On Wed, 2026-09-23 at 14:52 +0100, Gary Guo wrote:
On Wed Sep 23, 2026 at 2:31 PM BST, Markus Probst wrote:
On Wed, 2026-09-23 at 12:35 +0200, Greg Kroah-Hartman wrote:
On Sun, Sep 20, 2026 at 02:29:58PM +0000, Markus Probst wrote:
These functions will be used to simply the serdev rust abstraction. It also contributes to the fixing of 2 race conditions in the serdev rust abstraction.
Signed-off-by: Markus Probst markus.probst@posteo.de
drivers/tty/serdev/core.c | 50 ++++++++++++++++++++++++++++++++++++- drivers/tty/serdev/serdev-ttyport.c | 38 ++++++++++++++++++++++++++++ include/linux/serdev.h | 6 +++++ 3 files changed, 93 insertions(+), 1 deletion(-)
diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c index bab1b143b8a6..e8aa89e733bd 100644 --- a/drivers/tty/serdev/serdev-ttyport.c +++ b/drivers/tty/serdev/serdev-ttyport.c @@ -7,8 +7,10 @@ #include <linux/tty.h> #include <linux/tty_driver.h> #include <linux/poll.h> +#include "../tty.h" #define SERPORT_ACTIVE 1 +#define SERPORT_PAUSE_RX 2 struct serport { struct tty_port *port; @@ -32,6 +34,14 @@ static size_t ttyport_receive_buf(struct tty_port *port, const u8 *cp, if (!test_bit(SERPORT_ACTIVE, &serport->flags)) return 0;
- if (test_bit(SERPORT_PAUSE_RX, &serport->flags))
return 0;- /*
* Ensure writes by the driver are visible before allowing traffic to resume.*/- smp_mb__after_atomic();
This scares me. Why not use a real lock?
I can use locks to make it less "fragile". But I don't I think I need them.
WHat's the issue here, you need this to be "flushed" before this call:
- ret = serdev_controller_receive_buf(ctrl, cp, count);
here?
And you just tested a bit, you didn't set a bit, so what are you trying to ensure is written exactly?
This should be an acquire load operation (paired with the release store operation in `ttyport_resume_rx`).
Then you should use `test_bit_acquire`.
Ok. For some reason there is no equivalent `set_bit_release`.
However, this isn't sufficient because there's no synchronization between this bit test with the bit set inside pause_rx.
Will be replaced with a mutex in the next revision.
Thanks - Markus Probst
Best, Gary