| Message ID | 20191124154334.15366-1-leo.yan@linaro.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] tty: serial: msm_serial: Fix lockup for sysrq and oops | expand |
On Sun, Nov 24, 2019 at 8:44 AM Leo Yan <leo.yan@linaro.org> wrote: > > As the commit 677fe555cbfb ("serial: imx: Fix recursive locking bug") > has mentioned the uart driver might cause recursive locking between > normal printing and the kernel debugging facilities (e.g. sysrq and > oops). In the commit it gave out suggestion for fixing recursive > locking issue: "The solution is to avoid locking in the sysrq case > and trylock in the oops_in_progress case." > > This patch follows the suggestion (also used the exactly same code with > other serial drivers, e.g. amba-pl011.c) to fix the recursive locking > issue, this can avoid stuck caused by deadlock and print out log for > sysrq and oops. > > Signed-off-by: Leo Yan <leo.yan@linaro.org> Shouldn't this patch have a Fixes tag? Was there a cover letter?
Hi Jeffrey, On Sun, Nov 24, 2019 at 04:00:21PM -0700, Jeffrey Hugo wrote: > On Sun, Nov 24, 2019 at 8:44 AM Leo Yan <leo.yan@linaro.org> wrote: > > > > As the commit 677fe555cbfb ("serial: imx: Fix recursive locking bug") > > has mentioned the uart driver might cause recursive locking between > > normal printing and the kernel debugging facilities (e.g. sysrq and > > oops). In the commit it gave out suggestion for fixing recursive > > locking issue: "The solution is to avoid locking in the sysrq case > > and trylock in the oops_in_progress case." > > > > This patch follows the suggestion (also used the exactly same code with > > other serial drivers, e.g. amba-pl011.c) to fix the recursive locking > > issue, this can avoid stuck caused by deadlock and print out log for > > sysrq and oops. > > > > Signed-off-by: Leo Yan <leo.yan@linaro.org> > > Shouldn't this patch have a Fixes tag? Will add fixes tag in next spin. > Was there a cover letter? Okay, I will add cover letter for patch set v2. Thanks for reviewing! Leo
diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c index 3657a24913fc..889538182e83 100644 --- a/drivers/tty/serial/msm_serial.c +++ b/drivers/tty/serial/msm_serial.c @@ -1576,6 +1576,7 @@ static void __msm_console_write(struct uart_port *port, const char *s, int num_newlines = 0; bool replaced = false; void __iomem *tf; + int locked = 1; if (is_uartdm) tf = port->membase + UARTDM_TF; @@ -1588,7 +1589,13 @@ static void __msm_console_write(struct uart_port *port, const char *s, num_newlines++; count += num_newlines; - spin_lock(&port->lock); + if (port->sysrq) + locked = 0; + else if (oops_in_progress) + locked = spin_trylock(&port->lock); + else + spin_lock(&port->lock); + if (is_uartdm) msm_reset_dm_count(port, count); @@ -1624,7 +1631,9 @@ static void __msm_console_write(struct uart_port *port, const char *s, iowrite32_rep(tf, buf, 1); i += num_chars; } - spin_unlock(&port->lock); + + if (locked) + spin_unlock(&port->lock); } static void msm_console_write(struct console *co, const char *s,
As the commit 677fe555cbfb ("serial: imx: Fix recursive locking bug") has mentioned the uart driver might cause recursive locking between normal printing and the kernel debugging facilities (e.g. sysrq and oops). In the commit it gave out suggestion for fixing recursive locking issue: "The solution is to avoid locking in the sysrq case and trylock in the oops_in_progress case." This patch follows the suggestion (also used the exactly same code with other serial drivers, e.g. amba-pl011.c) to fix the recursive locking issue, this can avoid stuck caused by deadlock and print out log for sysrq and oops. Signed-off-by: Leo Yan <leo.yan@linaro.org> --- drivers/tty/serial/msm_serial.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-)