Hello, On Mon, Nov 04, 2013 at 11:37:13PM +0000, Tim Chen wrote: > The following changes are made to enable mcs_spinlock.h file to be > widely included in other files without causing problem: > > 1) Include a number of prerequisite header files and define > arch_mutex_cpu_relax(), if not previously defined. > 2) Separate out mcs_spin_lock() into a mcs_spinlock.c file. > 3) Make mcs_spin_unlock() an inlined function. [...] > +void mcs_spin_lock(struct mcs_spinlock **lock, struct mcs_spinlock *node) > +{ > + struct mcs_spinlock *prev; > + > + /* Init node */ > + node->locked = 0; > + node->next = NULL; > + > + prev = xchg(lock, node); > + if (likely(prev == NULL)) { > + /* Lock acquired */ > + node->locked = 1; > + return; > + } > + ACCESS_ONCE(prev->next) = node; > + smp_wmb(); > + /* Wait until the lock holder passes the lock down */ > + while (!ACCESS_ONCE(node->locked)) > + arch_mutex_cpu_relax(); > +} You have the barrier in a different place than the version in the header file; is this intentional? Also, why is an smp_wmb() sufficient (as opposed to a full smp_mb()?). Are there restrictions on the types of access that can occur in the critical section? Will -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>