CVS log for src/sys/sys/module_hook.h

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sys/module_hook.h: remove CONSTCOND comment from do-while-0 loop

Lint doesn't need this comment anymore, as there is nothing surprising
or unusual about this idiom.

Merge changes from current as of 20200406

Eliminate per-hook duplication of common code as suggested by
(and with major contributions from) riastradh@

Welcome to 9.99.23

Rather than keeping a separate mutex, condvar, and pserialize for each
module hook, we can share a common set of synchronization structures.
This cuts the amount of cacheline_aligned data for these structures by
50%.

Note that we still have a per-hook localcount, since we need to count
individual references.

As discussed with riastradh@

Welcome to 9.99.22 !

Adapt to use the new atomic_* operations.  As discussed with
riastradh@ in private Email.

Sync with HEAD

file module_hook.h was added on branch phil-wifi on 2019-06-10 22:09:57 +0000

Rename the MODULE_*_HOOK() macros to MODULE_HOOK_*() as briefly
discussed on irc.

NFCI intended.

Ride the earlier kernel bump - it;s getting crowded.

Merge the [pgoyette-compat] branch

Improve a comment

Convert the macros for setting and unsetting a hook to generate
in-line code rather than using an intermediary hook##set routine.
Hooks are set and unset only in one place, so the intermediary
routine provides no benefit.  IMHO using the macro at the point-
of-call is more readable than using it elsewhere in the code and
then calling the generated intermediary routine (for which you
won't even find its declaration or definition unless you remember
to search for the HOOK_SET macro instead).

NFC intended, will verify with a bulk build and an atf test run.

Convert the MODULE_{,VOID_}HOOK_CALL macros to do everything in-line
rather than defining an intermediate hook##call function.  Almost
all of the hooks are called only once, and although we lose the
ability of doing things like

	if (MODULE_HOOK_CALL(...) == 0) ...

we simplify things quite a bit.  With this change, we no longer need
to have both declaration and definition macros, and the definition
no longer needs to have both prototype argument list and a "real"
argument list.

FWIW, the above if now needs to written as

	int ret;

	MODULE_HOOK_CALL(..., ret);
	if (ret == 0) ...

with appropriate use of braces {}.

No need to declare the hook_call() function for void hooks.  So
remove and simplify.

Don't restrict hooks to having only int or void types.  Pass the hook's
type to the various macros, as needed.

Allows us to reduce diffs to original in at least one or two places (we
no longer have to provide an additional parameter to the hook routine
for returning a non-int return value).

The return value of a hook is not necessarily an error code, so
rename the variable appropriately.

NFCI

Create a variant of the HOOK macros that handles hook routines of
type void, and use them where appropriate.

Remove the HOOK2 versions of the MODULE_HOOK macros.  There were
only a few uses, and using them led to some lack of clarity in the
code.  Instead, we now use two separate hooks, with names that
make it clear(er) what we're doing.

This also positions us to start unraveling some of the rtsock_50
mess, which will need (at least) five hooks.

Separate macro arguments with <comma><space> for readability.

Use private-namespace variable ``__hooked'' instead of ``hooked''

Also in the UNSET_HOOK2 case, release the mutex before destroying it.

Grab the mutex for UNSET_HOOK2 (fixed previously for UNSET_HOOK)

In MODULE_HOOK_CALL_DECL we don't need to provide the actual argument
list for calling the hook function, nor do we need to provide the
default value (for when the hook has not been set).

Use restricted namespace identifiers for variables within the code
generated by macro expansion.

Ooops - we need to grab the mutex before we can drain the localcount!

Rename sys/compat_hook.h --> sys/module_hook.h to more accurately
state its intended usage

file module_hook.h was initially added on branch pgoyette-compat.