On Tue, Apr 01, 2014 at 09:49:53AM +0530, ratheesh kannoth wrote: > Suppose in smp machine, if bottom half is executed by cpu #1 and > the userspace process is pinned to cpu #2. How can the spin lock > acuquired info ( lock value ) will be reflected to cpu #2 ( if cpu > #2 has already acquired and released the lock value and the lock value > is stored in a cpu #2 data cache. so if cpu #1 acquire it , cpu#2 > will read the cache value which says it is free). I could see that > spin_lock_t is not a volatile value also. volatile is a construct from C-language standard and does not help that much with syncing to CPUs. (Specific for Intel processors, now) If you read the beginning of Chapter 8 <http://www.intel.com/content/dam/www/public/us/en/documents/manuals/64-ia-32-architectures-software-developer-system-programming-manual-325384.pdf> then lookup ticket spinlocks and then revisit the spin_lock implementation it should get clear. Have fun, Hannes -- To unsubscribe from this list: send the line "unsubscribe netfilter" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
