Re: [PATCH V2] docs: panic: Disclaimer about console verbosity when using panic_print with pstore

[Bradley Morgan]

On 19 August 2026 19:31:30 BST, "Guilherme G. Piccoli"
<gpiccoli@xxxxxxxxxx> wrote:
>Users of panic_print / panic_sys_info are usually aware of the potentially
>huge amount of information displayed with such options - their goal by
>using them is indeed to dump more information during panic!
>
>What might come unnoticed at first is the impact that the
>console_verbose()
>call on panic path has, specially in cases that users rely on pstore as
>a means to collect the panic logs. Recent experience shows that dumping
>all tasks in an ARM64 system (with qcom_geni tty driver) gets a 2 minute
>delay on panic time due to writing such information to console. But in
>that case, pstore was used, so there was no need for console printing,
>and suppressing that reduced the full time to less than 0.5 second.
>
>The option "printk.console_no_auto_verbose" aims exactly at this use
>case: avoid automatically increasing the loglevel during panic path.
>So, let's officially document this to avoid users wasting their time
>either on long panic printing or debugging the panic delays.
>
>While at it, improve the readability of the panic_print text, by
>adding some line breaks.

I love this commit description 

>
>Suggested-by: Petr Mladek <pmladek@xxxxxxxx>
>Reviewed-by: Bradley Morgan <include@xxxxxxxxx>
>Reviewed-by: Feng Tang <feng.tang@xxxxxxxxxxxxxxxxx>
>Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx>
>---
>
>
>V2:
>- Added line breaks as per Petr's suggestion (with some text improvements
>  as well) - thanks Petr!
>
>- Added review tags - thanks Feng Tang and Bradley, feel free to check
>  again given we added the line breaks, etc.
>
>V1 link:
>https://lore.kernel.org/r/20260805205026.1699568-1-gpiccoli@xxxxxxxxxx/
>
>
> .../admin-guide/kernel-parameters.txt         | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
>diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>index deae852f71e4..51cdf4e41c21 100644
>--- a/Documentation/admin-guide/kernel-parameters.txt
>+++ b/Documentation/admin-guide/kernel-parameters.txt
>@@ -4874,6 +4874,7 @@ Kernel parameters
> 
> 	panic_print=	Bitmask for printing system info when panic happens.
> 			User can chose combination of the following bits:
>+
> 			bit 0: print all tasks info
> 			bit 1: print system memory info
> 			bit 2: print timer info
>@@ -4882,10 +4883,16 @@ Kernel parameters
> 			bit 5: replay all kernel messages on consoles at the end of panic
> 			bit 6: print all CPUs backtrace (if available in the arch)
> 			bit 7: print only tasks in uninterruptible (blocked) state
>-			*Be aware* that this option may print a _lot_ of lines,
>-			so there are risks of losing older messages in the log.
>-			Use this option carefully, maybe worth to setup a
>-			bigger log buffer with "log_buf_len" along with this.
>+
>+			*Be aware* that this option may print a _lot_ of lines.
>+
>+			There is an increased risk of losing older messages in
>+			the log. Maybe worth to setup a	bigger log buffer with
>+			"log_buf_len" along with this.
>+
>+			Also consider using "printk.console_no_auto_verbose=Y"
>+			if using this along with pstore, to avoid extra delays
>+			due to increased console verbosity during panic.
> 
> 	panic_sys_info= A comma separated list of extra information to be dumped
>                         on panic.
>@@ -4900,7 +4907,9 @@ Kernel parameters
>                         all_bt:         print all CPUs backtrace (if available in the arch)
>                         blocked_tasks:  print only tasks in uninterruptible (blocked) state
> 
>-                        This is a human readable alternative to the 'panic_print' option.
>+			This is a human readable alternative to the 'panic_print'
>+			option above. Please be aware of the caveats using this,
>+			check the 'panic_print' parameter for more details.
> 
> 	panic_console_replay
> 			When panic happens, replay all kernel messages on
>

Thanks!