kernel/linux.git/include/linux/console.h, branch v6.19.11

Merge tag 'printk-for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux

2025-12-03T20:42:36+00:00

Pull printk updates from Petr Mladek: - Allow creaing nbcon console drivers with an unsafe write_atomic() callback that can only be called by the final nbcon_atomic_flush_unsafe(). Otherwise, the driver would rely on the kthread. It is going to be used as the-best-effort approach for an experimental nbcon netconsole driver, see https://lore.kernel.org/r/20251121-nbcon-v1-2-503d17b2b4af@debian.org Note that a safe .write_atomic() callback is supposed to work in NMI context. But some networking drivers are not safe even in IRQ context: https://lore.kernel.org/r/oc46gdpmmlly5o44obvmoatfqo5bhpgv7pabpvb6sjuqioymcg@gjsma3ghoz35 In an ideal world, all networking drivers would be fixed first and the atomic flush would be blocked only in NMI context. But it brings the question how reliable networking drivers are when the system is in a bad state. They might block flushing more reliable serial consoles which are more suitable for serious debugging anyway. - Allow to use the last 4 bytes of the printk ring buffer. - Prevent queuing IRQ work and block printk kthreads when consoles are suspended. Otherwise, they create non-necessary churn or even block the suspend. - Release console_lock() between each record in the kthread used for legacy consoles on RT. It might significantly speed up the boot. - Release nbcon context between each record in the atomic flush. It prevents stalls of the related printk kthread after it has lost the ownership in the middle of a record - Add support for NBCON consoles into KDB - Add %ptsP modifier for printing struct timespec64 and use it where possible - Misc code clean up * tag 'printk-for-6.19' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: (48 commits) printk: Use console_is_usable on console_unblank arch: um: kmsg_dump: Use console_is_usable drivers: serial: kgdboc: Drop checks for CON_ENABLED and CON_BOOT lib/vsprintf: Unify FORMAT_STATE_NUM handlers printk: Avoid irq_work for printk_deferred() on suspend printk: Avoid scheduling irq_work on suspend printk: Allow printk_trigger_flush() to flush all types tracing: Switch to use %ptSp scsi: snic: Switch to use %ptSp scsi: fnic: Switch to use %ptSp s390/dasd: Switch to use %ptSp ptp: ocp: Switch to use %ptSp pps: Switch to use %ptSp PCI: epf-test: Switch to use %ptSp net: dsa: sja1105: Switch to use %ptSp mmc: mmc_test: Switch to use %ptSp media: av7110: Switch to use %ptSp ipmi: Switch to use %ptSp igb: Switch to use %ptSp e1000e: Switch to use %ptSp ...

printk: nbcon: Allow unsafe write_atomic() for panic

2025-11-07T13:30:52+00:00

There may be console drivers that have not yet figured out a way to implement safe atomic printing (->write_atomic() callback). These drivers could choose to only implement threaded printing (->write_thread() callback), but then it is guaranteed that _no_ output will be printed during panic. Not even attempted. As a result, developers may be tempted to implement unsafe ->write_atomic() callbacks and/or implement some sort of custom deferred printing trickery to try to make it work. This goes against the principle intention of the nbcon API as well as endangers other nbcon drivers that are doing things correctly (safely). As a compromise, allow nbcon drivers to implement unsafe ->write_atomic() callbacks by providing a new console flag CON_NBCON_ATOMIC_UNSAFE. When specified, the ->write_atomic() callback for that console will _only_ be called during the final "hope and pray" flush attempt at the end of a panic: nbcon_atomic_flush_unsafe(). Signed-off-by: John Ogness Link: https://lore.kernel.org/lkml/b2qps3uywhmjaym4mht2wpxul4yqtuuayeoq4iv4k3zf5wdgh3@tocu6c7mj4lt Reviewed-by: Petr Mladek Link: https://lore.kernel.org/all/swdpckuwwlv3uiessmtnf2jwlx3jusw6u7fpk5iggqo4t2vdws@7rpjso4gr7qp/ [1] Link: https://lore.kernel.org/all/20251103-fix_netpoll_aa-v4-1-4cfecdf6da7c@debian.org/ [2] Link: https://patch.msgid.link/20251027161212.334219-2-john.ogness@linutronix.de [pmladek@suse.com: Fix build with rework/nbcon-in-kdb branch.] Signed-off-by: Petr Mladek

kdb: Adapt kdb_msg_write to work with NBCON consoles

2025-10-24T10:56:20+00:00

Function kdb_msg_write was calling con->write for any found console, but it won't work on NBCON consoles. In this case we should acquire the ownership of the console using NBCON_PRIO_EMERGENCY, since printing kdb messages should only be interrupted by a panic. At this point, the console is required to use the atomic callback. The console is skipped if the write_atomic callback is not set or if the context could not be acquired. The validation of NBCON is done by the console_is_usable helper. The context is released right after write_atomic finishes. The oops_in_progress handling is only needed in the legacy consoles, so it was moved around the con->write callback. Suggested-by: Petr Mladek Reviewed-by: Petr Mladek Reviewed-by: John Ogness Signed-off-by: Marcos Paulo de Souza Link: https://patch.msgid.link/20251016-nbcon-kgdboc-v6-5-866aac60a80e@suse.com [pmladek@suse.com: Fixed compilation with !CONFIG_PRINTK.] Signed-off-by: Petr Mladek

printk: nbcon: Export nbcon_write_context_set_buf

2025-10-24T10:56:19+00:00

This function will be used in the next patch to allow a driver to set both the message and message length of a nbcon_write_context. This is necessary because the function also initializes the ->unsafe_takeover struct member. By using this helper we ensure that the struct is initialized correctly. Reviewed-by: Petr Mladek Reviewed-by: John Ogness Signed-off-by: Marcos Paulo de Souza Link: https://patch.msgid.link/20251016-nbcon-kgdboc-v6-4-866aac60a80e@suse.com Signed-off-by: Petr Mladek

printk: nbcon: Introduce KDB helpers

2025-10-24T10:19:23+00:00

These helpers will be used when calling console->write_atomic on KDB code in the next patch. It's basically the same implementation as nbcon_device_try_acquire, but using NBCON_PRIO_EMERGENCY when acquiring the context. If the acquire succeeds, the message and message length are assigned to nbcon_write_context so ->write_atomic can print the message. After release try to flush the console since there may be a backlog of messages in the ringbuffer. The kthread console printers do not get a chance to run while kdb is active. Reviewed-by: Petr Mladek Reviewed-by: John Ogness Signed-off-by: Marcos Paulo de Souza Link: https://patch.msgid.link/20251016-nbcon-kgdboc-v6-2-866aac60a80e@suse.com Signed-off-by: Petr Mladek

printk: nbcon: Export console_is_usable

2025-10-24T10:19:23+00:00

The helper will be used on KDB code in the next commits. Reviewed-by: Petr Mladek Reviewed-by: John Ogness Signed-off-by: Marcos Paulo de Souza Link: https://patch.msgid.link/20251016-nbcon-kgdboc-v6-1-866aac60a80e@suse.com Signed-off-by: Petr Mladek

console: introduce console_lock guard()s

2025-08-17T10:46:25+00:00

Having this, guards like these work: guard(console_lock)(); or scoped_guard(console_lock) { ... } See e.g. "vc_screen: use guard()s" later in this series. Signed-off-by: "Jiri Slaby (SUSE)" Link: https://lore.kernel.org/r/20250814072456.182853-2-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

printk: Rename console_start to console_resume

2025-03-11T11:51:21+00:00

The intent of console_start was to resume a previously suspended console, so rename it accordingly. Signed-off-by: Marcos Paulo de Souza Reviewed-by: Petr Mladek Reviewed-by: John Ogness Link: https://lore.kernel.org/r/20250226-printk-renaming-v1-4-0b878577f2e6@suse.com [pmladek@suse.com: Fixed typo in the commit message. Updated also new drm_log.c.] Signed-off-by: Petr Mladek

printk: Rename console_stop to console_suspend

2025-03-11T11:41:55+00:00

The intent of console_stop was in fact to suspend it, so rename the function accordingly. Signed-off-by: Marcos Paulo de Souza Reviewed-by: Petr Mladek Reviewed-by: John Ogness Link: https://lore.kernel.org/r/20250226-printk-renaming-v1-3-0b878577f2e6@suse.com [pmladek@suse.com: Fixed typo in the commit message. Updated also new drm_log.c] Signed-off-by: Petr Mladek

printk: Rename resume_console to console_resume_all

2025-03-11T10:51:27+00:00

The function resume_console has a misleading name, since it resumes all consoles, so rename it accordingly. Signed-off-by: Marcos Paulo de Souza Reviewed-by: Petr Mladek Reviewed-by: John Ogness Link: https://lore.kernel.org/r/20250226-printk-renaming-v1-2-0b878577f2e6@suse.com [pmladek@suse.com: Fixed typo in the commit message.] Signed-off-by: Petr Mladek