kernel: Warn when an IRQ's affinity notifier gets overwritten

An IRQ affinity notifier getting overwritten can point to some annoying
issues which need to be resolved, like multiple pm_qos objects being
registered to the same IRQ. Print out a warning when this happens to aid
debugging.

Signed-off-by: Sultan Alsawaf <[email protected]>

wahoo_defconfig: Don't sync when entering suspend

Syncing can take a long time in some cases, and the risk of us losing
power or crashing while in suspend on a battery-backed device is very
low. Android also enters and exits suspend very frequently, which
exacerbates the cost.

Signed-off-by: Danny Lin <[email protected]>

cpuidle: Mark CPUs idle as late as possible to avoid unneeded IPIs

It isn't guaranteed a CPU will idle upon calling lpm_cpuidle_enter(),
since it could abort early at the need_resched() check. In this case,
it's possible for an IPI to be sent to this "idle" CPU needlessly, thus
wasting power. For the same reason, it's also wasteful to keep a CPU
marked idle even after it's woken up.

Reduce the window that CPUs are marked idle to as small as it can be in
order to improve power consumption.

Signed-off-by: Sultan Alsawaf <[email protected]>

mbcache: Speed up cache entry creation

In order to prevent redundant entry creation by racing against itself,
mb_cache_entry_create scans through a large hash-list of all current
entries in order to see if another allocation for the requested new
entry has been made. Furthermore, it allocates memory for a new entry
before scanning through this hash-list, which results in that allocated
memory being discarded when the requested new entry is already present.
This happens more than half the time.

Speed up cache entry creation by keeping a small linked list of
requested new entries in progress, and scanning through that first
instead of the large hash-list. Additionally, don't bother allocating
memory for a new entry until it's known that the allocated memory will
be used.

Signed-off-by: Sultan Alsawaf <[email protected]>