Re: [RFC] [PATCH] Pre-emption control for userspace

[One Thousand Gnomes]

Obvious bug

| Usage model is a thread mmaps this file during initialization. It then
| writes a 1 to the mmap'd file after it grabs the lock in its critical
| section where it wants immunity from pre-emption.

You need to write it first or you can be pre-empted taking the lock
before asking for immunity.

Presumably you could equally use something to group tasks (say a control
group of some form) and implement voluntary pre-emption within the group
only when in user space. Ie they only pre-empt each other by yielding but
they can be pre-empted by other tasks outside the group ?

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