CVSROOT: /cvs
Module name: src
Changes by: [email protected] 2014/09/21 19:04:58
Modified files:
sys/kern : subr_pool.c
sys/sys : pool.h
Log message:
rework the pool code to make the locking more obvious (to me at
least). after this i am confident that pools are mpsafe, ie, can
be called without the kernel biglock being held.
the page allocation and setup code has been split into four parts:
pool_p_alloc is called without any locks held to ask the pool_allocator
backend to get a page and page header and set up the item list.
pool_p_insert is called with the pool lock held to insert the newly
minted page on the pools internal free page list and update its
internal accounting.
once the pool has finished with a page it calls the following:
pool_p_remove is called with the pool lock help to take the now
unnecessary page off the free page list and uncount it.
pool_p_free is called without the pool lock and does a bunch of
checks to verify that the items arent corrupted and have all been
returned to the page before giving it back to the pool_allocator
to be freed.
instead of pool_do_get doing all the work for pool_get, it is now
only responsible for doing a single item allocation. if for any
reason it cant get an item, it just returns NULL. pool_get is now
responsible for checking if the allocation is allowed (according
to hi watermarks etc), and for potentially sleeping waiting for
resources if required.
sleeping for resources is now built on top of pool_requests, which
are modelled on how the scsi midlayer schedules access to scsibus
resources.
the pool code now calls pool_allocator backends inside its own
calls to KERNEL_LOCK and KERNEL_UNLOCK, so users of pools dont
have to hold biglock to call pool_get or pool_put.
tested by krw@ (who found a SMALL_KERNEL issue, thank you)
noone objected
