[PATCH] serial: omap: Fix error handling in probe

[PATCH] serial: omap: Fix error handling in probe

[Semen Protsenko]

There is pm_qos_add_request() being executed on serial_omap_probe(),
which stores "&up->pm_qos_request" from omap-serial driver to
"pm_qos_array[PM_QOS_CPU_DMA_LATENCY]->constraints". If
serial_omap_probe() fails after pm_qos_add_request() (e.g. on
uart_add_one_port() call), pm_qos_array still keeping pm_qos_request
struct from omap-serial driver, which is not valid anymore (since driver
failed). This leads further to kernel crash on pm_qos_update_target(),
executing from some completely different driver.

We were observing this while trying to run audio playback while having
one of omap-serial driver instances failed on uart_add_one_port() call:
    Unable to handle kernel paging request at virtual address fffffffc
    Backtrace:
    (plist_add) from (pm_qos_update_target)
    (pm_qos_update_target) from (pm_qos_add_request)
    (pm_qos_add_request) from (snd_pcm_hw_params)
    (snd_pcm_hw_params) from (snd_pcm_common_ioctl1)
    (snd_pcm_common_ioctl1) from (snd_pcm_playback_ioctl1)
    (snd_pcm_playback_ioctl1) from (snd_pcm_playback_ioctl)
    (snd_pcm_playback_ioctl) from (do_vfs_ioctl)
    (do_vfs_ioctl) from (SyS_ioctl)
    (SyS_ioctl) from (ret_fast_syscall)

This patch adds pm_qos_remove_request() on fail path in
serial_omap_probe() in order to fix this issue. While at it, free the
wakeup settings on fail path as well, just like it's done in
serial_omap_remove().

Signed-off-by: Semen Protsenko <semen.protsenko@globallogic.com>
---
 drivers/tty/serial/omap-serial.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index d55714d..8d03486 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -1761,6 +1761,8 @@ static int serial_omap_probe(struct platform_device *pdev)
 err_add_port:
 	pm_runtime_put(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
+	pm_qos_remove_request(&up->pm_qos_request);
+	device_init_wakeup(up->dev, false);
 err_rs485:
 err_port_line:
 	dev_err(&pdev->dev, "[UART%d]: failure [%s]: %d\n",
-- 
1.7.9.5

Re: [PATCH] serial: omap: Fix error handling in probe

[Sam Protsenko]

v2 of this patch was sent (rebased on top of recent sources).

On Thu, Apr 30, 2015 at 6:28 PM, Semen Protsenko
<semen.protsenko@globallogic.com> wrote:
> There is pm_qos_add_request() being executed on serial_omap_probe(),
> which stores "&up->pm_qos_request" from omap-serial driver to
> "pm_qos_array[PM_QOS_CPU_DMA_LATENCY]->constraints". If
> serial_omap_probe() fails after pm_qos_add_request() (e.g. on
> uart_add_one_port() call), pm_qos_array still keeping pm_qos_request
> struct from omap-serial driver, which is not valid anymore (since driver
> failed). This leads further to kernel crash on pm_qos_update_target(),
> executing from some completely different driver.
>
> We were observing this while trying to run audio playback while having
> one of omap-serial driver instances failed on uart_add_one_port() call:
>     Unable to handle kernel paging request at virtual address fffffffc
>     Backtrace:
>     (plist_add) from (pm_qos_update_target)
>     (pm_qos_update_target) from (pm_qos_add_request)
>     (pm_qos_add_request) from (snd_pcm_hw_params)
>     (snd_pcm_hw_params) from (snd_pcm_common_ioctl1)
>     (snd_pcm_common_ioctl1) from (snd_pcm_playback_ioctl1)
>     (snd_pcm_playback_ioctl1) from (snd_pcm_playback_ioctl)
>     (snd_pcm_playback_ioctl) from (do_vfs_ioctl)
>     (do_vfs_ioctl) from (SyS_ioctl)
>     (SyS_ioctl) from (ret_fast_syscall)
>
> This patch adds pm_qos_remove_request() on fail path in
> serial_omap_probe() in order to fix this issue. While at it, free the
> wakeup settings on fail path as well, just like it's done in
> serial_omap_remove().
>
> Signed-off-by: Semen Protsenko <semen.protsenko@globallogic.com>
> ---
>  drivers/tty/serial/omap-serial.c |    2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
> index d55714d..8d03486 100644
> --- a/drivers/tty/serial/omap-serial.c
> +++ b/drivers/tty/serial/omap-serial.c
> @@ -1761,6 +1761,8 @@ static int serial_omap_probe(struct platform_device *pdev)
>  err_add_port:
>         pm_runtime_put(&pdev->dev);
>         pm_runtime_disable(&pdev->dev);
> +       pm_qos_remove_request(&up->pm_qos_request);
> +       device_init_wakeup(up->dev, false);
>  err_rs485:
>  err_port_line:
>         dev_err(&pdev->dev, "[UART%d]: failure [%s]: %d\n",
> --
> 1.7.9.5
>