Nick Piggin wrote:
If you want to ensure you always only modify host->removed from under
the spinlock, it would be enforcable by introducing an accessor function
and doing a BUG_ON(!spin_is_locked()) in there.
If you just want to ensure that host->removed is 0 at this point, you
shouldn't need any spinlocks AFAIKS... that way you can probably afford
to move it out from CONFIG_MMC_DEBUG and get wider testing.
The host->removed member is only used for this simple test. It is set in
mmc_host_remove() to indicate that the removal process has begun. At
this point it is invalid to call mmc_detect_change() (the place this
patch fixes). So the spinlocks are mostly there so that things are
properly ordered when we go SMP. Some creative barriers would probably
work as well, but I find spinlocks more "normal" and hence more readable.