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[PATCH] ia64 cpuset + build_sched_domains() mangles structures
I've already sent this to the maintainers, and this is now being sent to a larger community audience. I have fixed a problem with the ia64 version of build_sched_domains(), but a similar fix still needs to be made to the generic build_sched_domains() in kernel/sched.c. The "dynamic sched domains" functionality has recently been merged into 2.6.13-rcN that sees the dynamic declaration of a cpu-exclusive (a.k.a. "isolated") cpuset and rebuilds the CPU Scheduler sched domains and sched groups to separate away the CPUs in this cpu-exclusive cpuset from the remainder of the non-isolated CPUs. This allows the non-isolated CPUs to completely ignore the isolated CPUs when doing load-balancing. Unfortunately, build_sched_domains() expects that a sched domain will include all the CPUs of each node in the domain, i.e., that no node will belong in both an isolated cpuset and a non-isolated cpuset. Declaring a cpuset that violates this presumption will produce flawed data structures and will oops the kernel. To trigger the problem (on a NUMA system with >1 CPUs per node): cd /dev/cpuset mkdir newcpuset cd newcpuset echo 0 >cpus echo 0 >mems echo 1 >cpu_exclusive I have fixed this shortcoming for ia64 NUMA (with multiple CPUs per node). A similar shortcoming exists in the generic build_sched_domains() (in kernel/sched.c) for NUMA, and that needs to be fixed also. The fix involves dynamically allocating sched_group_nodes[] and sched_group_allnodes[] for each invocation of build_sched_domains(), rather than using global arrays for these structures. Care must be taken to remember kmalloc() addresses so that arch_destroy_sched_domains() can properly kfree() the new dynamic structures. Signed-off-by:John Hawkes <hawkes@sgi.com> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Cc: Ingo Molnar <mingo@elte.hu> Cc: "Luck, Tony" <tony.luck@intel.com> Signed-off-by: