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| Message-ID: | <544A327E.9090006@dronecode.org.uk> |
| Date: | Fri, 24 Oct 2014 12:05:34 +0100 |
| From: | Jon TURNEY <jon DOT turney AT dronecode DOT org DOT uk> |
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| To: | cygwin AT cygwin DOT com |
| Subject: | Re: Threads |
| References: | <54450835 DOT 3050602 AT cornell DOT edu> <5448E6F9 DOT 8040005 AT dronecode DOT org DOT uk> <5448EEBF DOT 3020706 AT cornell DOT edu> <20141023153730 DOT GC20607 AT calimero DOT vinschen DOT de> |
| In-Reply-To: | <20141023153730.GC20607@calimero.vinschen.de> |
--------------050205010203090604010408 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit On 23/10/2014 16:37, Corinna Vinschen wrote: > On Oct 23 08:04, Ken Brown wrote: >> On 10/23/2014 7:31 AM, Jon TURNEY wrote: >>> On 20/10/2014 14:03, Ken Brown wrote: >>>> Or is there some other plausible explanation for "impossible" crashes? >>>> This can't just be a result of a gdb bug, because in at least one case >>>> the assertion can be shown to be valid by using printf instead of gdb. >>>> >>>> [*] By "impossible" I mean that examination of the relevant variables in >>>> gdb shows that the assertions are in fact true. Two ongoing examples are >>>> >>>> http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18438 >>>> http://debbugs.gnu.org/cgi/bugreport.cgi?bug=18769 >>> >>> As a suggestion, you might want to also take a careful look at how signal >>> delivery is implemented in cygwin on x86_64 >>> >>> I had a vague idea that there was, at some time in the past, a fix made for >>> register corruption on x86_64 after a signal was handled, but I can't find it >>> now, so maybe I imagined it. >> >> Is this what you're thinking of? >> >> https://cygwin.com/ml/cygwin-cvs/2014-q1/msg00020.html >> >>> But if for e.g. the flags register was getting >>> corrupted when a signal interrupts the main thread, that could perhaps also >>> explain what is being seen. >> >> Yes, flags register corruption is exactly what Eli suggested in the other >> bug report I cited. > > The aforementioned patch was supposed to fix this problem and it is > definitely in the current 1.7.32 release... I didn't mean to suggest otherwise, just that perhaps a similar problem exists now. So I made the attached test case to explore that. Maybe I've made an obvious mistake with it, but on the face of it, it seems to demonstrate something... jon AT tambora / $ gcc signal-stress.c -Wall -O0 -g jon AT tambora / $ ./a failed: 2144210386 isn't equal to 2144210386, apparently Note there is some odd load dependency. For me, it works fine when it's the only thing running, but when I start up something CPU intensive, it often fails... --------------050205010203090604010408 Content-Type: text/plain; charset=windows-1252; name="signal-stress.c" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="signal-stress.c" CiNpbmNsdWRlIDxhc3NlcnQuaD4KI2luY2x1ZGUgPHN5cy90aW1lLmg+CiNp bmNsdWRlIDxzaWduYWwuaD4KI2luY2x1ZGUgPHN0ZGlvLmg+Cgpsb25nIFNt YXJ0U2NoZWR1bGVJbnRlcnZhbCA9IDE7IC8qIG1zICovCmxvbmcgU21hcnRT Y2hlZHVsZVRpbWUgPSAwOwoKc3RhdGljIHZvaWQKU21hcnRTY2hlZHVsZVRp bWVyKGludCBzaWcpCnsKICAgIGlmIChzaWcgIT0gMCkKICAgICAgIFNtYXJ0 U2NoZWR1bGVUaW1lICs9IFNtYXJ0U2NoZWR1bGVJbnRlcnZhbDsKfQoKdm9p ZApTbWFydFNjaGVkdWxlU3RhcnRUaW1lcih2b2lkKQp7CiAgICBzdHJ1Y3Qg aXRpbWVydmFsIHRpbWVyOwogICAgdGltZXIuaXRfaW50ZXJ2YWwudHZfc2Vj ID0gMDsKICAgIHRpbWVyLml0X2ludGVydmFsLnR2X3VzZWMgPSBTbWFydFNj aGVkdWxlSW50ZXJ2YWwgKiAxMDAwOwogICAgdGltZXIuaXRfdmFsdWUudHZf c2VjID0gMDsKICAgIHRpbWVyLml0X3ZhbHVlLnR2X3VzZWMgPSBTbWFydFNj aGVkdWxlSW50ZXJ2YWwgKiAxMDAwOwogICAgc2V0aXRpbWVyKElUSU1FUl9S RUFMLCAmdGltZXIsIDApOwp9CgppbnQgbWFpbigpCnsKICAgIC8qIFNldCB1 cCB0aGUgdGltZXIgc2lnbmFsIGZ1bmN0aW9uICovCiAgICBzdHJ1Y3Qgc2ln YWN0aW9uIGFjdDsKICAgIGFjdC5zYV9oYW5kbGVyID0gU21hcnRTY2hlZHVs ZVRpbWVyOwogICAgc2lnZW1wdHlzZXQoJmFjdC5zYV9tYXNrKTsKICAgIHNp Z2FkZHNldCgmYWN0LnNhX21hc2ssIFNJR0FMUk0pOwogICAgaWYgKHNpZ2Fj dGlvbihTSUdBTFJNLCAmYWN0LCAwKSA8IDApIHsKICAgICAgICBwZXJyb3Io InNpZ2FjdGlvbiBmYWlsZWQiKTsKCXJldHVybiAtMTsKICAgIH0KCiAgIC8q IHN0YXJ0IHRpbWVyICovCiAgIFNtYXJ0U2NoZWR1bGVTdGFydFRpbWVyKCk7 CgogICAvKiBMb29wIGZvcmV2ZXIsIGRvaW5nIHRlc3RzIHdoaWNoIHNob3Vs ZCBhbHdheXMgc3VjY2VlZCwgd2l0aCBsb3RzIG9mIHNpZ25hbHMgKi8KICAg aW50IHggPSAwOwogICBpbnQgaSA9IDA7CiAgIHdoaWxlICgxKSB7CiAgICAg eCA9IGk7CiAgICAgaW50IGogPSB4OwogICAgIGlmIChqICE9IGkpCiAgICAg ICB7CiAgICAgICAgICBwcmludGYoImZhaWxlZDogJWQgaXNuJ3QgZXF1YWwg dG8gJWQsIGFwcGFyZW50bHlcbiIsIGksIGopOwogICAgICAgICAgYnJlYWs7 CiAgICAgICB9CiAgICAgaSsrOwogIH0KICByZXR1cm4gMDsKfQo= --------------050205010203090604010408 Content-Type: text/plain; charset=us-ascii -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple --------------050205010203090604010408--
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