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fe89def79c
pch_uart_interrupt() takes priv->port.lock which leads to two recursive
spinlock calls if low_latency==1 or CONFIG_PREEMPT_RT_FULL=y (one
otherwise):
pch_uart_interrupt
spin_lock_irqsave(priv->port.lock, flags)
case PCH_UART_IID_RDR_TO (data ready)
handle_rx_to
push_rx
tty_port_tty_get
spin_lock_irqsave(&port->lock, flags) <--- already hold this lock
...
tty_flip_buffer_push
...
flush_to_ldisc
spin_lock_irqsave(&tty->buf.lock)
spin_lock_irqsave(&tty->buf.lock)
disc->ops->receive_buf(tty, char_buf)
n_tty_receive_buf
tty->ops->flush_chars()
uart_flush_chars
uart_start
spin_lock_irqsave(&port->lock) <--- already hold this lock
Avoid this by using a dedicated lock to protect the eg20t_port structure
and IO access to its membase. This is more consistent with the 8250
driver. Ensure priv->lock is always take prior to priv->port.lock when
taken at the same time.
V2: Remove inadvertent whitespace change.
V3: Account for oops_in_progress for the private lock in
pch_console_write().
Note: Like the 8250 driver, if a printk is introduced anywhere inside
the pch_console_write() critical section, the kernel will hang
on a recursive spinlock on the private lock. The oops case is
handled by using a trylock in the oops_in_progress case.
Signed-off-by: Darren Hart <dvhart@linux.intel.com>
CC: Tomoya MORINAGA <tomoya.rohm@gmail.com>
CC: Feng Tang <feng.tang@intel.com>
CC: Alexander Stein <alexander.stein@systec-electronic.com>
Acked-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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| .. | ||
| hvc | ||
| ipwireless | ||
| serial | ||
| vt | ||
| amiserial.c | ||
| bfin_jtag_comm.c | ||
| cyclades.c | ||
| ehv_bytechan.c | ||
| isicom.c | ||
| Kconfig | ||
| Makefile | ||
| moxa.c | ||
| moxa.h | ||
| mxser.c | ||
| mxser.h | ||
| n_gsm.c | ||
| n_hdlc.c | ||
| n_r3964.c | ||
| n_tracerouter.c | ||
| n_tracesink.c | ||
| n_tracesink.h | ||
| n_tty.c | ||
| nozomi.c | ||
| pty.c | ||
| rocket.c | ||
| rocket.h | ||
| rocket_int.h | ||
| synclink.c | ||
| synclink_gt.c | ||
| synclinkmp.c | ||
| sysrq.c | ||
| tty_audit.c | ||
| tty_buffer.c | ||
| tty_io.c | ||
| tty_ioctl.c | ||
| tty_ldisc.c | ||
| tty_mutex.c | ||
| tty_port.c | ||