David Marchand <[email protected]> 于2022年5月25日周三 19:27写道：
> 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. > OK. I am going to add it in test-rcu.c. Thanks for the review! > > > -- > David Marchand > > -- hepeng _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
