linux-toradex.git/kernel/printk, branch v6.2-rc3

Merge branch 'rework/console-list-lock' into for-linus

2022-12-08T10:46:56+00:00

printk: htmldocs: add missing description

2022-12-02T10:25:02+00:00

Variable and return descriptions were missing from the SRCU read
lock functions. Add them.

Signed-off-by: John Ogness 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/87zgcjpdvo.fsf@jogness.linutronix.de

printk: relieve console_lock of list synchronization duties

2022-12-02T10:25:02+00:00

The console_list_lock provides synchronization for console list and
console->flags updates. All call sites that were using the console_lock
for this synchronization have either switched to use the
console_list_lock or the SRCU list iterator.

Remove console_lock usage for console list updates and console->flags
updates.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20221116162152.193147-40-john.ogness@linutronix.de

printk, xen: fbfront: create/use safe function for forcing preferred

2022-12-02T10:25:02+00:00

With commit 9e124fe16ff2("xen: Enable console tty by default in domU
if it's not a dummy") a hack was implemented to make sure that the
tty console remains the console behind the /dev/console device. The
main problem with the hack is that, after getting the console pointer
to the tty console, it is assumed the pointer is still valid after
releasing the console_sem. This assumption is incorrect and unsafe.

Make the hack safe by introducing a new function
console_force_preferred_locked() and perform the full operation
under the console_list_lock.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20221116162152.193147-33-john.ogness@linutronix.de

console: introduce console_is_registered()

2022-12-02T10:25:01+00:00

Currently it is not possible for drivers to detect if they have
already successfully registered their console. Several drivers
have multiple paths that lead to console registration. To avoid
attempting a 2nd registration (which leads to a WARN), drivers
are implementing their own solution.

Introduce console_is_registered() so drivers can easily identify
if their console is currently registered. A _locked() variant
is also provided if the caller is already holding the
console_list_lock.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20221116162152.193147-22-john.ogness@linutronix.de

printk: console_device: use srcu console list iterator

2022-12-02T10:25:01+00:00

Use srcu console list iteration for console list traversal. It is
acceptable because the consoles might come and go at any time.
Strict synchronizing with console registration code would not bring
any advantage over srcu.

Document why the console_lock is still necessary. Note that this
is a preparatory change for when console_lock no longer provides
synchronization for the console list.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20221116162152.193147-21-john.ogness@linutronix.de

printk: console_flush_on_panic: use srcu console list iterator

2022-12-02T10:25:01+00:00

With SRCU it is now safe to traverse the console list, even if
the console_trylock() failed. However, overwriting console->seq
when console_trylock() failed is still an issue.

Switch to SRCU iteration and document remaining issue with
console->seq.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20221116162152.193147-20-john.ogness@linutronix.de

printk: console_unblank: use srcu console list iterator

2022-12-02T10:25:00+00:00

Use srcu console list iteration for console list traversal.

Document why the console_lock is still necessary. Note that this
is a preparatory change for when console_lock no longer provides
synchronization for the console list.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20221116162152.193147-19-john.ogness@linutronix.de

printk: console_is_usable: use console_srcu_read_flags

2022-12-02T10:25:00+00:00

All users of console_is_usable() are SRCU iterators. Use the
appropriate wrapper function to locklessly read the flags.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20221116162152.193147-18-john.ogness@linutronix.de

printk: __pr_flush: use srcu console list iterator

2022-12-02T10:25:00+00:00

Use srcu console list iteration for console list traversal.

Document why the console_lock is still necessary. Note that this
is a preparatory change for when console_lock no longer provides
synchronization for the console list.

Signed-off-by: John Ogness 
Reviewed-by: Petr Mladek 
Signed-off-by: Petr Mladek 
Link: https://lore.kernel.org/r/20221116162152.193147-17-john.ogness@linutronix.de