Bug 17411 - SIGSEGV with font creation & disposing in multiple threads
Summary: SIGSEGV with font creation & disposing in multiple threads
Status: NEW
Alias: None
Product: Class Libraries
Classification: Mono
Component: System.Drawing ()
Version: 3.2.x
Hardware: PC Linux
: --- normal
Target Milestone: Untriaged
Assignee: Bugzilla
Depends on:
Reported: 2014-01-24 04:54 UTC by Russell van der Walt
Modified: 2014-02-12 21:40 UTC (History)
3 users (show)

Is this bug a regression?: ---
Last known good build:

Simple program to reproduce the issue (1.17 KB, text/plain)
2014-01-24 04:54 UTC, Russell van der Walt

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Description Russell van der Walt 2014-01-24 04:54:19 UTC
Created attachment 5909 [details]
Simple program to reproduce the issue

We're experiencing the following SIGSEGV's when creating fonts in multiple threads:

Native stacktrace:

        mono() [0x4ab6ed]
        mono() [0x501cef]
        mono() [0x420367]
        /lib/x86_64-linux-gnu/libpthread.so.0(+0xfcb0) [0x7f38ec478cb0]
        /usr/lib/x86_64-linux-gnu/libfontconfig.so.1(FcCharSetDestroy+0x4) [0x7f38db7402a4]
        /usr/lib/x86_64-linux-gnu/libfontconfig.so.1(+0x18599) [0x7f38db74d599]
        /usr/lib/x86_64-linux-gnu/libfontconfig.so.1(FcPatternDestroy+0x7f) [0x7f38db74d88f]
        /usr/local/lib/libgdiplus.so(GdipDeleteFontFamily+0x118) [0x7f38e8e74848]
        /usr/local/lib/libgdiplus.so(GdipDeleteFont+0x1c) [0x7f38e8e7523c]

Debug info from gdb:
Got a SIGSEGV while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.

Sometimes we get the following:

*** glibc detected *** mono: double free or corruption (fasttop): 0x00007f35e8003050 ***
Native stacktrace:

The error is caused by simply creating and disposing fonts in multiple threads with similar code to this (see attachment for full program):

using (var fFamily = new FontFamily("Arial")) {
    using (var f = new Font(fFamily, 10, FontStyle.Regular)) {


I have not been able to reproduce the error on 32bit architectures.

OS is Ubuntu 12.04 

root@ubuntu12043:~/test# mono -V
Mono JIT compiler version 3.2.3 (tarball Fri Jan 24 00:12:45 SAST 2014)
Copyright (C) 2002-2012 Novell, Inc, Xamarin Inc and Contributors. www.mono-project.com
        TLS:           __thread
        SIGSEGV:       altstack
        Notifications: epoll
        Architecture:  amd64
        Disabled:      none
        Misc:          softdebug
        LLVM:          supported, not enabled.
        GC:            sgen

I've confirmed the problem is also present in mono 2.10.9.
Comment 1 Zoltan Varga 2014-01-24 15:25:18 UTC
-> sys.drawing
Comment 2 Miguel de Icaza [MSFT] 2014-02-12 21:40:19 UTC
We likely did not add locking around the underlying primitives for some of the APIs in System.Drawing, will require a review.