On Wed, Feb 05, 2014 at 11:47:17AM +0900, YAMAMOTO Takashi wrote: > > On Wed, Jan 15, 2014 at 12:41:20PM +0900, YAMAMOTO Takashi wrote: > >> Add a comment about implicit synchronization which > >> fat-rwlock seems to rely on. > >> > >> Signed-off-by: YAMAMOTO Takashi <yamam...@valinux.co.jp> > >> --- > >> lib/ovs-thread.h | 8 ++++++++ > >> 1 file changed, 8 insertions(+) > >> > >> diff --git a/lib/ovs-thread.h b/lib/ovs-thread.h > >> index 8cf2ecc..dab7510 100644 > >> --- a/lib/ovs-thread.h > >> +++ b/lib/ovs-thread.h > >> @@ -447,6 +447,14 @@ void xpthread_join(pthread_t, void **); > >> * Compared to pthread_key_t, ovsthread_key_t has the follow limitations: > >> * > >> * - Destructors must not access thread-specific data (via > >> ovsthread_key). > >> + * > >> + * Unlike pthread_key_t, this API implicitly serializes key removal > >> + * (ovsthread_key_delete) and thread exit. (destructor) > >> + * I.e. > >> + * - ovsthread_key_delete ensures the completion of destructors for > >> + * the key. > >> + * - Once ovsthread_key_delete completed, no destructors for the key > >> + * will be executed on thread exit. > >> */ > >> typedef struct ovsthread_key *ovsthread_key_t; > > > > I think I understand what you are saying, but I think that I would > > phrase it differently. Does the following express what you mean? > > > > diff --git a/lib/ovs-thread.c b/lib/ovs-thread.c > > index a20b2fd..18e524e 100644 > > --- a/lib/ovs-thread.c > > +++ b/lib/ovs-thread.c > > @@ -592,7 +592,8 @@ ovsthread_key_create(ovsthread_key_t *keyp, void > > (*destructor)(void *)) > > } > > > > /* Frees 'key'. The destructor supplied to ovsthread_key_create(), if > > any, is > > - * not called. > > + * not called. This function returns only after any running destructors > > for > > + * 'key' complete execution. > > 'running destructors' is not exact. > i believe pthread api allows for concurrent exiting threads to > start executing the destructor after pthread_key_delete completed. > but this ovsthread one doesn't. and fat-rwlock relies on it. > > i think it's better to say the difference explicitly as > it guarantees more than pthread while using similar-looking names. > i was confused when reading fat-rwlock.
Do you like the following version? --8<--------------------------cut here-------------------------->8-- From: Ben Pfaff <b...@nicira.com> Date: Thu, 6 Feb 2014 17:06:00 -0800 Subject: [PATCH] ovs-thread: Add a comment. Reported-by: YAMAMOTO Takashi <yamam...@valinux.co.jp> Signed-off-by: Ben Pfaff <b...@nicira.com> --- lib/ovs-thread.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/lib/ovs-thread.h b/lib/ovs-thread.h index 8cf2ecc..f031894 100644 --- a/lib/ovs-thread.h +++ b/lib/ovs-thread.h @@ -444,9 +444,15 @@ void xpthread_join(pthread_t, void **); * (by recompiling). Thus, one may more freely use this form of * thread-specific data. * - * Compared to pthread_key_t, ovsthread_key_t has the follow limitations: + * ovsthread_key_t also differs from pthread_key_t in the following ways: * * - Destructors must not access thread-specific data (via ovsthread_key). + * + * - The pthread_key_t API allows concurrently exiting threads to start + * executing the destructor after pthread_key_delete() returns. The + * ovsthread_key_t API guarantees that, when ovsthread_key_delete() + * returns, all destructors have returned and no new ones will start + * execution. */ typedef struct ovsthread_key *ovsthread_key_t; -- 1.7.10.4 _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
