From 2af5f21476f3b732adfcfac9cd4077601ec01f9e Mon Sep 17 00:00:00 2001 From: John Ogness Date: Wed, 13 Sep 2023 08:35:23 +0000 Subject: [PATCH 124/184] printk: nbcon: Implement processing in port->lock wrapper Currently the port->lock wrappers nbcon_handle_port_lock(), nbcon_handle_port_unlock() (and their variants) only lock/unlock the spin_lock. If the port is an nbcon console, the wrappers must also acquire/release the console and mark the region as unsafe. This allows general port->lock synchronization to be synchronized with the nbcon console ownership. Signed-off-by: John Ogness Signed-off-by: Sebastian Andrzej Siewior --- include/linux/console.h | 2 + include/linux/printk.h | 13 ++++++ include/linux/serial_core.h | 18 ++++++++- kernel/printk/nbcon.c | 79 +++++++++++++++++++++++++++++++++++++ 4 files changed, 110 insertions(+), 2 deletions(-) diff --git a/include/linux/console.h b/include/linux/console.h index e4fc6f7c1496..c27bd5189660 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -299,6 +299,7 @@ struct nbcon_write_context { * @nbcon_state: State for nbcon consoles * @nbcon_seq: Sequence number of the next record for nbcon to print * @pbufs: Pointer to nbcon private buffer + * @locked_port: True, if the port lock is locked by nbcon */ struct console { char name[16]; @@ -325,6 +326,7 @@ struct console { atomic_t __private nbcon_state; atomic_long_t __private nbcon_seq; struct printk_buffers *pbufs; + bool locked_port; }; #ifdef CONFIG_LOCKDEP diff --git a/include/linux/printk.h b/include/linux/printk.h index 8ef499ab3c1e..9b2dca459423 100644 --- a/include/linux/printk.h +++ b/include/linux/printk.h @@ -9,6 +9,8 @@ #include #include +struct uart_port; + extern const char linux_banner[]; extern const char linux_proc_banner[]; @@ -192,6 +194,8 @@ void show_regs_print_info(const char *log_lvl); extern asmlinkage void dump_stack_lvl(const char *log_lvl) __cold; extern asmlinkage void dump_stack(void) __cold; void printk_trigger_flush(void); +extern void nbcon_handle_port_lock(struct uart_port *up); +extern void nbcon_handle_port_unlock(struct uart_port *up); #else static inline __printf(1, 0) int vprintk(const char *s, va_list args) @@ -271,6 +275,15 @@ static inline void dump_stack(void) static inline void printk_trigger_flush(void) { } + +static inline void nbcon_handle_port_lock(struct uart_port *up) +{ +} + +static inline void nbcon_handle_port_unlock(struct uart_port *up) +{ +} + #endif #ifdef CONFIG_SMP diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 3091c62ec37b..18ce60b40f1e 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -595,6 +595,7 @@ struct uart_port { static inline void uart_port_lock(struct uart_port *up) { spin_lock(&up->lock); + nbcon_handle_port_lock(up); } /** @@ -604,6 +605,7 @@ static inline void uart_port_lock(struct uart_port *up) static inline void uart_port_lock_irq(struct uart_port *up) { spin_lock_irq(&up->lock); + nbcon_handle_port_lock(up); } /** @@ -614,6 +616,7 @@ static inline void uart_port_lock_irq(struct uart_port *up) static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *flags) { spin_lock_irqsave(&up->lock, *flags); + nbcon_handle_port_lock(up); } /** @@ -624,7 +627,11 @@ static inline void uart_port_lock_irqsave(struct uart_port *up, unsigned long *f */ static inline bool uart_port_trylock(struct uart_port *up) { - return spin_trylock(&up->lock); + if (!spin_trylock(&up->lock)) + return false; + + nbcon_handle_port_lock(up); + return true; } /** @@ -636,7 +643,11 @@ static inline bool uart_port_trylock(struct uart_port *up) */ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long *flags) { - return spin_trylock_irqsave(&up->lock, *flags); + if (!spin_trylock_irqsave(&up->lock, *flags)) + return false; + + nbcon_handle_port_lock(up); + return true; } /** @@ -645,6 +656,7 @@ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long */ static inline void uart_port_unlock(struct uart_port *up) { + nbcon_handle_port_unlock(up); spin_unlock(&up->lock); } @@ -654,6 +666,7 @@ static inline void uart_port_unlock(struct uart_port *up) */ static inline void uart_port_unlock_irq(struct uart_port *up) { + nbcon_handle_port_unlock(up); spin_unlock_irq(&up->lock); } @@ -664,6 +677,7 @@ static inline void uart_port_unlock_irq(struct uart_port *up) */ static inline void uart_port_unlock_irqrestore(struct uart_port *up, unsigned long flags) { + nbcon_handle_port_unlock(up); spin_unlock_irqrestore(&up->lock, flags); } diff --git a/kernel/printk/nbcon.c b/kernel/printk/nbcon.c index 560d3c478ac1..8eb7d5f17e7e 100644 --- a/kernel/printk/nbcon.c +++ b/kernel/printk/nbcon.c @@ -6,6 +6,7 @@ #include #include #include +#include #include "internal.h" /* * Printk console printing implementation for consoles which does not depend @@ -1031,3 +1032,81 @@ void nbcon_free(struct console *con) con->pbufs = NULL; } + +static inline bool uart_is_nbcon(struct uart_port *up) +{ + int cookie; + bool ret; + + if (!uart_console(up)) + return false; + + cookie = console_srcu_read_lock(); + ret = (console_srcu_read_flags(up->cons) & CON_NBCON); + console_srcu_read_unlock(cookie); + return ret; +} + +/** + * nbcon_handle_port_lock - The second half of the port locking wrapper + * @up: The uart port whose @lock was locked + * + * The uart_port_lock() wrappers will first lock the spin_lock @up->lock. + * Then this function is called to implement nbcon-specific processing. + * + * If @up is an nbcon console, this console will be acquired and marked as + * unsafe. Otherwise this function does nothing. + */ +void nbcon_handle_port_lock(struct uart_port *up) +{ + struct console *con = up->cons; + struct nbcon_context ctxt; + + if (!uart_is_nbcon(up)) + return; + + WARN_ON_ONCE(con->locked_port); + + do { + do { + memset(&ctxt, 0, sizeof(ctxt)); + ctxt.console = con; + ctxt.prio = NBCON_PRIO_NORMAL; + } while (!nbcon_context_try_acquire(&ctxt)); + + } while (!nbcon_context_enter_unsafe(&ctxt)); + + con->locked_port = true; +} +EXPORT_SYMBOL_GPL(nbcon_handle_port_lock); + +/** + * nbcon_handle_port_unlock - The first half of the port unlocking wrapper + * @up: The uart port whose @lock is about to be unlocked + * + * The uart_port_unlock() wrappers will first call this function to implement + * nbcon-specific processing. Then afterwards the uart_port_unlock() wrappers + * will unlock the spin_lock @up->lock. + * + * If @up is an nbcon console, the console will be marked as safe and + * released. Otherwise this function does nothing. + */ +void nbcon_handle_port_unlock(struct uart_port *up) +{ + struct console *con = up->cons; + struct nbcon_context ctxt = { + .console = con, + .prio = NBCON_PRIO_NORMAL, + }; + + if (!uart_is_nbcon(up)) + return; + + WARN_ON_ONCE(!con->locked_port); + + if (nbcon_context_exit_unsafe(&ctxt)) + nbcon_context_release(&ctxt); + + con->locked_port = false; +} +EXPORT_SYMBOL_GPL(nbcon_handle_port_unlock); -- 2.34.1