#1006720 fontconfig: frozen in FcMutexLock, via FcCacheFindByAddr

Package:
libfontconfig1
Source:
fontconfig
Description:
generic font configuration library - runtime
Submitter:
Vincent Lefevre
Date:
2026-01-10 11:39:44 UTC
Severity:
important
Tags:
#1006720#5
Date:
2022-03-03 11:28:37 UTC
From:
To:
After increasing a gnuplot window to its full size, gnuplot hanged.
The backtrace shows that this happens in FcMutexLock, via
FcCacheFindByAddr:

#0  futex_wait (private=0, expected=2, futex_word=0x7ff95c05c630) at ../sysdeps/nptl/futex-internal.h:146
        __ret = -512
        err = <optimized out>
#1  __lll_lock_wait (futex=futex@entry=0x7ff95c05c630, private=0) at lowlevellock.c:52
#2  0x00007ff96adcefe3 in __GI___pthread_mutex_lock (mutex=0x7ff95c05c630) at ../nptl/pthread_mutex_lock.c:80
        __futex = 0x7ff95c05c630
        type = <optimized out>
        __PRETTY_FUNCTION__ = "__pthread_mutex_lock"
        id = <optimized out>
#3  0x00007ff96ab0d547 in FcMutexLock (m=<optimized out>) at ./src/fcmutex.h:122
        lock = <optimized out>
#4  0x00007ff96ab0e59e in FcCacheFindByAddr (object=0x7ff96cc73210) at ./src/fccache.c:663
        ret = <optimized out>
        skip = <optimized out>
#5  FcCacheObjectReference (object=0x7ff96cc73210) at ./src/fccache.c:750
        skip = <optimized out>
#6  0x00007ff96ab27c08 in IA__FcPatternReference (p=<optimized out>) at ./src/fcpat.c:1232
#7  0x00007ff969be6959 in font_set_copy (fontset=<optimized out>) at ../pango/pangofc-fontmap.c:785
        copy = 0x55c53ac4b660
        i = <optimized out>
        td = 0x55c53ac445c0
        fontmap = <optimized out>
#8  thread_data_new (patterns=patterns@entry=0x55c53a797640) at ../pango/pangofc-fontmap.c:812
        td = 0x55c53ac445c0
        fontmap = <optimized out>
[...]

The full backtrace is attached.
#1006720#10
Date:
2022-03-03 12:13:50 UTC
From:
To:
This actually occurred in the library.

Note: I could not reproduce the issue yet.

But the fccache.c code looks wrong. I'm going to report the bug
upstream.
#1006720#23
Date:
2022-03-03 14:40:41 UTC
From:
To:
Control: forwarded -1 https://gitlab.freedesktop.org/fontconfig/fontconfig/-/issues/318

Actually I couldn't find anything in fccache.c that could cause this
issue.

Also, note that the freeze probably occurred before the resize
(but I noticed it only after the resize, as the contents were not
redrawn).
#1006720#30
Date:
2026-01-10 10:08:08 UTC
From:
To:
Es gibt eine Familienspende in Höhe von 1.850.000,00 USD von Cheng Charlie
Saephan. Bitte antworten Sie für weitere Informationen. Denken Sie daran,
Ihrer Familie und den Bedürftigen in Ihrer Umgebung Gutes zu tun.

Dies ist bereits der zweite Versuch, Sie zu erreichen. Bitte antworten Sie
für weitere Details.
#1006720#35
Date:
2026-01-10 10:08:08 UTC
From:
To:
Es gibt eine Familienspende in Höhe von 1.850.000,00 USD von Cheng Charlie
Saephan. Bitte antworten Sie für weitere Informationen. Denken Sie daran,
Ihrer Familie und den Bedürftigen in Ihrer Umgebung Gutes zu tun.

Dies ist bereits der zweite Versuch, Sie zu erreichen. Bitte antworten Sie
für weitere Details.