6.6-stable review patch. If anyone has any objections, please let me know.
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From: Bjorn Andersson bjorn.andersson@oss.qualcomm.com
commit a387e73fedd6307c0e194deaa53c42b153ff0bd6 upstream.
GLINK operates using pre-allocated buffers, aka intents, where incoming messages are aggregated before being passed up the stack. In the case that no suitable intents have been announced by the receiver, the sender can request an intent to be allocated.
The initial implementation of the response to such request dealt with two outcomes; granted allocations, and all other cases being considered -ECANCELLED (likely from "cancelling the operation as the remote is going down").
But on some channels intent allocation is not supported, instead the remote will pre-allocate and announce a fixed number of intents for the sender to use. If for such channels an rpmsg_send() is being invoked before any channels have been announced, an intent request will be issued and as this comes back rejected the call fails with -ECANCELED.
Given that this is reported in the same way as the remote being shut down, there's no way for the client to differentiate the two cases.
In line with the original GLINK design, change the return value to -EAGAIN for the case where the remote rejects an intent allocation request.
It's tempting to handle this case in the GLINK core, as we expect intents to show up in this case. But there's no way to distinguish between this case and a rejection for a too big allocation, nor is it possible to predict if a currently used (and seemingly suitable) intent will be returned for reuse or not. As such, returning the error to the client and allow it to react seems to be the only sensible solution.
In addition to this, commit 'c05dfce0b89e ("rpmsg: glink: Wait for intent, not just request ack")' changed the logic such that the code always wait for an intent request response and an intent. This works out in most cases, but in the event that an intent request is rejected and no further intent arrives (e.g. client asks for a too big intent), the code will stall for 10 seconds and then return -ETIMEDOUT; instead of a more suitable error.
This change also resulted in intent requests racing with the shutdown of the remote would be exposed to this same problem, unless some intent happens to arrive. A patch for this was developed and posted by Sarannya S [1], and has been incorporated here.
To summarize, the intent request can end in 4 ways: - Timeout, no response arrived => return -ETIMEDOUT - Abort TX, the edge is going away => return -ECANCELLED - Intent request was rejected => return -EAGAIN - Intent request was accepted, and an intent arrived => return 0
This patch was developed with input from Sarannya S, Deepak Kumar Singh, and Chris Lew.
[1] https://lore.kernel.org/all/20240925072328.1163183-1-quic_deesin@quicinc.com...
Fixes: c05dfce0b89e ("rpmsg: glink: Wait for intent, not just request ack") Cc: stable@vger.kernel.org Tested-by: Johan Hovold johan+linaro@kernel.org Signed-off-by: Bjorn Andersson bjorn.andersson@oss.qualcomm.com Reviewed-by: Chris Lew quic_clew@quicinc.com Link: https://lore.kernel.org/r/20241023-pmic-glink-ecancelled-v2-1-ebc268129407@o... Signed-off-by: Bjorn Andersson andersson@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/rpmsg/qcom_glink_native.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
--- a/drivers/rpmsg/qcom_glink_native.c +++ b/drivers/rpmsg/qcom_glink_native.c @@ -1354,14 +1354,18 @@ static int qcom_glink_request_intent(str goto unlock;
ret = wait_event_timeout(channel->intent_req_wq, - READ_ONCE(channel->intent_req_result) >= 0 && - READ_ONCE(channel->intent_received), + READ_ONCE(channel->intent_req_result) == 0 || + (READ_ONCE(channel->intent_req_result) > 0 && + READ_ONCE(channel->intent_received)) || + glink->abort_tx, 10 * HZ); if (!ret) { dev_err(glink->dev, "intent request timed out\n"); ret = -ETIMEDOUT; + } else if (glink->abort_tx) { + ret = -ECANCELED; } else { - ret = READ_ONCE(channel->intent_req_result) ? 0 : -ECANCELED; + ret = READ_ONCE(channel->intent_req_result) ? 0 : -EAGAIN; }
unlock: