the lru is there to track least recently used messages so
we can evict them from the cache and refetch them again on
demand. for pop3 mailbox, which doesnt provide fetch routine,
the messages should never be put on the freelist.
The previous attempt to fix this problem (see changesets b32199e0f90a
and 00ae79a6ba50) caused all calls to cachefree to free the cached
message contents in addition to updating the LRU list. This causes
problems for the POP3 driver since it provides no fetch function; once
a message is evicted from the LRU cache, its contents is lost.
This time we fix cachefree to always update the LRU list but only free
the cached message contents if the driver provides a fetch function or
the force flag is set.
Some SD card readers are slow to unstall. We try to unstall them
in a loop if there's no SD card in there, but they're not stalled.
They're happily reporting that there's no SD card in them by giving
back the appropriate error code.
Skipping the unstall speeds up the retry loop, cutting the time spent
attaching the USB device at boot from multiple minutes to nearly instant.
Force the cacheclear operation in the LRU cache trimming loop in order
to guarantee that the cache becomes smaller with each iteration.
Without the force flag cacheclear is a no-op for mailboxes that do not
provide a fetch function, e.g. POP3.
because a client might not handle resize, rio would try to move ther
window offsceen after 750 ms. however, it does this by window name,
which could have been reassigned by another concurrent rio, causing the
wrong window to disappear.
now we always move the window offscreen before freeimage(). this way we
are sure to still have the right reference to the original window.
segclock() has to be called from hzclock(), otherwise
only processes running on cpu0 would catche the interrupt
and the time delta would be wrong.
lock the segment when allocating Seg->profile as
profile ctl might be issued from multiple processes.
Proc->debug qlock is not sufficient.
Seg->profile can never be freed or reallocated once
set as the timer interrupt accesses it without any
locking.
