On 08/02/2017 12:54 PM, David Miller wrote:
And if this kind of thing matters to the user, they will have a software or hardware watchdog driver enabled to break out of this situation.
The problem is that the user is not going to expect that the EMAC can disable the nearby switch(es) when the kernel is hung and not rebooted quickly enough. Internally, this bug/feature has caused quite a bit of mayhem, so the problem is real. No cares about enabling flow control -- it just happens to be enabled on some systems where the switch agrees to it. So random individuals can't debug the hardware because suddenly the EMAC has gone haywire and disabled the local network.
Turning off flow control by default has so many negative ramifications and don't try to convince me that users will be "aware" of this and turn it back on.
What are the negative ramifications? It's practically impossible to overload the chip such that it can't process the incoming packets fast enough. I don't know of any real-world situation where the EMAC needs to transmit pause frames.
-- Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.
