On Tue, Apr 02, 2019 at 08:23:34AM -0700, Paul E. McKenney wrote:
On Tue, Apr 02, 2019 at 11:14:40AM -0400, Mathieu Desnoyers wrote:
> ----- On Apr 2, 2019, at 10:28 AM, paulmck paulmck(a)linux.ibm.com wrote:
> > Hello!
> > This series prohibits use of DEFINE_SRCU() and DEFINE_STATIC_SRCU()
> > by loadable modules. The reason for this prohibition is the fact
> > that using these two macros within modules requires that the size of
> > the reserved region be increased, which is not something we want to
> > be doing all that often. Instead, loadable modules should define an
> > srcu_struct and invoke init_srcu_struct() from their module_init function
> > and cleanup_srcu_struct() from their module_exit function. Note that
> > modules using call_srcu() will also need to invoke srcu_barrier() from
> > their module_exit function.
> This arbitrary API limitation seems weird.
> Isn't there a way to allow modules to use DEFINE_SRCU and DEFINE_STATIC_SRCU
> while implementing them with dynamic allocation under the hood ?
Although call_srcu() already has initialization hooks, some would
also be required in srcu_read_lock(), and I am concerned about adding
memory allocation at that point, especially given the possibility
of memory-allocation failure. And the possibility that the first
srcu_read_lock() happens in an interrupt handler or similar.
Or am I missing a trick here?
Which 'reserved region' are you referring to? Isn't this region also
used for non-module cases in which case the same problem applies to