+=======================================
The padata parallel execution mechanism
-Last updated for 2.6.36
+=======================================
+
+:Last updated: for 2.6.36
Padata is a mechanism by which the kernel can farm work out to be done in
parallel on multiple CPUs while retaining the ordering of tasks. It was
sufficiently general fashion that it could be put to other uses as well.
The first step in using padata is to set up a padata_instance structure for
-overall control of how tasks are to be run:
+overall control of how tasks are to be run::
#include <linux/padata.h>
a multithreaded queue, naturally.
To allocate a padata instance with the cpu_possible_mask for both
-cpumasks this helper function can be used:
+cpumasks this helper function can be used::
struct padata_instance *padata_alloc_possible(struct workqueue_struct *wq);
Once an offline CPU in the user supplied cpumask comes online, padata
is going to use it.
-There are functions for enabling and disabling the instance:
+There are functions for enabling and disabling the instance::
int padata_start(struct padata_instance *pinst);
void padata_stop(struct padata_instance *pinst);
padata_stop clears the flag and blocks until the padata instance
is unused.
-The list of CPUs to be used can be adjusted with these functions:
+The list of CPUs to be used can be adjusted with these functions::
int padata_set_cpumasks(struct padata_instance *pinst,
cpumask_var_t pcpumask,
remove and mask is one of PADATA_CPU_SERIAL, PADATA_CPU_PARALLEL.
If a user is interested in padata cpumask changes, he can register to
-the padata cpumask change notifier:
+the padata cpumask change notifier::
int padata_register_cpumask_notifier(struct padata_instance *pinst,
struct notifier_block *nblock);
-To unregister from that notifier:
+To unregister from that notifier::
int padata_unregister_cpumask_notifier(struct padata_instance *pinst,
struct notifier_block *nblock);
The padata cpumask change notifier notifies about changes of the usable
cpumasks, i.e. the subset of active CPUs in the user supplied cpumask.
-Padata calls the notifier chain with:
+Padata calls the notifier chain with::
blocking_notifier_call_chain(&pinst->cpumask_change_notifier,
notification_mask,
to a struct padata_cpumask that contains the new cpumask information.
Actually submitting work to the padata instance requires the creation of a
-padata_priv structure:
+padata_priv structure::
struct padata_priv {
/* Other stuff here... */
be called in the process of getting the work done as we will see
momentarily.
-The submission of work is done with:
+The submission of work is done with::
int padata_do_parallel(struct padata_instance *pinst,
struct padata_priv *padata, int cb_cpu);
outstanding, it should be prepared to be called again with a new job before
the previous one completes. When a task does complete, parallel() (or
whatever function actually finishes the job) should inform padata of the
-fact with a call to:
+fact with a call to::
void padata_do_serial(struct padata_priv *padata);
submitted.
The one remaining function in the padata API should be called to clean up
-when a padata instance is no longer needed:
+when a padata instance is no longer needed::
void padata_free(struct padata_instance *pinst);