Title should be: "ovs-rcu: Add ovsrcu_barrier." On Wed, May 25, 2022 at 3:36 AM Peng He <[email protected]> wrote: > > rcu_barrier will block the current thread until all the postponed
ovsrcu_barrier* > rcu job has been finished. it's like the OVS's version of > the kernel rcu_barrier() It's like a OVS version of the Linux kernel rcu_barrier(). > > Signed-off-by: Peng He <[email protected]> > Co-authored-by: Eelco Chaudron <[email protected]> > Signed-off-by: Eelco Chaudron <[email protected]> > --- > lib/ovs-rcu.c | 38 ++++++++++++++++++++++++++++++++++++++ > lib/ovs-rcu.h | 15 +++++++++++++++ > 2 files changed, 53 insertions(+) > > diff --git a/lib/ovs-rcu.c b/lib/ovs-rcu.c > index 1866bd308..86741f2b4 100644 > --- a/lib/ovs-rcu.c > +++ b/lib/ovs-rcu.c > @@ -444,3 +444,41 @@ ovsrcu_init_module(void) > ovsthread_once_done(&once); > } > } > + > +static void > +ovsrcu_barrier_func(void *seq_) > +{ > + struct seq *seq = (struct seq *) seq_; > + seq_change(seq); > +} > + > + One blank line is enough. > +/* Similar to the kernel rcu_barrier, ovsrcu_barrier waits for all > outstanding > + * RCU callbacks to complete. However, unlike the kernel rcu_barrier, which > + * might retrun immediately if there are no outstanding RCU callbacks, return* > + * this API will at least wait for a grace period. > + * > + * Another issue the caller might need to know it's that the barrier is just > + * for "one-shot", i.e. if inside some RCU callbacks, another RCU callback is > + * registered, this API only guarantees the first round of RCU callbacks have > + * been executed after it returns. to know is* that > + */ > +void > +ovsrcu_barrier(void) > +{ > + struct seq *seq = seq_create(); > + /* First let all threads flush their cbsets. */ > + ovsrcu_synchronize(); > + > + /* Then register a new cbset, ensure this cbset > + * is at the tail of the global list. */ > + uint64_t seqno = seq_read(seq); > + ovsrcu_postpone__(ovsrcu_barrier_func, (void *) seq); > + > + do { > + seq_wait(seq, seqno); > + poll_block(); > + } while (seqno == seq_read(seq)); > + > + seq_destroy(seq); > +} > diff --git a/lib/ovs-rcu.h b/lib/ovs-rcu.h > index ecc4c9201..32a49069e 100644 > --- a/lib/ovs-rcu.h > +++ b/lib/ovs-rcu.h > @@ -155,6 +155,19 @@ > * port_delete(id); > * } > * > + * Use ovsrcu_barrier() to wait for all the outstanding RCU callbacks to > + * finish. This is useful when you have to destroy some resources however > + * these resources are referenced in the outstanding RCU callbacks. > + * > + * void rcu_cb(void *A) { > + * Use_A_do_something(A); do_something() is enough. > + * } > + * > + * void destroy_A() { > + * ovsrcu_postpone(rcu_cb, A); // will use A later > + * ovsrcu_barrier(); // wait for rcu_cb done > + * do_destroy_A(); // free A > + * } In these comments, code snippets are indented with an additional level. IOW: + * Use ovsrcu_barrier() to wait for all the outstanding RCU callbacks to + * finish. This is useful when you have to destroy some resources however + * these resources are referenced in the outstanding RCU callbacks. + * + * void rcu_cb(void *A) { + * do_something(A); + * } + * + * void destroy_A() { + * ovsrcu_postpone(rcu_cb, A); // will use A later + * ovsrcu_barrier(); // wait for rcu_cb done + * do_destroy_A(); // free A + * } > */ > > #include "compiler.h" > @@ -310,4 +323,6 @@ void ovsrcu_synchronize(void); > > void ovsrcu_exit(void); > > +void ovsrcu_barrier(void); > + > #endif /* ovs-rcu.h */ > -- > 2.25.1 > Reviewed-by: David Marchand <[email protected]> I think we should have a unit test for this new part of the ovs-rcu API. -- David Marchand _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
