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Russ Anderson authored
Linux does not gracefully deal with multiple processors going through OS_MCA aa part of the same MCA event. The first cpu into OS_MCA grabs the ia64_mca_serialize lock. Subsequent cpus wait for that lock, preventing them from reporting in as rendezvoused. The first cpu waits 5 seconds then complains that all the cpus have not rendezvoused. The first cpu then handles its MCA and frees up all the rendezvoused cpus and releases the ia64_mca_serialize lock. One of the subsequent cpus going thought OS_MCA then gets the ia64_mca_serialize lock, waits another 5 seconds and then complains that none of the other cpus have rendezvoused. This patch allows multiple CPUs to gracefully go through OS_MCA. The first CPU into ia64_mca_handler() grabs a mca_count lock. Subsequent CPUs into ia64_mca_handler() are added to a list of cpus that need to go through OS_MCA (a bit set in mca_cpu), and report in as rendezvoused, and but spin waiting their turn. The first CPU sees everyone rendezvous, handles his MCA, wakes up one of the other CPUs waiting to process their MCA (by clearing one mca_cpu bit), and then waits for the other cpus to complete their MCA handling. The next CPU handles his MCA and the process repeats until all the CPUs have handled their MCA. When the last CPU has handled it's MCA, it sets monarch_cpu to -1, releasing all the CPUs. In testing this works more reliably and faster. Thanks to Keith Owens for suggesting numerous improvements to this code. Signed-off-by:
Russ Anderson <rja@sgi.com> Signed-off-by:
Tony Luck <tony.luck@intel.com>
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