[PATCHSET v2 next 0/5] Add support for non-IPI task_work

[Jens Axboe <axboe@kernel.dk>]

Hi,

Unless we're using SQPOLL, any task_work queue will result in an IPI
to the target task unless it's running in the kernel already. This isn't
always needed, particularly not for the common case of not sharing the
ring. In certain workloads, this can provide a 5-10% improvement. Some
of this is due the cost of the IPI, and some from needlessly
interrupting the target task when the work could just get run when
completions are being waited for.

Patches 1..4 are prep patches, patch 5 is the actual change.

v2:
- Switch sq_flags to atomic_t and use atomic bitop helpers rather than
  add helpers using try_cmpxchg() for setting/clearing of flags.
  Suggested by Pavel.

-- 
Jens Axboe