Re: [PATCH] Testsuite: Catch gdbserver socket listen errors

[Sergio Durigan Junior <sergiodj at redhat dot com>]

On Tuesday, February 26 2019, Alan Hayward wrote:

> [This is a replacement for the patch "gdbserver: Add option to ignore
> SO_REUSEADDR".  The issue is the same, but the root cause is different].
>
> When launching gdbserver, the testsuite checks for binding failure but
> does not check for failure to listen to socket error (which can happen
> due to another gdbserver binding to the socket at the same time).
>
> When this error occurs, the test will ignore the error and connect GDB
> to the failed port.  This may succeed and GDB will now be connected to
> the gdbserver from another test.  This eventually causes both tests to
> fail.
>
> When running the tests suite with native-gdbserver across many cores,
> this issue may happen once or twice, each causing random failures for
> two .exp testscripts.

I remember having to touch this code when I was implementing the IPv6
feature, and I think your patch makes perfect sense.  It LGTM, but I'm
not a global maintainer.

> Example gdb.log output for the failure:
>
> The testsuite sucessfully notices a failure to connect to port 2348.
> It launches again with port 2349, which also fails.  The testsuite
> ignores this error and uses gdb to connect to the port - which succeeds.
>
> spawn /work/build/gdb/testsuite/../gdbserver/gdbserver --once localhost:2348 /work/build/gdb/testsuite/outputs/gdb.ada/arrayidx/p^M
> Can't bind address: Address already in use.^M
> Exiting^M
> Port 2348 is already in use.
> spawn /work/build/gdb/testsuite/../gdbserver/gdbserver --once localhost:2349 /work/build/gdb/testsuite/outputs/gdb.ada/arrayidx/p^M
> Can't listen on socket: Address already in use.^M
> Exiting^M
> target remote localhost:2349^M
> Remote debugging using localhost:2349^M
> Reading /lib/ld-linux-aarch64.so.1 from remote target...^M
> warning: File transfers from remote targets can be slow. Use "set sysroot" to access files locally instead.^M
> Reading /lib/ld-linux-aarch64.so.1 from remote target...^M
> Reading symbols from target:/lib/ld-linux-aarch64.so.1...^M
> Reading /lib/ld-2.23.so from remote target...^M
> Reading /lib/.debug/ld-2.23.so from remote target...^M
> Reading /work/build/install/lib/debug//lib/ld-2.23.so from remote target...^M
> Reading /work/build/install/lib/debug/lib//ld-2.23.so from remote target...^M
> Reading target:/work/build/install/lib/debug/lib//ld-2.23.so from remote target...^M
> (No debugging symbols found in target:/lib/ld-linux-aarch64.so.1)^M
> 0x0000ffffbf6d2cc0 in ?? () from target:/lib/ld-linux-aarch64.so.1^M
> (gdb) continue^M
> Continuing.^M
> Reading /lib/aarch64-linux-gnu/libc.so.6 from remote target...^M
> Reading /lib/aarch64-linux-gnu/libc-2.23.so from remote target...^M
> Reading /lib/aarch64-linux-gnu/.debug/libc-2.23.so from remote target...^M
> Reading /work/build/install/lib/debug//lib/aarch64-linux-gnu/libc-2.23.so from remote target...^M
> Reading /work/build/install/lib/debug/lib/aarch64-linux-gnu//libc-2.23.so from remote target...^M
> Reading target:/work/build/install/lib/debug/lib/aarch64-linux-gnu//libc-2.23.so from remote target...^M
> [Inferior 1 (process 35351) exited normally]^M
> (gdb) FAIL: gdb.ada/arrayidx.exp: can't run to main
>
> Meanwhile, at the same time, in another test, gdbserver successfully
> connects to port 2349.  GDB then trys to connect to the port, but it
> times out because the GDB in the test above has already connected to it.
>
> spawn /work/build/gdb/testsuite/../gdbserver/gdbserver --once localhost:2348 /work/build/gdb/testsuite/outputs/gdb.ada/rdv_wait/foo^M
> Can't bind address: Address already in use.^M
> Exiting^M
> Port 2348 is already in use.
> spawn /work/build/gdb/testsuite/../gdbserver/gdbserver --once localhost:2349 /work/build/gdb/testsuite/outputs/gdb.ada/rdv_wait/foo^M
> Process /work/build/gdb/testsuite/outputs/gdb.ada/rdv_wait/foo created; pid = 65162^M
> Listening on port 2349^M
> Remote debugging from host 127.0.0.1, port 45154^M
> target remote localhost:2349^M
> localhost:2349: Connection timed out.^M
> (gdb) ^CQuit^M
> (gdb) task 2^M
> Cannot inspect Ada tasks when program is not running^M
>
> 2019-02-26  Alan Hayward  <alan.hayward@arm.com>
>
> 	* lib/gdbserver-support.exp (gdbserver_start): Check for listen
> 	failure.
> ---
>  gdb/testsuite/lib/gdbserver-support.exp | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gdb/testsuite/lib/gdbserver-support.exp b/gdb/testsuite/lib/gdbserver-support.exp
> index 05234c43bd..dbd885aa22 100644
> --- a/gdb/testsuite/lib/gdbserver-support.exp
> +++ b/gdb/testsuite/lib/gdbserver-support.exp
> @@ -317,7 +317,7 @@ proc gdbserver_start { options arguments } {
>  	    -timeout 120
>  	    -notransfer
>  	    -re "Listening on" { }
> -	    -re "Can't bind address: Address already in use\\.\r\n" {
> +	    -re "Can't (bind address|listen on socket): Address already in use\\.\r\n" {
>  		verbose -log "Port $portnum is already in use."
>  		if ![target_info exists gdb,socketport] {
>  		    # Bump the port number to avoid the conflict.
> -- 
> 2.17.2 (Apple Git-113)

-- 
Sergio
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