Date: Thu, 15 Nov 2001 14:56:31 -0500 (EST) From: Joe Clarke <marcus@marcuscom.com> To: Maxim Sobolev <sobomax@FreeBSD.org> Cc: freebsd-ports@FreeBSD.org, <freebsd-stable@FreeBSD.org>, <hackers@FreeBSD.org> Subject: Re: sigreturn: eflags creash (fixed!) Message-ID: <20011115145029.G47613-200000@shumai.marcuscom.com> In-Reply-To: <3BF41BE2.BD7D8EAA@FreeBSD.org>
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This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. Send mail to mime@docserver.cac.washington.edu for more info. --0-2136882512-1005854191=:47613 Content-Type: TEXT/PLAIN; charset=US-ASCII On Thu, 15 Nov 2001, Maxim Sobolev wrote: > Joe Clarke wrote: > > > > Sorry for the wide distribution, but I have sent email to both lists > > regarding this problem in the past. It seems that while doing intensive > > threaded operations in Gnome applications, crashes occur with the > > following kernel message: > > > > sigreturn: eflags 0x280 > > > > And, in .gnomerc-errors: > > > > Fatal error 'Thread has returned from sigreturn or longjump' > > > > The problem as I have found it is with libpng. libpng uses MMX > > optimizations by default on FreeBSD. If you apply the attached patch to > > patch-aa in /usr/ports/graphics/png, the problem goes away. You only need > > to recompile and install libpng. Reinstalling Gnome isn't necessary. It > > seems the MMX optimizations are corrupting eflags, and when a thread tries > > to restore context after a signal, things go really wrong. > > > > The true fix will probably come in analyzing the MMX code in libpng. > > Unfortunately, I don't know enough about x86 assembly to be of much use > > here. Hopefully this will help other experiencing the same problem. > > Very interesting, and weird if true. I'll test this tomorrow. In the > meantime, could some CPU guru confirm or reject theoretical > possibility of MMX user-level code causing problems to the kernel? I learned about this by reading through some of the -hackers archives. One person complained of similar errors trying to get xine to work on FreeBSD. Removing the MMX detection code fixed it. I remembered libpng also used MMX, so I removed the pnggccrd.c source, and voila! Based on core dumps, strace output, and a lot of code surfing, this makes sense to me. Basically, any png-dependent app's thread that runs longer than what ITIMER_PROF is set to gets hit with a SIGPROF. When that happens, things context switch. eflags must have been corrupted by the MMX code, thus sigreturn() bombs out, and causes uthread_kern to die as well. Here's what strace looks like when balsa tries to read a 33 MB mailbox: ... 74202 --- SIGPROF (Profiling timer expired) --- 74202 --- SIGPROF (Profiling timer expired) --- 74202 gettimeofday({1005789324, 257513}, NULL) = 0 74202 sigprocmask(SIG_SETMASK, [], NULL) = 0 74202 sigaltstack({ss_sp=0x811b000, ss_flags=0, ss_size=40960}, NULL) = 0 74202 poll([{fd=5, events=POLLIN}, {fd=7, events=POLLIN}, {fd=10, events=POLLIN}, {fd=11, events=POLLIN|POLLPRI}, {fd=13, events=POLLIN}, {fd=12, events=POLLIN}], 6, 0) = 0 74202 sigreturn(0x81f2c64 When this happens, strace politely dies with a bus error. Thanks for testing this, Maxim. Hopefully someone can find the problem and fix it for good. Joe P.S. my original patch sucks I was in a hurry. The one attached is better. > > -Maxim > > --0-2136882512-1005854191=:47613 Content-Type: TEXT/PLAIN; charset=US-ASCII; name="patch-aa.diff" Content-Transfer-Encoding: BASE64 Content-ID: <20011115145631.X47613@shumai.marcuscom.com> Content-Description: Content-Disposition: attachment; filename="patch-aa.diff" LS0tIHBhdGNoLWFhLm9yaWcJVGh1IE5vdiAxNSAxNDo1NTo0MyAyMDAxDQor KysgcGF0Y2gtYWEJVGh1IE5vdiAxNSAxNDo1NTo1NyAyMDAxDQpAQCAtNDMs OCArNDMsOCBAQA0KICANCiAtYWxsOiBsaWJwbmcuYSBwbmd0ZXN0DQogKy5p ZiAoJHtBUkNIfSA9PSAiaTM4NiIpDQotK0NGTEFHUys9LURQTkdfVVNFX1BO R0dDQ1JEDQotK09CSlMrPXBuZ2djY3JkLm8NCisrI0NGTEFHUys9LURQTkdf VVNFX1BOR0dDQ1JEDQorKyNPQkpTKz1wbmdnY2NyZC5vDQogKy5lbmRpZg0K ICsNCiArLlNVRkZJWEVTOiAuYyAuc28gLm8NCkBAIC05MSw1ICs5MSw1IEBA DQogIHBuZ3d0cmFuLm86IHBuZy5oIHBuZ2NvbmYuaA0KICBwbmd3dXRpbC5v OiBwbmcuaCBwbmdjb25mLmgNCiAgcG5ncHJlYWQubzogcG5nLmggcG5nY29u Zi5oDQotK3BuZ2djY3JkLm86IHBuZy5oIHBuZ2NvbmYuaCBwbmdhc21yZC5o DQorKyNwbmdnY2NyZC5vOiBwbmcuaCBwbmdjb25mLmggcG5nYXNtcmQuaA0K ICANCg== --0-2136882512-1005854191=:47613-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-ports" in the body of the message
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