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Re: [Libguestfs] [nbdkit PATCH 1/2] server: Propagate unexpected nbdkit failure with --run



On Mon, Sep 30, 2019 at 12:15:41PM -0500, Eric Blake wrote:
> diff --git a/server/captive.c b/server/captive.c
> index 90e42050..1606eb1a 100644
> --- a/server/captive.c
> +++ b/server/captive.c
> @@ -54,7 +54,7 @@ run_command (void)
>    FILE *fp;
>    char *cmd = NULL;
>    size_t len = 0;
> -  int r;
> +  int r, status;
>    pid_t pid;
> 
>    if (!run)
> @@ -135,20 +135,43 @@ run_command (void)
> 
>    if (pid > 0) {              /* Parent process is the run command. */
>      r = system (cmd);
> -    if (WIFEXITED (r))
> +    if (r == -1) {
> +      nbdkit_error ("failure to execute external command: %m");
> +      r = 1;

Although this is copying what the old code did, I wonder if we should
use r = EXIT_FAILURE here?

In any case the series is fine and I tested it, so:

ACK series

I don't know if you've noticed but because our tests use
MALLOC_PERTURB_ and because we have a race along the shutdown path,
some tests cause coredumps, eg:

$ make check
$ coredumpctl list
Mon 2019-09-30 21:20:45 BST  310684  1000  1000   6 present   /home/rjones/d/nbdkit/server/nbdkit
Mon 2019-09-30 21:21:07 BST  317022  1000  1000  11 present   /home/rjones/d/nbdkit/server/nbdkit
Mon 2019-09-30 21:21:08 BST  317217  1000  1000  11 present   /home/rjones/d/nbdkit/server/nbdkit
Mon 2019-09-30 21:21:16 BST  323530  1000  1000  11 present   /home/rjones/d/nbdkit/server/nbdkit
Mon 2019-09-30 21:21:17 BST  322363  1000  1000  11 present   /home/rjones/d/nbdkit/server/nbdkit
Mon 2019-09-30 21:21:19 BST  325833  1000  1000  11 present   /home/rjones/d/nbdkit/server/nbdkit
Mon 2019-09-30 21:21:22 BST  327989  1000  1000  11 present   /home/rjones/d/nbdkit/server/nbdkit
Mon 2019-09-30 21:21:22 BST  328290  1000  1000  11 present   /home/rjones/d/nbdkit/server/nbdkit
Mon 2019-09-30 21:21:23 BST  328520  1000  1000  11 present   /home/rjones/d/nbdkit/server/nbdkit
Mon 2019-09-30 21:21:24 BST  328914  1000  1000  11 present   /home/rjones/d/nbdkit/server/nbdkit
$ coredumpctl gdb
[...]
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x0000565098005718 in filter_finalize (b=0x5650a0693500, 
    conn=0x5650a0694940) at filters.c:440
440   return b->next->finalize (b->next, conn);
[Current thread is 1 (Thread 0x7fdacb08c700 (LWP 328918))]
Missing separate debuginfos, use: dnf debuginfo-install glibc-2.30-4.fc31.x86_64 gmp-6.1.2-10.fc31.x86_64 gnutls-3.6.9-1.fc31.x86_64 libffi-3.1-23.fc31.x86_64 libgcc-9.1.1-2.fc31.1.x86_64 libidn2-2.2.0-2.fc31.x86_64 libselinux-2.9-5.fc31.x86_64 libtasn1-4.14-2.fc31.x86_64 libunistring-0.9.10-6.fc31.x86_64 nettle-3.5.1-3.fc31.x86_64 p11-kit-0.23.16.1-2.fc31.x86_64 pcre2-10.33-12.fc31.x86_64
(gdb) bt
#0  0x0000565098005718 in filter_finalize (b=0x5650a0693500, 
    conn=0x5650a0694940) at filters.c:440
#1  0x000056509800316c in _handle_single_connection (sockout=<optimized out>, 
    sockin=<optimized out>) at connections.c:220
#2  handle_single_connection (sockin=<optimized out>, sockout=<optimized out>)
    at connections.c:239
#3  0x000056509800c7be in start_thread (datav=0x5650a06756f0) at sockets.c:276
#4  0x00007fdacb6dd4e2 in start_thread () from /lib64/libpthread.so.0
#5  0x00007fdacb60c643 in clone () from /lib64/libc.so.6

(This has happened for a long time and has nothing to do with this
patch series.)  I thought that this series might expose some of these
crashes and cause test failures, but it seems as if it does not.  So I
guess that these shutdown failures are not happening with --run, but
in test cleanup functions instead.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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