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From: Saubhik Mukherjee <saubhik.mukherjee@gmail.com>
To: gregkh@linuxfoundation.org, jirislaby@kernel.org
Cc: linux-serial@vger.kernel.org, ldv-project@linuxtesting.org,
	andrianov@ispras.ru
Subject: [question] Is it possible to remove an active port (without shutdown)?
Date: Fri, 11 Jun 2021 15:03:42 +0530	[thread overview]
Message-ID: <07b2ccfa-cf98-54a2-d03c-50507de06d52@gmail.com> (raw)

Consider the following events involving drivers/tty/serial/owl-uart.c:

Suppose the driver is registered, and the owl_uart_probe() was called.
Then uart_startup() can be called in serial core. This calls
owl_uart_startup() which registers the interrupt handler owl_uart_irq.

Now suppose uart_remove_one_port() in serial core is called. This
detaches port from the core. This calls owl_uart_release_port(port).
This writes NULL to port->membase after iounmap of port->membase from
port->dev.

During this point, an interrupt is triggered and the interrupt callback
owl_uart_irq() is called (parallel with uart_remove_one_port()). This
tries to read port->membase to send or receive chars (with spinlock on
port->lock). This introduces a race condition on port->membase.

QUESTION: Is it possible to remove an active port (without shutdown)?

             reply	other threads:[~2021-06-11  9:35 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-11  9:33 Saubhik Mukherjee [this message]
2021-06-11  9:47 ` [question] Is it possible to remove an active port (without shutdown)? Greg KH
2021-06-14  9:57   ` Saubhik Mukherjee
2021-06-14 10:01     ` Greg KH

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