note in documentation another trigger for "Cannot allocate write+execute memory": systemd

[fche]

The readthedocs page that this write+execute callbacks message links people to mentions only selinux and a couple of other settings that can be responsible for this. One that I just came across today was different from these. On modern linux, systemd can install syscall filtering rules on services it supervises. The MemoryDenyWriteExecute= setting in systemd.exec(5) defaults on, and can quietly block this.

Please consider mentioning systemd and that setting on the readthedocs page.

[arigo]

Thanks! I've added a note to that page (pull #74). The readthedocs site might update now or later, I'm not sure.