Messages in this thread | | | Date | Sun, 17 Sep 2017 16:05:09 -0700 | From | "Paul E. McKenney" <> | Subject | Memory-ordering recipes |
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Hello!
The topic of memory-ordering recipes came up at the Linux Plumbers Conference microconference on Friday, so I thought that I should summarize what is currently "out there":
1. memory-barriers.txt: A bit rambling and diffuse for a recipes document.
2. https://www.kernel.org/pub/linux/kernel/people/paulmck/LWNLinuxMM/Examples.html Many of the examples are on-point, but this is aimed more at understanding the memory model than at an organized set of recipes.
3. https://www.kernel.org/pub/linux/kernel/people/paulmck/LWNLinuxMM/Examples.html Slides 15-20. Again, some of the litmus tests are on-point, but the focus is more on understanding the memory model than on an organized set of recipes.
So what litmus tests are needed? Here is my initial set:
1. Release-acquire chains, AKA ISA2, Z6.2, LB, and 3.LB
Lots of variety here, can in some cases substitute:
a. READ_ONCE() for smp_load_acquire() b. WRITE_ONCE() for smp_store_release() c. Dependencies for both smp_load_acquire() and smp_store_release(). d. smp_wmb() for smp_store_release() in first thread of ISA2 and Z6.2. e. smp_rmb() for smp_load_acquire() in last thread of ISA2.
2. MP (see test6.pdf for nickname translation)
a. smp_store_release() / smp_load_acquire() b. rcu_assign_pointer() / rcu_dereference() c. smp_wmb() / smp_rmb() d. Replacing either of the above with smp_mb()
3. SB
a. smp_mb(), as in lockless wait-wakeup coordination. And as in sys_membarrier()-scheduler coordination, for that matter.
Others?
Thanx, Paul
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