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...I think we need some benchmarks. -- Michael -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: not available URL: <http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20140915/bdcf57a0/attachment-0001.sig>

...I think we need some benchmarks. -- Michael -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: not available URL: <http://lists.linuxfoundation.org/pipermail/virtualization/attachments/20140915/bdcf57a0/attachment-0001.sig>

If we read hwrng by long-running dd process, it takes too much cpu time and almost hold the mutex lock. When we check hwrng attributes from sysfs by cat, it gets stuck in waiting the lock releaseing. The problem can only be reproduced with non-smp guest with slow backend. This patchset resolves the issue by changing rng_dev_read() to always schedule 10 jiffies after release mutex lock, then cat

If we read hwrng by long-running dd process, it takes too much cpu time and almost hold the mutex lock. When we check hwrng attributes from sysfs by cat, it gets stuck in waiting the lock releaseing. The problem can only be reproduced with non-smp guest with slow backend. This patchset resolves the issue by changing rng_dev_read() to always schedule 10 jiffies after release mutex lock, then cat