Messages in this thread Patch in this message | | | Date | Wed, 25 Sep 2013 14:18:04 +0200 | From | Mikael Pettersson <> | Subject | [REGRESSION][BISECTED] 3.12-rc "n_tty: Don't wait for buffer work in read() loop" patch breaks gcc's testsuite |
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With 3.12-rc[12] I see unexpected failures in gcc's Ada acats testsuite, e.g.
=== acats tests === FAIL: a83009b FAIL: c37209a FAIL: c45531e FAIL: c45614a FAIL: c67005d FAIL: c730a01 FAIL: c74302b FAIL: cc3004a FAIL: cd2a24j FAIL: cd2a53a FAIL: cxa3001 FAIL: cxf3a07 FAIL: cxf3a08
=== acats Summary === # of expected passes 2307 # of unexpected failures 13 Native configuration is x86_64-unknown-linux-gnu
The exact failures vary from run to run, but some failures always occur on my x86_64 machines, and all three open gcc branches (trunk, 4.8, 4.7) are affected. With a 3.11 kernel the acats testsuite is always clean.
A bisection identified:
From f95499c3030fe1bfad57745f2db1959c5b43dca8 Mon Sep 17 00:00:00 2001 From: Peter Hurley <peter@hurleysoftware.com> Date: Sat, 15 Jun 2013 13:14:29 +0000 Subject: n_tty: Don't wait for buffer work in read() loop
User-space read() can run concurrently with receiving from device; waiting for receive_buf() to complete is not required.
Signed-off-by: Peter Hurley <peter@hurleysoftware.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c index fe1c399..a6eea30 100644 --- a/drivers/tty/n_tty.c +++ b/drivers/tty/n_tty.c @@ -1724,7 +1724,6 @@ static inline int input_available_p(struct tty_struct *tty, int amt) { struct n_tty_data *ldata = tty->disc_data; - tty_flush_to_ldisc(tty); if (ldata->icanon && !L_EXTPROC(tty)) { if (ldata->canon_head != ldata->read_tail) return 1; as the culprit. Reverting that from 3.12-rc2 eliminates the acats failures and brings the gcc testsuite results to what one gets with 3.11.
I can't pretend to understand exactly what goes wrong, suffice it to say that the gcc testsuite harness uses a combination of shell, expect, and tcl. I suspect ptys are also involved.
To repeat, bootstrap a recent gcc 4.8 snapshot w/ ada in --enable-languages, then run the test suite with "make -j6 -k check; make mail-report.log". (Adjust -jN as appropriate, but -j6 is what I'm using on my quad-core i7s.)
Please consider reverting or fixing this patch.
/Mikael
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