From: John Ogness Date: Tue, 20 Aug 2024 08:35:45 +0206 Subject: [PATCH 19/54] printk: nbcon: Add helper to assign priority based on CPU state Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.11/older/patches-6.11-rt7.tar.xz Add a helper function to use the current state of the CPU to determine which priority to assign to the printing context. The EMERGENCY priority handling is added in a follow-up commit. It will use a per-CPU variable. Note: nbcon_device_try_acquire(), which is used by console drivers to acquire the nbcon console for non-printing activities, is hard-coded to always use NORMAL priority. Signed-off-by: John Ogness Reviewed-by: Petr Mladek Link: https://lore.kernel.org/r/20240820063001.36405-20-john.ogness@linutronix.de Signed-off-by: Petr Mladek Signed-off-by: Sebastian Andrzej Siewior --- kernel/printk/internal.h | 2 ++ kernel/printk/nbcon.c | 19 +++++++++++++++++++ 2 files changed, 21 insertions(+) --- a/kernel/printk/internal.h +++ b/kernel/printk/internal.h @@ -83,6 +83,7 @@ u64 nbcon_seq_read(struct console *con); void nbcon_seq_force(struct console *con, u64 seq); bool nbcon_alloc(struct console *con); void nbcon_free(struct console *con); +enum nbcon_prio nbcon_get_default_prio(void); /* * Check if the given console is currently capable and allowed to print @@ -136,6 +137,7 @@ static inline u64 nbcon_seq_read(struct static inline void nbcon_seq_force(struct console *con, u64 seq) { } static inline bool nbcon_alloc(struct console *con) { return false; } static inline void nbcon_free(struct console *con) { } +static inline enum nbcon_prio nbcon_get_default_prio(void) { return NBCON_PRIO_NONE; } static inline bool console_is_usable(struct console *con, short flags) { return false; } --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -974,6 +974,25 @@ static bool nbcon_emit_next_record(struc } /** + * nbcon_get_default_prio - The appropriate nbcon priority to use for nbcon + * printing on the current CPU + * + * Context: Any context. + * Return: The nbcon_prio to use for acquiring an nbcon console in this + * context for printing. + * + * The function is safe for reading per-CPU data in any context because + * preemption is disabled if the current CPU is in the panic state. + */ +enum nbcon_prio nbcon_get_default_prio(void) +{ + if (this_cpu_in_panic()) + return NBCON_PRIO_PANIC; + + return NBCON_PRIO_NORMAL; +} + +/** * nbcon_alloc - Allocate and init the nbcon console specific data * @con: Console to initialize *