> -----Original Message----- > From: michi1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx [mailto:michi1@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx] > Sent: Saturday, February 07, 2015 1:29 AM > To: Jeff Haran > Cc: kernelnewbies@xxxxxxxxxxxxxxxxx > Subject: Re: Is writer starvation a potential problem with RCU? > > Hi! > > On 18:19 Fri 06 Feb , Jeff Haran wrote: > > I've read that the Linux implementation of read-write locks (rwlock_t) can suffer from so called "writer starvation", whereby threads > that take a read lock on a read-write lock can prevent threads attempting to take a write lock on the same read-write lock from ever > acquiring the lock because there is no queuing of the readers and writers. If the lock is held for read access, any subsequent reader > will get the lock even if a write lock attempt is already in progress. > > > > Does anybody happen to know whether or not RCU has a similar issue? > > Why should it have this issue? > > An RCU read is basically an atomic pointer read. One writer and multiple > readers can run concurrently. When the writer is finished, it updates the > atomic pointer. > > The issue you may need to worry about is freeing the memory of the old > pointer. This can only be done after all readers have finished (see > synchronize_rcu() and call_rcu()). Depending on what you do, you may see high > memory usage or writers which are blocked waiting for readers to finish. > > -Michi Thanks, Jeff Haran _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
