Polling mode transactions wait for a reply busy-looping without holding a
spinlock, but currently the timeout checks are based only on elapsed time:
as a result we could hit a false positive whenever our busy-looping thread
is pre-empted and scheduled out for a time greater than the polling
timeout.
Change the checks at the end of the busy-loop to make sure that the polling
wasn't indeed successful or an out-of-order reply caused the polling to be
forcibly terminated.
Fixes: 31d2f803c19c ("firmware: arm_scmi: Add sync_cmds_completed_on_ret transport flag")
Reported-by: Huangjie <huangjie1663@xxxxxxxxxxxxxx>
Closes: https://lore.kernel.org/arm-scmi/20250123083323.2363749-1-jackhuang021@xxxxxxxxx/
Signed-off-by: Cristian Marussi <cristian.marussi@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 5.18.x
---
This fix got to be backported to 5.4/5.10./5.15 due to small changes in the
context
---
drivers/firmware/arm_scmi/driver.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 60050da54bf2..e6cf83950875 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -1248,7 +1248,8 @@ static void xfer_put(const struct scmi_protocol_handle *ph,
}
static bool scmi_xfer_done_no_timeout(struct scmi_chan_info *cinfo,
- struct scmi_xfer *xfer, ktime_t stop)
+ struct scmi_xfer *xfer, ktime_t stop,
+ bool *ooo)
{
struct scmi_info *info = handle_to_scmi_info(cinfo->handle);
@@ -1257,7 +1258,7 @@ static bool scmi_xfer_done_no_timeout(struct scmi_chan_info *cinfo,
* in case of out-of-order receptions of delayed responses
*/
return info->desc->ops->poll_done(cinfo, xfer) ||
- try_wait_for_completion(&xfer->done) ||
+ (*ooo = try_wait_for_completion(&xfer->done)) ||
ktime_after(ktime_get(), stop);
}
@@ -1274,15 +1275,17 @@ static int scmi_wait_for_reply(struct device *dev, const struct scmi_desc *desc,
* itself to support synchronous commands replies.
*/
if (!desc->sync_cmds_completed_on_ret) {
+ bool ooo = false;
+
/*
* Poll on xfer using transport provided .poll_done();
* assumes no completion interrupt was available.
*/
ktime_t stop = ktime_add_ms(ktime_get(), timeout_ms);
- spin_until_cond(scmi_xfer_done_no_timeout(cinfo,
- xfer, stop));
- if (ktime_after(ktime_get(), stop)) {
+ spin_until_cond(scmi_xfer_done_no_timeout(cinfo, xfer,
+ stop, &ooo));
+ if (!ooo && !info->desc->ops->poll_done(cinfo, xfer)) {
dev_err(dev,
"timed out in resp(caller: %pS) - polling\n",
(void *)_RET_IP_);
--
2.47.0
