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authorJulian Wiedmann2020-07-03 15:20:03 +0200
committerMartin K. Petersen2020-07-08 00:50:56 -0400
commitc3bfffa5ec6901f758160edfb046bdc56d89e8d2 (patch)
treee2aaadb89761b255669bd3234b1d95f8d6e632b7 /drivers/cpufreq/speedstep-lib.c
parent6bcb7c171a0ce0b0114aa088404e552b49d85576 (diff)
scsi: zfcp: Avoid benign overflow of the Request Queue's free-level
zfcp_qdio_send() and zfcp_qdio_int_req() run concurrently, adding and completing SBALs on the Request Queue. There's a theoretical race where zfcp_qdio_int_req() completes a number of SBALs & increments the queue's free-level _before_ zfcp_qdio_send() was able to decrement it. This can cause ->req_q_free to momentarily hold a value larger than QDIO_MAX_BUFFERS_PER_Q. Luckily zfcp_qdio_send() is always called under ->req_q_lock, and all readers of the free-level also take this lock. So we can trust that zfcp_qdio_send() will clean up such a temporary overflow before anyone can actually observe it. But it's still confusing and annoying to worry about. So adjust the code to avoid this race. Link: https://lore.kernel.org/r/7f61f59a1f8db270312e64644f9173b8f1ac895f.1593780621.git.bblock@linux.ibm.com Reviewed-by: Steffen Maier <maier@linux.ibm.com> Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com> Signed-off-by: Benjamin Block <bblock@linux.ibm.com> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/cpufreq/speedstep-lib.c')
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