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serial: 8250: fix handle_irq locking

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The 8250 handle_irq callback is not just called from the interrupt
handler but also from a timer callback when polling (e.g. for ports
without an interrupt line). Consequently the callback must explicitly
disable interrupts to avoid a potential deadlock with another interrupt
in polled mode.

Add back an irqrestore-version of the sysrq port-unlock helper and use
it in the 8250 callbacks that need it.

Fixes: 75f4e830fa ("serial: do not restore interrupt state in sysrq helper")
Cc: stable@vger.kernel.org	# 5.13
Cc: Joel Stanley <joel@jms.id.au>
Cc: Andrew Jeffery <andrew@aj.id.au>
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20210714080427.28164-1-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2021-07-14 10:04:27 +02:00 • committed by Greg Kroah-Hartman
parent cc9ca4d958
commit 853a9ae29e
4 changed files with 33 additions and 6 deletions
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24
include/linux/serial_core.h
View file

@ -518,6 +518,25 @@ static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
if (sysrq_ch)
handle_sysrq(sysrq_ch);
}
static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port,
unsigned long flags)
{
int sysrq_ch;
if (!port->has_sysrq) {
spin_unlock_irqrestore(&port->lock, flags);
return;
}
sysrq_ch = port->sysrq_ch;
port->sysrq_ch = 0;
spin_unlock_irqrestore(&port->lock, flags);
if (sysrq_ch)
handle_sysrq(sysrq_ch);
}
#else /* CONFIG_MAGIC_SYSRQ_SERIAL */
static inline int uart_handle_sysrq_char(struct uart_port *port, unsigned int ch)
{
@ -531,6 +550,11 @@ static inline void uart_unlock_and_check_sysrq(struct uart_port *port)
{
spin_unlock(&port->lock);
}
static inline void uart_unlock_and_check_sysrq_irqrestore(struct uart_port *port,
unsigned long flags)
{
spin_unlock_irqrestore(&port->lock, flags);
}
#endif /* CONFIG_MAGIC_SYSRQ_SERIAL */
/*