09cffecaa7
Function show_regs() is usually called in interrupt handler or exception handler, it prints the registers specified by the parameter 'regs', then dump the stack traces. Although not explicitly documented, dump the stack traces based on'regs' seems to make the most sense. Although dump_stack() can finally dump the desired content, because 'regs' are saved by the entry of current interrupt or exception. In the following example we can see: 1) The backtrace of interrupt or exception handler is not expected, it causes confusion. 2) Something is printed repeatedly. The line with the kernel version "CPU: 0 PID: 70 Comm: test0 Not tainted 5.19.0+ #8", the registers saved in "Exception stack" which 'regs' actually point to. For example: rcu: INFO: rcu_sched self-detected stall on CPU rcu: 0-....: (499 ticks this GP) idle=379/1/0x40000002 softirq=91/91 fqs=249 (t=500 jiffies g=-911 q=13 ncpus=4) CPU: 0 PID: 70 Comm: test0 Not tainted 5.19.0+ #8 Hardware name: ARM-Versatile Express PC is at ktime_get+0x4c/0xe8 LR is at ktime_get+0x4c/0xe8 pc : 8019a474 lr : 8019a474 psr: 60000013 sp : cabd1f28 ip : 00000001 fp : 00000005 r10: 527bf1b8 r9 : 431bde82 r8 : d7b634db r7 : 0000156e r6 : 61f234f8 r5 : 00000001 r4 : 80ca86c0 r3 : ffffffff r2 : fe5bce0b r1 : 00000000 r0 : 01a431f4 Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 6121406a DAC: 00000051 CPU: 0 PID: 70 Comm: test0 Not tainted 5.19.0+ #8 <-----------start---------- Hardware name: ARM-Versatile Express | unwind_backtrace from show_stack+0x10/0x14 | show_stack from dump_stack_lvl+0x40/0x4c | dump_stack_lvl from rcu_dump_cpu_stacks+0x10c/0x134 | rcu_dump_cpu_stacks from rcu_sched_clock_irq+0x780/0xaf4 | rcu_sched_clock_irq from update_process_times+0x54/0x74 | update_process_times from tick_periodic+0x3c/0xd4 | tick_periodic from tick_handle_periodic+0x20/0x80 worthless tick_handle_periodic from twd_handler+0x30/0x40 or twd_handler from handle_percpu_devid_irq+0x8c/0x1c8 duplicated handle_percpu_devid_irq from generic_handle_domain_irq+0x24/0x34 | generic_handle_domain_irq from gic_handle_irq+0x74/0x88 | gic_handle_irq from generic_handle_arch_irq+0x34/0x44 | generic_handle_arch_irq from call_with_stack+0x18/0x20 | call_with_stack from __irq_svc+0x98/0xb0 | Exception stack(0xcabd1ed8 to 0xcabd1f20) | 1ec0: 01a431f4 00000000 | 1ee0: fe5bce0b ffffffff 80ca86c0 00000001 61f234f8 0000156e d7b634db 431bde82 | 1f00: 527bf1b8 00000005 00000001 cabd1f28 8019a474 8019a474 60000013 ffffffff | __irq_svc from ktime_get+0x4c/0xe8 <---------end-------------- ktime_get from test_task+0x44/0x110 test_task from kthread+0xd8/0xf4 kthread from ret_from_fork+0x14/0x2c Exception stack(0xcabd1fb0 to 0xcabd1ff8) 1fa0: 00000000 00000000 00000000 00000000 1fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 1fe0: 00000000 00000000 00000000 00000000 00000013 00000000 After replacing dump_stack() with dump_backtrace(): rcu: INFO: rcu_sched self-detected stall on CPU rcu: 0-....: (500 ticks this GP) idle=8f7/1/0x40000002 softirq=129/129 fqs=241 (t=500 jiffies g=-915 q=13 ncpus=4) CPU: 0 PID: 69 Comm: test0 Not tainted 5.19.0+ #9 Hardware name: ARM-Versatile Express PC is at ktime_get+0x4c/0xe8 LR is at ktime_get+0x4c/0xe8 pc : 8019a494 lr : 8019a494 psr: 60000013 sp : cabddf28 ip : 00000001 fp : 00000002 r10: 0779cb48 r9 : 431bde82 r8 : d7b634db r7 : 00000a66 r6 : e835ab70 r5 : 00000001 r4 : 80ca86c0 r3 : ffffffff r2 : ff337d39 r1 : 00000000 r0 : 00cc82c6 Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 611d006a DAC: 00000051 ktime_get from test_task+0x44/0x110 test_task from kthread+0xd8/0xf4 kthread from ret_from_fork+0x14/0x2c Exception stack(0xcabddfb0 to 0xcabddff8) dfa0: 00000000 00000000 00000000 00000000 dfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 dfe0: 00000000 00000000 00000000 00000000 00000013 00000000 Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| 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 | ||
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.