I will add more info here: smp_mb() Similar to mb(), but only guarantees ordering between cores/processors within an SMP system. All memory accesses before the smp_mb() will be visible to all cores within the SMP system before any accesses after the smp_mb(). smp_rmb() Like smp_mb(), but only guarantees ordering between read accesses. smp_wmb() Like smp_mb(), but only guarantees ordering between write accesses. So these made me total confuse . Thanks 2011/12/9 trisha yad <trisha1march@xxxxxxxxx>: > Thanks, > > I got bit confuse with below statement: > This is from paper Memory access ordering Part 2 > SMP conditional barriers > The SMP conditional barriers are used to ensure a consistent view of > memory between different cores within a cache coherent SMP system. > When compiling a kernel without CONFIG_SMP, all SMP barriers are > converted into plain compiler barriers. > > 2011/12/9 卜弋天 <buyit@xxxxxxx>: >> Hi : >> >> memory barriers can not make order on other cpus, only the current >> cpu's order will be promised. >> >> >> >>> Date: Fri, 9 Dec 2011 12:54:40 +0530 >>> Subject: Memory barrier >>> From: trisha1march@xxxxxxxxx >>> To: Kernelnewbies@xxxxxxxxxxxxxxxxx >> >>> >>> Hi All, >>> >>> I need small clarification on memory barrier. >>> #define smp_mb() mb() >>> #define smp_rmb() rmb() >>> #define smp_wmb() wmb() >>> In case of SMP: >>> is smp_mb() or smp_rmb() make order on current CPU or all cpu's >>> >>> Thanks >>> >>> _______________________________________________ >>> Kernelnewbies mailing list >>> Kernelnewbies@xxxxxxxxxxxxxxxxx >>> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
