[issue20924] openssl init 100% CPU utilization

bob bob report at bugs.python.org
Fri Mar 14 15:29:14 CET 2014


New submission from bob bob:

We have written a server on Python 2.7.6  that uses openssl 0.9.8y running on Windows box.

Time to time our server freezes utilizing 100% CPU on ssl_init (C routine). The following is the process stack:

0021ee80 10036d19 0176d259 00000000 00000013 msvcr90+0x3b35d

0021ee9c 10022a22 0021ef1c 0176d218 1001bf62 _ssl!init_ssl+0x33b59

0021ef74 10073920 0176a158 0177ba18 00952a78 _ssl!init_ssl+0x1f862

0021ef84 10001714 0176a158 0147b350 00000000 _ssl!init_ssl+0x70760

0021ef88 0176a158 0147b350 00000000 00952a78 _ssl+0x1714

0021ef8c 0147b350 00000000 00952a78 ffffffff 0x176a158

0021ef90 00000000 00952a78 ffffffff 100d3038 0x147b350

This problem occurs when client connects to our server using slow modem channel. In this case client sends duplicated SYN TCP packet. When second SYN packet arrives to the server after SYN_ACK server's packet we have a trouble. Like this trace from server side:

140 38.807410000   172.16.35.6  192.168.52.1  TCP  74  44697 > 20444 [SYN] Seq=0 Win=14600 Len=0 MSS=1314 SACK_PERM=1 TSval=495224007 TSecr=0 WS=16

141 38.807428000   192.168.52.1 172.16.35.6   TCP  78  20444 > 44697 [SYN, ACK] Seq=0 Ack=1 Win=16384 Len=0 MSS=1460 WS=1 TSval=0 TSecr=0 SACK_PERM=1

148 39.288557000   172.16.35.6  192.168.52.1  TCP  74  44697 > 20444 [SYN] Seq=0 Win=14600 Len=0 MSS=1314 SACK_PERM=1 TSval=495224257 TSecr=0 WS=16

----------
components: Library (Lib), Windows
messages: 213555
nosy: bob.bob
priority: normal
severity: normal
status: open
title: openssl init 100% CPU  utilization
type: resource usage
versions: Python 2.7

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue20924>
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