #6
[ 126.407101] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009),
BIOS 1.16.2-1.fc38 04/01/2014
[ 126.407102] Call Trace:
[ 126.407103] <TASK>
[ 126.407104] dump_stack_lvl+0x8e/0xb0
[ 126.407109] __might_resched+0x19b/0x250
[ 126.407113] rt_spin_lock+0x4c/0x100
[ 126.407116] ? btt_write_pg+0x2d7/0x500 [nd_btt]
[ 126.407120] btt_write_pg+0x2d7/0x500 [nd_btt]
[ 126.407127] ? local_clock_noinstr+0x9/0xc0
[ 126.407131] btt_submit_bio+0x16d/0x270 [nd_btt]
[ 126.407138] __submit_bio+0x48/0x80
[ 126.407141] __submit_bio_noacct+0x7e/0x1e0
[ 126.407146] submit_bio_wait+0x58/0xb0
[ 126.407153] __blkdev_direct_IO_simple+0x107/0x240
[ 126.407156] ? inode_set_ctime_current+0x51/0x110
[ 126.407164] ? __pfx_submit_bio_wait_endio+0x10/0x10
[ 126.407171] blkdev_write_iter+0x1d8/0x290
[ 126.407174] vfs_write+0x237/0x330
[ 126.407183] ksys_write+0x68/0xf0
[ 126.407187] do_syscall_64+0x59/0x90
[ 126.407192] ? do_syscall_64+0x69/0x90
[ 126.407193] ? lockdep_hardirqs_on+0x79/0x100
[ 126.407195] ? do_syscall_64+0x69/0x90
[ 126.407196] ? lockdep_hardirqs_on+0x79/0x100
[ 126.407198] ? do_syscall_64+0x69/0x90
[ 126.407199] ? do_syscall_64+0x69/0x90
[ 126.407200] ? lockdep_hardirqs_on+0x79/0x100
[ 126.407202] entry_SYSCALL_64_after_hwframe+0x6e/0xd8
[ 126.407205] RIP: 0033:0x7f95f2f3eba7
[ 126.407218] Code: 0b 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7
0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00
00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89
7
4 24
[ 126.407219] RSP: 002b:00007ffe7a298678 EFLAGS: 00000246 ORIG_RAX:
0000000000000001
[ 126.407221] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f95f2f3eba7
[ 126.407222] RDX: 0000000000001000 RSI: 0000000001ea9000 RDI: 000000000000000a
[ 126.407223] RBP: 00007ffe7a298740 R08: 0000000000000000 R09: 00007f95f2fb14e0
[ 126.407223] R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffe7a298be8
[ 126.407224] R13: 000000000040e3a2 R14: 0000000000412db8 R15: 00007f95f31ff000
[ 126.407233] </TASK>
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