On Wed, Feb 16, 2022 at 03:08:58PM +0000, Phil Elwell wrote: > UART drivers are meant to use the port spinlock within certain > methods, to protect against reentrancy. The sc16is7xx driver does > very little locking, presumably because when added it triggers > "scheduling while atomic" errors. This is due to the use of mutexes > within the regmap abstraction layer, and the mutex implementation's > habit of sleeping the current thread while waiting for access. > Unfortunately this lack of interlocking can lead to corruption of > outbound data, which occurs when the buffer used for I2C transmission > is used simultaneously by two threads - a work queue thread running > sc16is7xx_tx_proc, and an IRQ thread in sc16is7xx_port_irq, both > of which can call sc16is7xx_handle_tx. > > An earlier patch added efr_lock, a mutex that controls access to the > EFR register. This mutex is already claimed in the IRQ handler, and > all that is required is to claim the same mutex in sc16is7xx_tx_proc. > > See: https://github.com/raspberrypi/linux/issues/4885 > > Signed-off-by: Phil Elwell <phil@xxxxxxxxxxxxxxx> > --- > drivers/tty/serial/sc16is7xx.c | 3 +++ > 1 file changed, 3 insertions(+) What commit id does this fix? thanks, greg k-h
