Server crashes if logRotate destination file already exists after receiving a SIGUSR1.
For example if SIGUSR1 is sent twice during the same second the destination file will be the same and the server will crash.

Affected version:

2015-01-13T13:54:10.021+0000 [signalProcessingThread] db version v2.6.4
2015-01-13T13:54:10.021+0000 [signalProcessingThread] git version: 3a830be0eb92d772aa855ebb711ac91d658ee910
2015-01-13T13:54:10.021+0000 [signalProcessingThread] build info: Linux build7.nj1.10gen.cc 2.6.32-431.3.1.el6.x86_64 #1 SMP Fri Jan 3 21:39:27 UTC 2014 x86_64 BOOST_LIB_VERSION=1_49

The reported error is:

015-01-13T13:54:10.766+0000 [signalProcessingThread] warning: Rotating log file /data/log/mongodb/mongodb.log failed: FileRenameFailed Renaming file /data/log/mongodb/mongodb.log to /data/log/mongodb/mongodb.log.2015-01-13T13-54-10 failed; destination already exists
2015-01-13T13:54:10.766+0000 [signalProcessingThread] Fatal Assertion 16782
2015-01-13T13:54:10.769+0000 [signalProcessingThread] 0x11e6111 0x1187e49 0x116a97d 0x11e57cf 0x122aaa9 0x7fe544cbd182 0x7fe543fc238d
/usr/bin/mongod(_ZN5mongo15printStackTraceERSo+0x21) [0x11e6111]
/usr/bin/mongod(_ZN5mongo10logContextEPKc+0x159) [0x1187e49]
/usr/bin/mongod(_ZN5mongo13fassertFailedEi+0xcd) [0x116a97d]
/usr/bin/mongod() [0x11e57cf]
/usr/bin/mongod() [0x122aaa9]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x8182) [0x7fe544cbd182]
/lib/x86_64-linux-gnu/libc.so.6(clone+0x6d) [0x7fe543fc238d]
2015-01-13T13:54:10.769+0000 [signalProcessingThread]

***aborting after fassert() failure

2015-01-13T13:54:10.772+0000 [signalProcessingThread] SEVERE: Got signal: 6 (Aborted).
Backtrace:0x11e6111 0x11e54ee 0x7fe543efe000 0x7fe543efdf89 0x7fe543f01398 0x116a9ea 0x11e57cf 0x122aaa9 0x7fe544cbd182 0x7fe543fc238d
/usr/bin/mongod(_ZN5mongo15printStackTraceERSo+0x21) [0x11e6111]
/usr/bin/mongod() [0x11e54ee]
/lib/x86_64-linux-gnu/libc.so.6(+0x37000) [0x7fe543efe000]
/lib/x86_64-linux-gnu/libc.so.6(gsignal+0x39) [0x7fe543efdf89]
/lib/x86_64-linux-gnu/libc.so.6(abort+0x148) [0x7fe543f01398]
/usr/bin/mongod(_ZN5mongo13fassertFailedEi+0x13a) [0x116a9ea]
/usr/bin/mongod() [0x11e57cf]
/usr/bin/mongod() [0x122aaa9]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x8182) [0x7fe544cbd182]
/lib/x86_64-linux-gnu/libc.so.6(clone+0x6d) [0x7fe543fc238d]