|
|
|
|
|
|
by jeffbee
25 days ago
|
|
|
I can't help myself digging into the referenced source code. The membarrier syscall can fail to allocate, returning ENOMEM. The way Folly calls it, the program would abort. Which I guess is a fair strategy but it's good to know when your synchronization primitive is actually SynchronizeOrCrash. |
|
|
This is mentioned in the source comment, but not documented in the membarrier(2) manual page.
https://elixir.bootlin.com/linux/v7.1.2/source/kernel/sched/...
In reality... what is it allocating?
https://elixir.bootlin.com/linux/v7.1.2/source/kernel/sched/...
Ok, so it needs to allocate a cpumask (tiny) under some usages.
Similar requirement in other sites, e.g.: https://elixir.bootlin.com/linux/v7.1.2/source/kernel/sched/...
Depending on kernel config (e.g., !CONFIG_CPUMAKS_OFFSTACK), this allocation literally cannot fail:
https://elixir.bootlin.com/linux/v7.1.2/source/include/linux...
On OFFSTACK configs, it's merely a tiny heap allocation:
https://elixir.bootlin.com/linux/v7.1.2/source/lib/cpumask.c...
If this fails, your system is already hosed; program abort vs kernel lock up a few seconds later is probably immaterial. I think folly's choice to abort is a reasonable one.