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8250: fix possible deadlock between serial8250_handle_port() and serial8250_interrupt()

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Commit 40b36daa introduced possibility that serial8250_backup_timeout() ->
serial8250_handle_port() locks port.lock without disabling irqs, thus
allowing deadlock against interrupt handler (port.lock is acquired in
serial8250_interrupt()).

Spotted by lockdep.

Signed-off-by: Jiri Kosina <[email protected]>
Cc: Dave Jones <[email protected]>
Cc: Russell King <[email protected]>
Cc: Alex Williamson <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Jiri Kosina 2007-04-23 14:41:21 -07:00 • committed by Linus Torvalds
commit 4bf3631cdb
1 changed files with 3 additions and 2 deletions
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5
drivers/serial/8250.c
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@ -1334,8 +1334,9 @@ static inline void
serial8250_handle_port(struct uart_8250_port *up)
{
unsigned int status;
unsigned long flags;
spin_lock(&up->port.lock);
spin_lock_irqsave(&up->port.lock, flags);
status = serial_inp(up, UART_LSR);
@ -1347,7 +1348,7 @@ serial8250_handle_port(struct uart_8250_port *up)
if (status & UART_LSR_THRE)
transmit_chars(up);
spin_unlock(&up->port.lock);
spin_unlock_irqrestore(&up->port.lock, flags);
}
/*