mbox series

[0/9] Patch to fix glibc condition variable bug (BZ 25847)

Message ID 20230128021829.7990-1-malteskarupke@fastmail.fm (mailing list archive)
Headers
Series Patch to fix glibc condition variable bug (BZ 25847) |

Message

develop--- via Libc-alpha Jan. 28, 2023, 2:18 a.m. UTC 
  From: Malte Skarupke <malteskarupke@fastmail.fm>

The following emails are patches to fix the glibc condition variable bug,
BZ 25847.

The first patch is Frank Barrus' patch, as he submitted it on bugzilla.
Patch 2 fixes up comments and indentation, finishing the patch.
Further patches in the series do follow-up clean-up, like removing
unnecessary checks and unnecessary variables.

All of these patches are verified in TLA+ so that I am at least sure
that they don't introduce some similar issue. The condition variable
implementation also got a lot simpler as a result, so it is now much
easier to reason about, further increasing confidence.

The code for the TLA+ checking is here:
https://github.com/skarupke/glibc_tla_plus



Please note that this will probably be my last attempt to submit a
patch. I have submitted two series of patches before and was mostly
greeted with silence. If the same thing happens again, I'm going to give
up on glibc.


Frank Barrus (1):
  pthreads NPTL: lost wakeup fix 2

Malte Skarupke (8):
  nptl: Update comments and indentation for new condvar implementation
  nptl: Remove unnecessary catch-all-wake in condvar group switch
  nptl: Remove unnecessary quadruple check in pthread_cond_wait
  nptl: Remove g_refs from condition variables
  nptl: Use a single loop in pthread_cond_wait instaed of a nested loop
  nptl: Fix indentation
  nptl: rename __condvar_quiesce_and_switch_g1
  nptl: Use all of g1_start and g_signals

 nptl/pthread_cond_broadcast.c           |   8 +-
 nptl/pthread_cond_common.c              | 109 ++--------
 nptl/pthread_cond_signal.c              |  19 +-
 nptl/pthread_cond_wait.c                | 278 +++++-------------------
 nptl/tst-cond22.c                       |  12 +-
 sysdeps/nptl/bits/thread-shared-types.h |   4 +-
 sysdeps/nptl/pthread.h                  |   2 +-
 7 files changed, 100 insertions(+), 332 deletions(-)

Comments

Malte Skarupke Feb. 8, 2023, 2:48 a.m. UTC | #1 
Ping. I really think you want these changes. These are patches that fix the issue with no downsides. The code is clearer, performance better, and a really bad bug is fixed.
Sam James Feb. 8, 2023, 2:51 a.m. UTC | #2 
> On 8 Feb 2023, at 02:48, Malte Skarupke via Libc-alpha <libc-alpha@sourceware.org> wrote:
> 
> Ping. I really think you want these changes. These are patches that fix the issue with no downsides. The code is clearer, performance better, and a really bad bug is fixed.
> 

It's been a few days and your patch was noted in Monday's patch review. It looks like it's on Carlos' list to review
shortly.

> --
>  Malte Skarupke
>  malteskarupke@fastmail.fm
Malte Skarupke March 18, 2023, 12:08 p.m. UTC | #3 
Hi again, is there any update on this? I can also hop on a call or chat with someone if that helps with the review.

Let me know,

Malte