Segmentation fault in "get_free_list () at arena.c:855"

[iainlane]

I think that's inside the libc.

A few of my asgen runs end when the generator segfaults :(.

Thread 355 (Thread 0x7fefcd7fa700 (LWP 12934)):
#0  get_free_list () at arena.c:855
#1  0x00007ffff54df58d in arena_get2 (avoid_arena=0x0, size=552) at arena.c:950
#2  __GI___libc_malloc (bytes=552) at malloc.c:2912
#3  0x00007ffff54c9c8d in __fopen_internal (filename=0x7ffff55eb11b "/etc/resolv.conf", mode=0x7ffff55e7f73 "rce",
    is32=1) at iofopen.c:69
#4  0x00007ffff54c9d2a in _IO_new_fopen (filename=<optimized out>, mode=<optimized out>) at iofopen.c:97
#5  0x00007ffff5582454 in __res_vinit (statp=0x7fefcd7fadb8, preinit=preinit@entry=0) at res_init.c:230
#6  0x00007ffff5582dd7 in __GI___res_ninit (statp=<optimized out>) at res_init.c:143
#7  0x00007ffff55841cd in __GI___res_maybe_init (resp=0x7fefcd7fadb8, preinit=preinit@entry=0) at res_libc.c:125
#8  0x00007ffff5546c08 in gaih_inet (name=name@entry=0x37aee40 "ftpmaster.internal", service=<optimized out>,
    req=req@entry=0x55c1090, pai=pai@entry=0x7fefcd7f8ca8, naddrs=naddrs@entry=0x7fefcd7f8ca4)
    at ../sysdeps/posix/getaddrinfo.c:819
#9  0x00007ffff554a4ae in __GI_getaddrinfo (name=<optimized out>, service=0x7fefcd7f8e40 "80", hints=0x55c1090,
    pai=0x7fefcd7f8df0) at ../sysdeps/posix/getaddrinfo.c:2417
#10 0x00007ffff7ba5887 in ?? () from /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#11 0x00007ffff7bb06ca in ?? () from /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#12 0x00007ffff7bade5b in ?? () from /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#13 0x00007ffff5c4a6fa in start_thread (arg=0x7fefcd7fa700) at pthread_create.c:333
#14 0x00007ffff5562b5d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
Thread 354 (Thread 0x7fefce7fc700 (LWP 12930)):
#0  __lll_lock_wait_private () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:95
#1  0x00007ffff54d99c4 in get_free_list () at arena.c:867
#2  0x00007ffff54df58d in arena_get2 (avoid_arena=0x0, size=552) at arena.c:950
#3  __GI___libc_malloc (bytes=552) at malloc.c:2912
#4  0x00007ffff54c9c8d in __fopen_internal (filename=0x7ffff55eb11b "/etc/resolv.conf", mode=0x7ffff55e7f73 "rce",
    is32=1) at iofopen.c:69
#5  0x00007ffff54c9d2a in _IO_new_fopen (filename=<optimized out>, mode=<optimized out>) at iofopen.c:97
#6  0x00007ffff5582454 in __res_vinit (statp=0x7fefce7fcdb8, preinit=preinit@entry=0) at res_init.c:230
#7  0x00007ffff5582dd7 in __GI___res_ninit (statp=<optimized out>) at res_init.c:143
#8  0x00007ffff55841cd in __GI___res_maybe_init (resp=0x7fefce7fcdb8, preinit=preinit@entry=0) at res_libc.c:125
#9  0x00007ffff5546c08 in gaih_inet (name=name@entry=0x37aee80 "ftpmaster.internal", service=<optimized out>,
    req=req@entry=0xa4c300, pai=pai@entry=0x7fefce7faca8, naddrs=naddrs@entry=0x7fefce7faca4)
    at ../sysdeps/posix/getaddrinfo.c:819
#10 0x00007ffff554a4ae in __GI_getaddrinfo (name=<optimized out>, service=0x7fefce7fae40 "80", hints=0xa4c300,
    pai=0x7fefce7fadf0) at ../sysdeps/posix/getaddrinfo.c:2417
#11 0x00007ffff7ba5887 in ?? () from /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#12 0x00007ffff7bb06ca in ?? () from /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#13 0x00007ffff7bade5b in ?? () from /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#14 0x00007ffff5c4a6fa in start_thread (arg=0x7fefce7fc700) at pthread_create.c:333
#15 0x00007ffff5562b5d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109

No debugging symbols for libcurl atm, sorry. But that's two threads in the same codepath.

I think it's called from this thread

Thread 1 (Thread 0x7ffff7fc87c0 (LWP 12527)):
#0  0x00007ffff5556e8d in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007ffff7ba2564 in ?? () from /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#2  0x00007ffff7b966ec in curl_easy_perform () from /usr/lib/x86_64-linux-gnu/libcurl-gnutls.so.4
#3  0x00000000005c288d in std.net.curl.Curl.perform(std.typecons.Flag!("throwOnError").Flag) (throwOnError=true,
    this=...) at ../../../../src/libphobos/src/std/net/curl.d:3808
#4  std.net.curl.HTTP.perform(std.typecons.Flag!("throwOnError").Flag) (this=...,
    throwOnError=throwOnError@entry=true) at ../../../../src/libphobos/src/std/net/curl.d:2280
#5  0x00000000004e4902 in utils.download(const(immutable(char)[]), ref std.stdio.File, const(uint)) (url=...,
    dest=..., retryCount=retryCount@entry=4) at source/utils.d:371
#6  0x00000000004e4a2f in utils.download(const(immutable(char)[]), ref std.stdio.File, const(uint)) (url=...,
    dest=..., retryCount=retryCount@entry=5) at source/utils.d:386
#7  0x00000000004e4ae3 in utils.getFileContents(const(immutable(char)[]), const(uint)) (path=...,
    retryCount=retryCount@entry=5) at source/utils.d:416
#8  0x00000000004e4ca7 in backends.debian.debpkgindex.DebianPackageIndex.findTranslations(const(immutable(char)[]), const(immutable(char)[])) (this=this@entry=0x7ffff7eced80, suite=..., section=...)
    at source/backends/debian/debpkgindex.d:78
#9  0x00000000004e6a26 in backends.debian.debpkgindex.DebianPackageIndex.loadPackageLongDescs(backends.debian.debpkg.DebPackage[immutable(char)[]], immutable(char)[], immutable(char)[]) (this=this@entry=0x7ffff7eced80, pkgs=...,
    suite=..., section=...) at source/backends/debian/debpkgindex.d:99
#10 0x00000000004e79cd in backends.debian.debpkgindex.DebianPackageIndex.loadPackages(immutable(char)[], immutable(char)[], immutable(char)[]) (this=0x7ffff7eced80, suite=..., section=..., arch=...)
    at source/backends/debian/debpkgindex.d:225
#11 0x00000000004e7b94 in backends.debian.debpkgindex.DebianPackageIndex.packagesFor(immutable(char)[], immutable(char)[], immutable(char)[]) (this=0x7ffff7eced80, suite=..., section=..., arch=...)
    at source/backends/debian/debpkgindex.d:234
#12 0x00000000004e7c89 in backends.ubuntu.ubupkgindex.UbuntuPackageIndex.packagesFor(immutable(char)[], immutable(char)[], immutable(char)[]) (this=0x7ffff7eced80, suite=..., section=..., arch=...)
    at source/backends/ubuntu/ubupkgindex.d:60
#13 0x00000000004ec834 in engine.Engine.seedContentsData(config.Suite, immutable(char)[], immutable(char)[]) (
    arch=..., section=..., suite=..., this=0x7ffff7ed07c0) at source/engine.d:177
#14 engine.Engine.run(immutable(char)[]) (this=<optimized out>, suite_name=...) at source/engine.d:481
#15 0x00000000004e45f0 in D main (args=...) at source/app.d:118

It looks like something is blowing up when trying to resolve a DNS name. curl is supposed to be thread safe, so hopefully it's not that. Any ideas?

[ximion]

Wtf... Which version of curl are you using? I wonder if curl can't handle the DNS setup of that machine...
I'll try something when I'm home, but I think thread-safety is not the issue here (or should not be it, unless this is a curl bug...)

[iainlane]

It's what we have in xenial, so 7.47.0-1ubuntu2.1.

Hmm, I found https://sourceware.org/bugzilla/show_bug.cgi?id=10652 (comment #12) - I'll try rebuilding with -pthread and seeing if that reduces the crashes.

[ximion]

That sounds promising!

[iainlane]

That didn't work, but FYI no crash or hang (#24) so far when built with ldc...

[ximion]

Oho! If it stays that way, we are likely experiencing some bug in GDC or the ancient DRuntime/Phobos GDC is using.
In that case, I wonder if we should block compilations with non-LDC compilers. But let's see if it stays working :)

[ximion]

I have never seen this, and apparently it also doesn't happen anymore... And since the code has evolved a lot since this was reported, I'll close the bug report. Please file a new one if this happens ever again (TBH, this looks like a GC bug that might have been fixed in GDC/DRuntime).