fee13fe965
The btrfs zstd workspace manager uses a background timer to reclaim not
recently used workspaces. I used spin_lock() from this context which
should have been caught with lockdep, but was not. This deadlock was
reported in bugzilla. The fix is to switch the zstd wsm lock to use
spin_lock_bh() from the softirq context.
This happened quite relibably on ppc64, unlike on other architectures.
[ 313.402874] ================================
[ 313.402875] WARNING: inconsistent lock state
[ 313.402879] 5.1.0-rc7 #1 Not tainted
[ 313.402880] --------------------------------
[ 313.402882] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
[ 313.402885] swapper/5/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
[ 313.402888] 0000000080d1120c (&(&wsm.lock)->rlock){+.?.}, at: .zstd_reclaim_timer_fn+0x40/0x230
[ 313.402895] {SOFTIRQ-ON-W} state was registered at:
[ 313.402899] .lock_acquire+0xd0/0x240
[ 313.402903] ._raw_spin_lock+0x34/0x60
[ 313.402906] .zstd_get_workspace+0xd0/0x360
[ 313.402908] .end_compressed_bio_read+0x3b8/0x540
[ 313.402911] .bio_endio+0x174/0x2c0
[ 313.402914] .end_workqueue_fn+0x4c/0x70
[ 313.402917] .normal_work_helper+0x138/0x7e0
[ 313.402920] .process_one_work+0x324/0x790
[ 313.402922] .worker_thread+0x68/0x570
[ 313.402925] .kthread+0x19c/0x1b0
[ 313.402928] .ret_from_kernel_thread+0x58/0x78
[ 313.402930] irq event stamp: 2629216
[ 313.402933] hardirqs last enabled at (2629216): [<c0000000009da738>] ._raw_spin_unlock_irq+0x38/0x60
[ 313.402936] hardirqs last disabled at (2629215): [<c0000000009da4c4>] ._raw_spin_lock_irq+0x24/0x70
[ 313.402939] softirqs last enabled at (2629212): [<c0000000000af9fc>] .irq_enter+0x8c/0xd0
[ 313.402942] softirqs last disabled at (2629213): [<c0000000000afb58>] .irq_exit+0x118/0x170
[ 313.402944]
other info that might help us debug this:
[ 313.402945] Possible unsafe locking scenario:
[ 313.402947] CPU0
[ 313.402948] ----
[ 313.402949] lock(&(&wsm.lock)->rlock);
[ 313.402951] <Interrupt>
[ 313.402952] lock(&(&wsm.lock)->rlock);
[ 313.402954]
*** DEADLOCK ***
[ 313.402957] 1 lock held by swapper/5/0:
[ 313.402958] #0: 000000004b612042 ((&wsm.timer)){+.-.}, at: .call_timer_fn+0x0/0x3c0
[ 313.402963]
stack backtrace:
[ 313.402967] CPU: 5 PID: 0 Comm: swapper/5 Not tainted 5.1.0-rc7 #1
[ 313.402968] Call Trace:
[ 313.402972] [c0000007fa262e70] [c0000000009b3294] .dump_stack+0xe0/0x15c (unreliable)
[ 313.402975] [c0000007fa262f10] [c000000000125548] .print_usage_bug+0x348/0x390
[ 313.402978] [c0000007fa262fd0] [c000000000125cb4] .mark_lock+0x724/0x930
[ 313.402981] [c0000007fa263080] [c000000000126c20] .__lock_acquire+0xc90/0x16a0
[ 313.402984] [c0000007fa2631b0] [c000000000128040] .lock_acquire+0xd0/0x240
[ 313.402987] [c0000007fa263280] [c0000000009da2b4] ._raw_spin_lock+0x34/0x60
[ 313.402990] [c0000007fa263300] [c00000000054b0b0] .zstd_reclaim_timer_fn+0x40/0x230
[ 313.402993] [c0000007fa2633d0] [c000000000158b38] .call_timer_fn+0xc8/0x3c0
[ 313.402996] [c0000007fa2634a0] [c000000000158f74] .expire_timers+0x144/0x260
[ 313.402999] [c0000007fa263550] [c000000000159178] .run_timer_softirq+0xe8/0x230
[ 313.403002] [c0000007fa263680] [c0000000009db288] .__do_softirq+0x188/0x5d4
[ 313.403004] [c0000007fa263790] [c0000000000afb58] .irq_exit+0x118/0x170
[ 313.403008] [c0000007fa263800] [c000000000028d88] .timer_interrupt+0x158/0x430
[ 313.403012] [c0000007fa2638b0] [c0000000000091d4] decrementer_common+0x134/0x140
[ 313.403017] --- interrupt: 901 at replay_interrupt_return+0x0/0x4
LR = .arch_local_irq_restore.part.0+0x68/0x80
[ 313.403020] [c0000007fa263bb0] [c00000000001a3ac] .arch_local_irq_restore.part.0+0x2c/0x80 (unreliable)
[ 313.403024] [c0000007fa263c30] [c0000000007bbbcc] .cpuidle_enter_state+0xec/0x670
[ 313.403027] [c0000007fa263d00] [c0000000000f5130] .call_cpuidle+0x40/0x90
[ 313.403031] [c0000007fa263d70] [c0000000000f554c] .do_idle+0x2dc/0x3a0
[ 313.403034] [c0000007fa263e30] [c0000000000f59ac] .cpu_startup_entry+0x2c/0x30
[ 313.403037] [c0000007fa263ea0] [c000000000045674] .start_secondary+0x644/0x650
[ 313.403041] [c0000007fa263f90] [c00000000000ad5c] start_secondary_prolog+0x10/0x14
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=203517
Fixes:
|
||
|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.