From 3c8206a9c295124cfff105092a0c86df62c5bd12 Mon Sep 17 00:00:00 2001 From: John Ogness <john.ogness@linutronix.de> Date: Tue, 19 Sep 2023 14:33:27 +0000 Subject: [PATCH 133/204] printk: nbcon: Use nbcon consoles in console_flush_all() Allow nbcon consoles to print messages in the printk() caller context by integrating them into console_flush_all(). The write_atomic() callback is used for printing. Provide nbcon_console_emit_next_record(), which acts as the nbcon variant of console_emit_next_record(). Call this variant within console_flush_all() for nbcon consoles. Since nbcon consoles use their own @nbcon_seq variable to track the next record to print, this also must be appropriately handled. Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- kernel/printk/internal.h | 5 ++++ kernel/printk/nbcon.c | 50 +++++++++++++++++++++++++++++++++++++++++++++++ kernel/printk/printk.c | 19 +++++++++++++---- 3 files changed, 69 insertions(+), 5 deletions(-) Index: linux-6.6.58-rt45/kernel/printk/internal.h =================================================================== @ linux-6.6.58-rt45/kernel/printk/internal.h:74 @ void defer_console_output(void); u16 printk_parse_prefix(const char *text, int *level, enum printk_info_flags *flags); +void console_lock_spinning_enable(void); +int console_lock_spinning_disable_and_check(int cookie); u64 nbcon_seq_read(struct console *con); void nbcon_seq_force(struct console *con, u64 seq); @ linux-6.6.58-rt45/kernel/printk/internal.h:83 @ bool nbcon_alloc(struct console *con); void nbcon_init(struct console *con); void nbcon_free(struct console *con); void nbcon_atomic_flush_all(void); +bool nbcon_atomic_emit_next_record(struct console *con, bool *handover, int cookie); /* * Check if the given console is currently capable and allowed to print @ linux-6.6.58-rt45/kernel/printk/internal.h:139 @ static inline bool nbcon_alloc(struct co static inline void nbcon_init(struct console *con) { } static inline void nbcon_free(struct console *con) { } static inline void nbcon_atomic_flush_all(void) { } +static inline bool nbcon_atomic_emit_next_record(struct console *con, bool *handover, + int cookie) { return false; } static inline bool console_is_usable(struct console *con, short flags) { return false; } Index: linux-6.6.58-rt45/kernel/printk/nbcon.c =================================================================== --- linux-6.6.58-rt45.orig/kernel/printk/nbcon.c +++ linux-6.6.58-rt45/kernel/printk/nbcon.c @ linux-6.6.58-rt45/kernel/printk/internal.h:535 @ static struct printk_buffers panic_nbcon * nbcon_context_try_acquire - Try to acquire nbcon console * @ctxt: The context of the caller * + * Context: Any context which could not be migrated to another CPU. * Return: True if the console was acquired. False otherwise. * * If the caller allowed an unsafe hostile takeover, on success the @ linux-6.6.58-rt45/kernel/printk/internal.h:965 @ static bool nbcon_atomic_emit_one(struct } /** + * nbcon_atomic_emit_next_record - Print one record for an nbcon console + * using the write_atomic() callback + * @con: The console to print on + * @handover: Will be set to true if a printk waiter has taken over the + * console_lock, in which case the caller is no longer holding + * both the console_lock and the SRCU read lock. Otherwise it + * is set to false. + * @cookie: The cookie from the SRCU read lock. + * + * Context: Any context which could not be migrated to another CPU. + * Return: True if a record could be printed, otherwise false. + * + * This function is meant to be called by console_flush_all() to print records + * on nbcon consoles using the write_atomic() callback. Essentially it is the + * nbcon version of console_emit_next_record(). + */ +bool nbcon_atomic_emit_next_record(struct console *con, bool *handover, int cookie) +{ + struct nbcon_write_context wctxt = { }; + struct nbcon_context *ctxt = &ACCESS_PRIVATE(&wctxt, ctxt); + unsigned long driver_flags; + bool progress = false; + unsigned long flags; + + *handover = false; + + /* Use the same locking order as console_emit_next_record(). */ + printk_safe_enter_irqsave(flags); + console_lock_spinning_enable(); + stop_critical_timings(); + + con->driver_enter(con, &driver_flags); + cant_migrate(); + + ctxt->console = con; + ctxt->prio = NBCON_PRIO_NORMAL; + + progress = nbcon_atomic_emit_one(&wctxt); + + con->driver_exit(con, driver_flags); + + start_critical_timings(); + *handover = console_lock_spinning_disable_and_check(cookie); + printk_safe_exit_irqrestore(flags); + + return progress; +} + +/** * __nbcon_atomic_flush_all - Flush all nbcon consoles using their * write_atomic() callback * @stop_seq: Flush up until this record Index: linux-6.6.58-rt45/kernel/printk/printk.c =================================================================== --- linux-6.6.58-rt45.orig/kernel/printk/printk.c +++ linux-6.6.58-rt45/kernel/printk/printk.c @ linux-6.6.58-rt45/kernel/printk/internal.h:1875 @ static bool console_waiter; * there may be a waiter spinning (like a spinlock). Also it must be * ready to hand over the lock at the end of the section. */ -static void console_lock_spinning_enable(void) +void console_lock_spinning_enable(void) { /* * Do not use spinning in panic(). The panic CPU wants to keep the lock. @ linux-6.6.58-rt45/kernel/printk/internal.h:1914 @ lockdep: * * Return: 1 if the lock rights were passed, 0 otherwise. */ -static int console_lock_spinning_disable_and_check(int cookie) +int console_lock_spinning_disable_and_check(int cookie) { int waiter; @ linux-6.6.58-rt45/kernel/printk/internal.h:2958 @ static bool console_flush_all(bool do_co cookie = console_srcu_read_lock(); for_each_console_srcu(con) { short flags = console_srcu_read_flags(con); + u64 printk_seq; bool progress; if (!console_is_usable(con, flags)) continue; any_usable = true; - progress = console_emit_next_record(con, handover, cookie); + if (flags & CON_NBCON) { + progress = nbcon_atomic_emit_next_record(con, handover, cookie); + + printk_seq = nbcon_seq_read(con); + } else { + progress = console_emit_next_record(con, handover, cookie); + + printk_seq = con->seq; + } /* * If a handover has occurred, the SRCU read lock @ linux-6.6.58-rt45/kernel/printk/internal.h:2983 @ static bool console_flush_all(bool do_co return false; /* Track the next of the highest seq flushed. */ - if (con->seq > *next_seq) - *next_seq = con->seq; + if (printk_seq > *next_seq) + *next_seq = printk_seq; if (!progress) continue;