Showing error 914

User: Jiri Slaby
Error type: Double Lock
Error type description: Some lock is locked twice unintentionally in a sequence
File location: block/blk-core.c
Line in file: 1241
Project: Linux Kernel
Project version: 2.6.28
Tools: Undetermined 1
Smatch (1.59)
Entered: 2012-02-27 21:22:42 UTC

Source: 

1211
1212        /* ELV_NO_MERGE: elevator says don't/can't merge. */
1213        default:
1214                ;
1215        }
1216
1217get_rq:
1218        /*
1219         * This sync check and mask will be re-done in init_request_from_bio(),
1220         * but we need to set it earlier to expose the sync flag to the
1221         * rq allocator and io schedulers.
1222         */
1223        rw_flags = bio_data_dir(bio);
1224        if (sync)
1225                rw_flags |= REQ_RW_SYNC;
1226
1227        /*
1228         * Grab a free request. This is might sleep but can not fail.
1229         * Returns with the queue unlocked.
1230         */
1231        req = get_request_wait(q, rw_flags, bio);
1232
1233        /*
1234         * After dropping the lock and possibly sleeping here, our request
1235         * may now be mergeable after it had proven unmergeable (above).
1236         * We don't worry about that case for efficiency. It won't happen
1237         * often, and the elevators are able to handle it.
1238         */
1239        init_request_from_bio(req, bio);
1240
1241        spin_lock_irq(q->queue_lock);
1242        if (test_bit(QUEUE_FLAG_SAME_COMP, &q->queue_flags) ||
1243            bio_flagged(bio, BIO_CPU_AFFINE))
1244                req->cpu = blk_cpu_to_group(smp_processor_id());
1245        if (elv_queue_empty(q))
1246                blk_plug_device(q);
1247        add_request(q, req);
1248out:
1249        if (sync)
1250                __generic_unplug_device(q);
1251        spin_unlock_irq(q->queue_lock);
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