5 ms·
5GHz WiFi has more bandwidth than 2.4GHz, so typically will involve larger IO buffers in the driver, which could easily be enough to expose a memory scribbler (
by abainbridge 7y ago
5GHz WiFi has more bandwidth than 2.4GHz, so typically will involve larger IO buffers in the driver, which could easily be enough to expose a memory scribbler (I imagine there's a bunch of other features that are enabled/disabled by the frequency band switch too). However, I think
asdfasgasdgasdg's answer is the correct reason not to suspect a memory scribbler - ie a memory scribbler would cause the driver to crash/fail and the kernel would log a message.
- StavrosK 7y agoBut 5 GHz doesn't fail, only 2.4 GHz does.
- wolfgke 7y agoThis is exactly abainbridge's point.
- StavrosK 7y agoHow do you mean? > 5GHz WiFi has more bandwidth than 2.4GHz, so typically will involve larger IO buffers in the driver, which could easily be enough to expose a memory scribbler He's saying 5 GHz will expose the scribbler, and the opposite is happening, only 2.4 GHz fails.
- abainbridge 7y ago@StavrosK Thanks for wading in in my defence, but I had actually mis-understood the situation :-) Although, if my theory that the IO buffers are different sizes is true, then that could perturb memory layout enough to expose/hide the bug in either direction.
- StavrosK 7y agoHaha, I was actually the attacker in this instance :) I do agree that the different IO buffers might hide the bug in one instance, but I think this is just plain old RF noise.
- abainbridge 7y ago> Haha, I was actually the attacker in this instance :) I need more sleep.
- deleted 7y ago[deleted]
- londons_explore 7y agoRemember the Pi has an odd architecture and all the IO passes through the GPU. The GPU doesn't log human readable messages anywhere. There's a good chance the GPU did log a crash or failure, but only broadcoms engineers can see it.
- abainbridge 7y agoEr, really, wow. I didn't know that. Can you point me at some more info for that? Surely the GPIOs don't go via the GPU.
- londons_explore 7y agoIt's a BCM2711, and the datasheet is NDA only - typical Broadcom! The VideoCore (Broadcoms GPU) is the main processor on the thing, and the cluster of ARM cores that run Linux are more of a coprocessor which can only see some of RAM.