Linux kernel source tree
01ef7ff7dd
The delayed work item function nvmet_pci_epf_poll_sqs_work() polls all
submission queues and keeps running in a loop as long as commands are
being submitted by the host. Depending on the preemption configuration
of the kernel, under heavy command workload, this function can thus run
for more than RCU_CPU_STALL_TIMEOUT seconds, leading to a RCU stall:
rcu: INFO: rcu_sched self-detected stall on CPU
rcu: 5-....: (20998 ticks this GP) idle=4244/1/0x4000000000000000 softirq=301/301 fqs=5132
rcu: (t=21000 jiffies g=-443 q=12 ncpus=8)
CPU: 5 UID: 0 PID: 82 Comm: kworker/5:1 Not tainted 6.14.0-rc2 #1
Hardware name: Radxa ROCK 5B (DT)
Workqueue: events nvmet_pci_epf_poll_sqs_work [nvmet_pci_epf]
pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : dw_edma_device_tx_status+0xb8/0x130
lr : dw_edma_device_tx_status+0x9c/0x130
sp : ffff800080b5bbb0
x29: ffff800080b5bbb0 x28: ffff0331c5c78400 x27: ffff0331c1cd1960
x26: ffff0331c0e39010 x25: ffff0331c20e4000 x24: ffff0331c20e4a90
x23: 0000000000000000 x22: 0000000000000001 x21: 00000000005aca33
x20: ffff800080b5bc30 x19: ffff0331c123e370 x18: 000000000ab29e62
x17: ffffb2a878c9c118 x16: ffff0335bde82040 x15: 0000000000000000
x14: 000000000000017b x13: 00000000ee601780 x12: 0000000000000018
x11: 0000000000000000 x10: 0000000000000001 x9 : 0000000000000040
x8 : 00000000ee601780 x7 : 0000000105c785c0 x6 : ffff0331c1027d80
x5 : 0000000001ee7ad6 x4 : ffff0335bdea16c0 x3 : ffff0331c123e438
x2 : 00000000005aca33 x1 : 0000000000000000 x0 : ffff0331c123e410
Call trace:
dw_edma_device_tx_status+0xb8/0x130 (P)
dma_sync_wait+0x60/0xbc
nvmet_pci_epf_dma_transfer+0x128/0x264 [nvmet_pci_epf]
nvmet_pci_epf_poll_sqs_work+0x2a0/0x2e0 [nvmet_pci_epf]
process_one_work+0x144/0x390
worker_thread+0x27c/0x458
kthread+0xe8/0x19c
ret_from_fork+0x10/0x20
The solution for this is simply to explicitly allow rescheduling using
cond_resched(). However, since doing so for every loop of
nvmet_pci_epf_poll_sqs_work() significantly degrades performance
(for 4K random reads using 4 I/O queues, the maximum IOPS goes down from
137 KIOPS to 110 KIOPS), call cond_resched() every second to avoid the
RCU stalls.
Fixes:
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||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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 reStructuredText 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.