Re: [PATCH v2] serial: stm32: optimize spin lock usage
From: Johan Hovold <johan@kernel.org>
Date: 2021-04-12 13:08:24
Also in:
linux-serial, lkml, oe-kbuild-all
On Mon, Apr 12, 2021 at 05:31:38PM +0800, dillon.minfei@gmail.com wrote:
From: dillon min <redacted> To avoid potential deadlock in spin_lock usage, use spin_lock_irqsave, spin_trylock_irqsave(), spin_unlock_irqrestore() in process context.
This doesn't make much sense as console_write can be called in any context. And where's the deadlock you claim to be fixing here?
quoted hunk ↗ jump to hunk
remove unused local_irq_save/restore call. Cc: Alexandre Torgue <alexandre.torgue@foss.st.com> Cc: Maxime Coquelin <mcoquelin.stm32@gmail.com> Cc: Gerald Baeza <redacted> Cc: Erwan Le Ray <redacted> Reported-by: kernel test robot <redacted> Signed-off-by: dillon min <redacted> --- v2: remove unused code from stm32_usart_threaded_interrupt() according from Greg's review. drivers/tty/serial/stm32-usart.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-)diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c index b3675cf25a69..b1ba5e36e36e 100644 --- a/drivers/tty/serial/stm32-usart.c +++ b/drivers/tty/serial/stm32-usart.c@@ -1354,13 +1354,12 @@ static void stm32_usart_console_write(struct console *co, const char *s, u32 old_cr1, new_cr1; int locked = 1; - local_irq_save(flags); if (port->sysrq) locked = 0; else if (oops_in_progress) - locked = spin_trylock(&port->lock); + locked = spin_trylock_irqsave(&port->lock, flags); else - spin_lock(&port->lock); + spin_lock_irqsave(&port->lock, flags); /* Save and disable interrupts, enable the transmitter */ old_cr1 = readl_relaxed(port->membase + ofs->cr1);@@ -1374,8 +1373,7 @@ static void stm32_usart_console_write(struct console *co, const char *s, writel_relaxed(old_cr1, port->membase + ofs->cr1); if (locked) - spin_unlock(&port->lock); - local_irq_restore(flags); + spin_unlock_irqrestore(&port->lock, flags); } static int stm32_usart_console_setup(struct console *co, char *options)
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