Bug#855118: wrk: only loops and burns CPU

[Robert Edmonds]

Christos Trochalakis wrote:
> I plan to upload it as an nmu on Monday unless Robert wants to prepare
> the upload himself. I have just pushed those fixes to the packaging repo
> (nmu branch).
> 
> https://anonscm.debian.org/cgit/collab-maint/wrk.git/log/?h=nmu

Thanks, just uploaded these changes as 4.0.2-2.

-- 
Robert Edmonds
edmo...@debian.org

Bug#855118: wrk: only loops and burns CPU

[Christos Trochalakis]

On Tue, Aug 01, 2017 at 02:10:18AM +0300, Rinat Ibragimov wrote:

Hi.

Looks like patch intended to fix FTBFS was wrong. And rendered wrk unusable.

One can't just replace __sync_val_compare_and_swap by
__atomic_compare_exchange without other changes, since former function returns
previous value of the atomic variable, while latter returns a boolean value. 
True for
success. Placing that value into "max" starts a infinite loop if n was larger 
than 1,
which is almost always.

Proposed patch attached.



I have also confirmed that the above patch fixes the busy-loop issue. I
have prepared an upload that fixes this bug by including your patch and
correctly handles the mips FTBFS (#801881).

I plan to upload it as an nmu on Monday unless Robert wants to prepare
the upload himself. I have just pushed those fixes to the packaging repo
(nmu branch).

https://anonscm.debian.org/cgit/collab-maint/wrk.git/log/?h=nmu

Bug#855118: wrk: only loops and burns CPU

[Rinat Ibragimov]

Hi.

Looks like patch intended to fix FTBFS was wrong. And rendered wrk unusable.

One can't just replace __sync_val_compare_and_swap by
__atomic_compare_exchange without other changes, since former function returns
previous value of the atomic variable, while latter returns a boolean value. 
True for
success. Placing that value into "max" starts a infinite loop if n was larger 
than 1,
which is almost always.

Proposed patch attached.

---
Rinatdiff -urN wrk-4.0.2-prev/src/stats.c wrk-4.0.2/src/stats.c
--- wrk-4.0.2-prev/src/stats.c	2017-08-01 01:35:38.0 +0300
+++ wrk-4.0.2/src/stats.c	2017-08-01 01:57:00.900436161 +0300
@@ -25,8 +25,17 @@
 __atomic_fetch_add(>count, 1, __ATOMIC_SEQ_CST);
 uint64_t min = stats->min;
 uint64_t max = stats->max;
-while (n < min) min = __atomic_compare_exchange(>min, , , false,__ATOMIC_SEQ_CST,__ATOMIC_SEQ_CST);
-while (n > max) max = __atomic_compare_exchange(>max, , , false,__ATOMIC_SEQ_CST,__ATOMIC_SEQ_CST);
+while (n < min) {
+__atomic_compare_exchange(>min, , , false,
+  __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
+min = stats->min;
+}
+while (n > max) {
+__atomic_compare_exchange(>max, , , false,
+  __ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST);
+max = stats->max;
+}
+
 return 1;
 }
 

Bug#855118: wrk: only loops and burns CPU

[Philipp Marek]

Package: wrk
Version: 4.0.2-1+b1
Severity: normal

This version of "wrk" is broken.
Running it eg. via 

# wrk  http://127.0.0.1:3309/static

just makes it loop and burn some CPU; it never terminates, and doesn't even 
do many HTTP requests.

Version 4.0.1-2 (from yakkety) works as expected.


-- System Information:
Debian Release: 9.0
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'unstable'), (500, 'stable'), (1, 
'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 4.9.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=de_AT.UTF-8, LC_CTYPE=de_AT.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages wrk depends on:
ii  libc62.24-9
ii  libluajit-5.1-2  2.0.4+dfsg-1
ii  libssl1.11.1.0d-2

wrk recommends no packages.

wrk suggests no packages.

-- no debconf information