> Paul E. McKenney wrote:I used the smp_wmb() functions. I noted a couple of things. a) some of these macros just emit __asm__ __volatile__ into the code so why not just say "volatile" to begin with b) smp_wmb() in some cases worked and in other cases jut optimized away the global reference. c) I can go back and break the code again by inserting them and building broken assembler d) I ave been doing hardware and software design since the early 1980;s, I invented SMP affinity scheduling, and yes, I understand barriers and this concept of instruction score-boarding and optimization very well -- its not an excuse for a busted C compiler. It did not break all the places in the code, but broke enough for SMP to lock up and fail, It turned global variables into local variables. If you want me to reproduce this I can but it will have to wait til this evening because I have some product releases to get out the door at Omega 8 today. It's simple to reproduce. Take away the volatile declaration for the rlock_t structure in mdb-ia32.c (rlock_t debug_lock) in all code references and watch the thing lock up in SMP with multiple processors in the debugger each stuck with their own local copy of debug_lock. The barrier functions do not appear to work in all cases. Jeff --
| Hiten Pandya | Re: up? (emacs docbook xml ide) |
| David Newall | Re: Slow DOWN, please!!! |
| Greg KH | Re: [Ksummit-2008-discuss] Fixing the Kernel Janitors project |
| James Morris | Re: LSM conversion to static interface |
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| Gerrit Renker | [PATCH 0/37] dccp: Feature negotiation - last call for comments |
| Jarek Poplawski | [PATCH] pkt_sched: Destroy gen estimators under rtnl_lock(). |
| David Miller | Re: [BUG] New Kernel Bugs |
