[mapserver-dev] Fwd: mapserver deadlock on signal

[Lauri]

Hi

There is a bug in how mapserver handles USR1 and TERM signals when
used in fastcgi mode.
msCleanupOnSignal calls msCleanup, which calls gdFontCacheShutdown
which tries to acquire a mutex that can already be locked, deadlocking
the process.

A sample stack trace showing the symptoms:
Process 12533 attached - interrupt to quit
futex(0x7ffdcb1b7d80, FUTEX_WAIT_PRIVATE, 2, NULL

(gdb) bt
#0  0x00007fdf9ec99be4 in __lll_lock_wait () from /lib/libpthread.so.0
#1  0x00007fdf9ec950e9 in _L_lock_953 () from /lib/libpthread.so.0
#2  0x00007fdf9ec94f0b in pthread_mutex_lock () from /lib/libpthread.so.0
#3  0x00007fdfa19edf1a in gdFontCacheShutdown () from /usr/lib/libgd.so.2
#4  0x000000000047e890 in msCleanup ()
#5  0x000000000044b4d0 in msCleanupOnSignal ()
#6  <signal handler called>
#7  0x00007fdfa154b538 in TT_RunIns () from /usr/lib/libfreetype.so.6
#8  0x00007fdfa1546073 in ?? () from /usr/lib/libfreetype.so.6
#9  0x00007fdfa154edc1 in ?? () from /usr/lib/libfreetype.so.6
#10 0x00007fdfa154f47d in ?? () from /usr/lib/libfreetype.so.6
#11 0x00007fdfa153b4aa in FT_Load_Glyph () from /usr/lib/libfreetype.so.6
#12 0x00007fdfa19eccb3 in gdImageStringFTEx () from /usr/lib/libgd.so.2
#13 0x00007fdfa19ed89b in gdImageStringFT () from /usr/lib/libgd.so.2
#14 0x00000000004cd151 in msDrawTextLineGD ()
#15 0x000000000057de7e in msDrawTextLine ()
#16 0x00000000004b8286 in msDrawLabelCache ()
#17 0x00000000004ad595 in msDrawMap ()
#18 0x00000000005a6aea in msWMSGetMap ()
#19 0x00000000005aa52d in msWMSDispatch ()
#20 0x000000000050ce91 in msOWSDispatch ()
#21 0x000000000044b8b8 in main ()

Patch for this problem is attached.

Lauri Nõmme
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