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serial: core: Acquire nbcon context in port->lock wrapper

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Currently the port->lock wrappers uart_port_lock(),
uart_port_unlock() (and their variants) only lock/unlock
the spin_lock.

If the port is an nbcon console that has implemented the
write_atomic() callback, the wrappers must also acquire/release
the console context and mark the region as unsafe. This allows
general port->lock synchronization to be synchronized against
the nbcon write_atomic() callback.

Note that __uart_port_using_nbcon() relies on the port->lock
being held while a console is added and removed from the
console list (i.e. all uart nbcon drivers *must* take the
port->lock in their device_lock() callbacks).

Signed-off-by: John Ogness <john.ogness@linutronix.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20240820063001.36405-15-john.ogness@linutronix.de
Signed-off-by: Petr Mladek <pmladek@suse.com>
This commit is contained in:
John Ogness 2024-08-20 08:35:40 +02:06 committed by Petr Mladek
parent adf6f37d14
commit 4126f149c4
1 changed files with 80 additions and 2 deletions
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82
include/linux/serial_core.h
View File

@ -11,6 +11,8 @@
#include <linux/compiler.h>
#include <linux/console.h>
#include <linux/interrupt.h>
#include <linux/lockdep.h>
#include <linux/printk.h>
#include <linux/spinlock.h>
#include <linux/sched.h>
#include <linux/tty.h>
@ -625,6 +627,60 @@ static inline void uart_port_set_cons(struct uart_port *up, struct console *con)
up->cons = con;
__uart_port_unlock_irqrestore(up, flags);
}
/* Only for internal port lock wrapper usage. */
static inline bool __uart_port_using_nbcon(struct uart_port *up)
{
lockdep_assert_held_once(&up->lock);
if (likely(!uart_console(up)))
return false;
/*
* @up->cons is only modified under the port lock. Therefore it is
* certain that it cannot disappear here.
*
* @up->cons->node is added/removed from the console list under the
* port lock. Therefore it is certain that the registration status
* cannot change here, thus @up->cons->flags can be read directly.
*/
if (hlist_unhashed_lockless(&up->cons->node) ||
!(up->cons->flags & CON_NBCON) ||
!up->cons->write_atomic) {
return false;
}
return true;
}
/* Only for internal port lock wrapper usage. */
static inline bool __uart_port_nbcon_try_acquire(struct uart_port *up)
{
if (!__uart_port_using_nbcon(up))
return true;
return nbcon_device_try_acquire(up->cons);
}
/* Only for internal port lock wrapper usage. */
static inline void __uart_port_nbcon_acquire(struct uart_port *up)
{
if (!__uart_port_using_nbcon(up))
return;
while (!nbcon_device_try_acquire(up->cons))
cpu_relax();
}
/* Only for internal port lock wrapper usage. */
static inline void __uart_port_nbcon_release(struct uart_port *up)
{
if (!__uart_port_using_nbcon(up))
return;
nbcon_device_release(up->cons);
}
/**
* uart_port_lock - Lock the UART port
* @up: Pointer to UART port structure
@ -632,6 +688,7 @@ static inline void uart_port_set_cons(struct uart_port *up, struct console *con)
static inline void uart_port_lock(struct uart_port *up)
{
spin_lock(&up->lock);
__uart_port_nbcon_acquire(up);
}
/**
@ -641,6 +698,7 @@ 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);
__uart_port_nbcon_acquire(up);
}
/**
@ -651,6 +709,7 @@ 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);
__uart_port_nbcon_acquire(up);
}
/**
@ -661,7 +720,15 @@ 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;
if (!__uart_port_nbcon_try_acquire(up)) {
spin_unlock(&up->lock);
return false;
}
return true;
}
/**
@ -673,7 +740,15 @@ 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;
if (!__uart_port_nbcon_try_acquire(up)) {
spin_unlock_irqrestore(&up->lock, *flags);
return false;
}
return true;
}
/**
@ -682,6 +757,7 @@ static inline bool uart_port_trylock_irqsave(struct uart_port *up, unsigned long
*/
static inline void uart_port_unlock(struct uart_port *up)
{
__uart_port_nbcon_release(up);
spin_unlock(&up->lock);
}
@ -691,6 +767,7 @@ static inline void uart_port_unlock(struct uart_port *up)
*/
static inline void uart_port_unlock_irq(struct uart_port *up)
{
__uart_port_nbcon_release(up);
spin_unlock_irq(&up->lock);
}
@ -701,6 +778,7 @@ 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)
{
__uart_port_nbcon_release(up);
spin_unlock_irqrestore(&up->lock, flags);
}