From be14eb619108fa8b7120eb2c42d66d5f623ae10e Mon Sep 17 00:00:00 2001 From: Brian King Date: Fri, 10 Sep 2010 09:03:21 +0200 Subject: [PATCH] block: Range check cpu in blk_cpu_to_group While testing CPU DLPAR, the following problem was discovered. We were DLPAR removing the first CPU, which in this case was logical CPUs 0-3. CPUs 0-2 were already marked offline and we were in the process of offlining CPU 3. After marking the CPU inactive and offline in cpu_disable, but before the cpu was completely idle (cpu_die), we ended up in __make_request on CPU 3. There we looked at the topology map to see which CPU to complete the I/O on and found no CPUs in the cpu_sibling_map. This resulted in the block layer setting the completion cpu to be NR_CPUS, which then caused an oops when we tried to complete the I/O. Fix this by sanity checking the value we return from blk_cpu_to_group to be a valid cpu value. Signed-off-by: Brian King Signed-off-by: Jens Axboe --- block/blk.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/block/blk.h b/block/blk.h index 6e7dc87..d6b911a 100644 --- a/block/blk.h +++ b/block/blk.h @@ -142,14 +142,18 @@ static inline int queue_congestion_off_threshold(struct request_queue *q) static inline int blk_cpu_to_group(int cpu) { + int group = NR_CPUS; #ifdef CONFIG_SCHED_MC const struct cpumask *mask = cpu_coregroup_mask(cpu); - return cpumask_first(mask); + group = cpumask_first(mask); #elif defined(CONFIG_SCHED_SMT) - return cpumask_first(topology_thread_cpumask(cpu)); + group = cpumask_first(topology_thread_cpumask(cpu)); #else return cpu; #endif + if (likely(group < NR_CPUS)) + return group; + return cpu; } /* -- 2.7.4