linux-stable.git/include/linux/printk.h, branch v6.12.91

lib/hexdump: print_hex_dump_bytes() calls print_hex_dump_debug()

2026-05-23T11:04:46+00:00

[ Upstream commit 36776b7f8a8955b4e75b5d490a75fee0c7a2a7ef ]

print_hex_dump_bytes() claims to be a simple wrapper around
print_hex_dump(), but it actally calls print_hex_dump_debug(), which
means no output is printed if (dynamic) DEBUG is disabled.

Update the documentation to match the implementation.

Fixes: 091cb0994edd20d6 ("lib/hexdump: make print_hex_dump_bytes() a nop on !DEBUG builds")
Signed-off-by: Geert Uytterhoeven 
Reviewed-by: Petr Mladek 
Link: https://patch.msgid.link/3d5c3069fd9102ecaf81d044b750cd613eb72a08.1774970392.git.geert+renesas@glider.be
Signed-off-by: Petr Mladek 
Signed-off-by: Sasha Levin

printk: add print_hex_dump_devel()

2026-05-14T13:29:29+00:00

[ Upstream commit d134feeb5df33fbf77f482f52a366a44642dba09 ]

Add print_hex_dump_devel() as the hex dump equivalent of pr_devel(),
which emits output only when DEBUG is enabled, but keeps call sites
compiled otherwise.

Suggested-by: Herbert Xu 
Signed-off-by: Thorsten Blum 
Reviewed-by: John Ogness 
Signed-off-by: Herbert Xu 
Stable-dep-of: 177730a273b1 ("crypto: caam - guard HMAC key hex dumps in hash_digest_key")
Signed-off-by: Sasha Levin 
Signed-off-by: Greg Kroah-Hartman

Flush console log from kernel_power_off()

2025-04-20T08:15:12+00:00

[ Upstream commit 6ea9a1781c70a8be1fcdc49134fc1bf4baba8bca ]

Kernels built with CONFIG_PREEMPT_RT=y can lose significant console output
and shutdown time, which hides shutdown-time RCU issues from rcutorture.
Therefore, make pr_flush() public and invoke it after then last print
in kernel_power_off().

[ paulmck: Apply John Ogness feedback. ]
[ paulmck: Appy Sebastian Andrzej Siewior feedback. ]
[ paulmck: Apply kernel test robot feedback. ]

Signed-off-by: Paul E. McKenney 
Reviewed-by: John Ogness 
Reviewed-by: Petr Mladek 
Cc: Steven Rostedt 
Cc: Sergey Senozhatsky 
Link: https://lore.kernel.org/r/5f743488-dc2a-4f19-bdda-cf50b9314832@paulmck-laptop
Signed-off-by: Boqun Feng 
Signed-off-by: Sasha Levin

printk: Coordinate direct printing in panic

2024-08-21T12:56:25+00:00

If legacy and nbcon consoles are registered and the nbcon
consoles are allowed to flush (i.e. no boot consoles
registered), the legacy consoles will no longer perform
direct printing on the panic CPU until after the backtrace
has been stored. This will give the safe nbcon consoles a
chance to print the panic messages before allowing the
unsafe legacy consoles to print.

If no nbcon consoles are registered or they are not allowed
to flush because boot consoles are registered, there is no
change in behavior (i.e. legacy consoles will always attempt
to print from the printk() caller context).

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Link: https://lore.kernel.org/r/20240820063001.36405-30-john.ogness@linutronix.de
Signed-off-by: Petr Mladek

printk: nbcon: Add unsafe flushing on panic

2024-08-21T12:56:24+00:00

Add nbcon_atomic_flush_unsafe() to flush all nbcon consoles
using the write_atomic() callback and allowing unsafe hostile
takeovers. Call this at the end of panic() as a final attempt
to flush any pending messages.

Note that legacy consoles use unsafe methods for flushing
from the beginning of panic (see bust_spinlocks()). Therefore,
systems using both legacy and nbcon consoles may still fail to
see panic messages due to unsafe legacy console usage.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Link: https://lore.kernel.org/r/20240820063001.36405-27-john.ogness@linutronix.de
Signed-off-by: Petr Mladek

nbcon: Add API to acquire context for non-printing operations

2024-08-21T12:56:23+00:00

Provide functions nbcon_device_try_acquire() and
nbcon_device_release() which will try to acquire the nbcon
console ownership with NBCON_PRIO_NORMAL and mark it unsafe for
handover/takeover.

These functions are to be used together with the device-specific
locking when performing non-printing activities on the console
device. They will allow synchronization against the
atomic_write() callback which will be serialized, for higher
priority contexts, only by acquiring the console context
ownership.

Pitfalls:

The API requires to be called in a context with migration
disabled because it uses per-CPU variables internally.

The context is set unsafe for a takeover all the time. It
guarantees full serialization against any atomic_write() caller
except for the final flush in panic() which might try an unsafe
takeover.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Link: https://lore.kernel.org/r/20240820063001.36405-14-john.ogness@linutronix.de
Signed-off-by: Petr Mladek

printk: Check printk_deferred_enter()/_exit() usage

2024-08-21T12:56:22+00:00

Add validation that printk_deferred_enter()/_exit() are called in
non-migration contexts.

Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Link: https://lore.kernel.org/r/20240820063001.36405-5-john.ogness@linutronix.de
Signed-off-by: Petr Mladek

Merge tag 'printk-for-6.11-trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2024-07-25T20:18:41+00:00

Pull printk updates from Petr Mladek:

 - trivial printk changes

The bigger "real" printk work is still being discussed.

* tag 'printk-for-6.11-trivial' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  vsprintf: add missing MODULE_DESCRIPTION() macro
  printk: Rename console_replay_all() and update context

printk: Add match_devname_and_update_preferred_console()

2024-07-04T13:41:44+00:00

Let's add match_devname_and_update_preferred_console() for driver
subsystems to call during init when the console is ready, and it's
character device name is known. For now, we use it only for the serial
layer to allow console=DEVNAME:0.0 style hardware based addressing for
consoles.

The earlier attempt on doing this caused a regression with the kernel
command line console order as it added calling __add_preferred_console()
again later on during init. A better approach was suggested by Petr where
we add the deferred console to the console_cmdline[] and update it later
on when the console is ready.

Suggested-by: Petr Mladek 
Co-developed-by: Petr Mladek 
Signed-off-by: Tony Lindgren 
Reviewed-by: Petr Mladek 
Link: https://lore.kernel.org/r/20240703100615.118762-2-tony.lindgren@linux.intel.com
Signed-off-by: Greg Kroah-Hartman

Revert "printk: Save console options for add_preferred_console_match()"

2024-06-25T05:58:10+00:00

This reverts commit f03e8c1060f86c23eb49bafee99d9fcbd1c1bd77.

Let's roll back all of the serial core and printk console changes that
went into 6.10-rc1 as there still are problems with them that need to be
sorted out.

Link: https://lore.kernel.org/r/ZnpRozsdw6zbjqze@tlindgre-MOBL1
Reported-by: Petr Mladek 
Reported-by: Tony Lindgren 
Cc: Jiri Slaby 
Cc: John Ogness 
Cc: Sergey Senozhatsky 
Cc: Andy Shevchenko 
Cc: Ilpo Järvinen 
Signed-off-by: Greg Kroah-Hartman