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Date: Wed, 26 Oct 2011 10:42:26 +0530 From: Tiju Jacob <jacobtiju@...il.com> To: linux-kernel@...r.kernel.org Subject: Multi-partition block layer behaviour Hi All, We are trying to run fsstress tests on ext4 filesystem with linux-3.0.4 on nand flash with our proprietary driver. The test runs successfully when run on single partition but fails when run on multiple partitions with the bug "BUG: scheduling while atomic: fsstress.fork_n/498/0x00000002". Analysis: 1. When an I/O request is made to the filesystem, process 'A' acquires a mutex FS lock and a mutex block driver lock. 2. Process 'B' tries to acquire the mutex FS lock, which is not available. Hence, it goes to sleep. Due to the new plugging mechanism, before going to sleep, shcedule() is invoked which disables preemption and the context becomes atomic. In schedule(), the newly added blk_flush_plug_list() is invoked which unplugs the block driver. 3) During unplug operation the block driver tries to acquire the mutex lock which fails, because the lock was held by process 'A'. Previous invocation of scheudle() in step 2 has already made the context as atomic, hence the error "Schedule while atomic" occured. Please recommend us on how to handle this situation. Thanks in advance. --TJ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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