CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT: Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)

General informations

The Linux kernel configuration item CONFIG_PRINTK_SAFE_LOG_BUF_SHIFT:

• prompt: Temporary per-CPU printk log buffer size (12 => 4KB, 13 => 8KB)
• type: int
• depends on: CONFIG_PRINTK
• defined in init/Kconfig
• found in Linux kernels: 4.11–4.20, 5.0–5.19, 6.0–6.3

Help text

Select the size of an alternate printk per-CPU buffer where messages printed from unsafe contexts are temporary stored. One example would be NMI messages, another one - printk recursion. The messages are copied to the main log buffer in a safe context to avoid a deadlock. The value defines the size as a power of 2.

Those messages are rare and limited. The largest one is when a backtrace is printed. It usually fits into 4KB. Select 8KB if you want to be on the safe side.

Examples: 17 => 128 KB for each CPU 16 => 64 KB for each CPU 15 => 32 KB for each CPU 14 => 16 KB for each CPU 13 => 8 KB for each CPU 12 => 4 KB for each CPU

Hardware

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Sources

This page is automaticly generated with free (libre, open) software lkddb(see lkddb-sources).

The data is retrived from:

• Linux kernel
• Linux Kernel Driver DataBase (LKDDb)

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