26d1982fd1
The commit 55d6af1d66885059ffc2a ("lib/nmi_backtrace: explicitly serialize
banner and regs") serialized backtraces from more CPUs using the re-entrant
printk_printk_cpu lock. It was a preparation step for removing the obsolete
nmi_safe buffers.
The single-line messages about idle CPUs were not serialized against other
CPUs and might appear in the middle of backtrace from another CPU,
for example:
[56394.590068] NMI backtrace for cpu 2
[56394.590069] CPU: 2 PID: 444 Comm: systemd-journal Not tainted 5.14.0-rc1-default+ #268
[56394.590071] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.12.0-59-gc9ba527-rebuilt.opensuse.org 04/01/2014
[56394.590072] RIP: 0010:lock_is_held_type+0x0/0x120
[56394.590071] NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0xb/0x10
[56394.590076] Code: a2 38 ff 0f 0b 8b 44 24 04 eb bd 48 8d ...
[56394.590077] RSP: 0018:ffffab02c07c7e68 EFLAGS: 00000246
[56394.590079] RAX: 0000000000000000 RBX: ffff9a7bc0ec8a40 RCX: ffffffffaab8eb40
It might cause confusion what CPU the following lines belongs to and
whether the backtraces are really serialized.
Prevent the confusion and serialize also the single line message against
other CPUs.
Fixes: 55d6af1d66885059ffc2a ("lib/nmi_backtrace: explicitly serialize banner and regs")
Reviewed-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20210727080939.27193-1-pmladek@suse.com
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.