Date: Thu, 6 Mar 2014 10:41:10 -0700 From: Alan Somers <asomers@freebsd.org> To: Peter Holm <peter@holm.cc> Cc: Garrett Cooper <yanegomi@gmail.com>, "freebsd-testing@freebsd.org" <freebsd-testing@freebsd.org> Subject: Re: Test scenario for sysctl kern.maxfiles Message-ID: <CAOtMX2jGmY9xKUqJH1adrVzNtiR31b8Yvy35B9-2CK42c__1SQ@mail.gmail.com> In-Reply-To: <20140306162934.GB25614@x2.osted.lan> References: <20140305085806.GA70478@x2.osted.lan> <CAOtMX2hUJ2Hc62bG1jitbQbiHtb8b8Jm8iWaP4VaJPuADXR=Kw@mail.gmail.com> <20140306112322.GA10664@x2.osted.lan> <CAF6rxgmDWg3G9td3sXFTouwG_nxc2cP8SjEy81gr1e_Md-HeGA@mail.gmail.com> <20140306153247.GA22830@x2.osted.lan> <6A23D2B5-4EAA-46EF-A582-8C55FE0ED46B@gmail.com> <20140306162934.GB25614@x2.osted.lan>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, Mar 6, 2014 at 9:29 AM, Peter Holm <peter@holm.cc> wrote: > On Thu, Mar 06, 2014 at 07:44:58AM -0800, Garrett Cooper wrote: >> On Mar 6, 2014, at 7:32 AM, Peter Holm <peter@holm.cc> wrote: >> >> > On Thu, Mar 06, 2014 at 09:15:58AM -0500, Eitan Adler wrote: >> >> On 6 March 2014 06:23, Peter Holm <peter@holm.cc> wrote: >> >>> On Wed, Mar 05, 2014 at 10:08:49AM -0700, Alan Somers wrote: >> >>>> On Wed, Mar 5, 2014 at 1:58 AM, Peter Holm <peter@holm.cc> wrote: >> >>>>> Here's an attempt to verify that increasing kern.maxfiles works as >> >>>>> expected. >> >>>>> >> >>>>> http://people.freebsd.org/~pho/kern_descrip_test-v3.diff >> >>>>> -- >> >>>>> Peter >> >>>> >> >>>> 1) done should be of type "static volatile sig_atomic_t", not int, >> >>>> because it's set by signal handlers. >> >>>> >> >>> >> >>> Yes, that is nicer (I learned something new today :-). But the use >> >>> here works because there is a call to usleep(3) after each test, >> >>> forcing the compiler to reload the "done" variable. >> >> >> >> That isn't what sig_atomic_t is trying to prevent. It is an ""integer >> >> type of an object that can be accessed as an atomic entity, even in >> >> the presence of asynchronous interrupts."". In particular, on some >> >> machines it would be possible for the signal handler to observe a >> >> half-updated "int" type variable. >> >> >> >> On i386 sig_atomic_t happens to be an "int". On amd64 it happens to >> >> be a long. This is not contractual. >> >> >> > >> > I only just realize that the ATF test programs are threaded. >> > Anyway it seems to be a good practice to always use "static volatile >> > sig_atomic_t" for signal handler variables. >> >> ATF forks, doesn?t spawns threads: >> >> # grep -r pthread contrib/atf/ || echo not threaded >> not threaded >> > > Hmm ... OK. > > $ ldd /usr/tests/sys/kern/unix_seqpacket_test > /usr/tests/sys/kern/unix_seqpacket_test: > libthr.so.3 => /lib/libthr.so.3 (0x2806f000) > libatf-c.so.1 => /usr/lib/libatf-c.so.1 (0x28091000) > libc.so.7 => /lib/libc.so.7 (0x280a5000) > $ That's my fault. Some of the test cases themselves require threads; not the ATF framework. I could've used fork() for those test cases, but in this case using threads was easier so they could share address space. > >> I think that the point that others were trying to make here is that it sets a good standard/precedence to program with atomicity in mind instead of it not being involved, because of how signal handlers are designed. >> > > Oh, I absolutely agree. > -- > Peter > _______________________________________________ > freebsd-testing@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-testing > To unsubscribe, send any mail to "freebsd-testing-unsubscribe@freebsd.org"
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAOtMX2jGmY9xKUqJH1adrVzNtiR31b8Yvy35B9-2CK42c__1SQ>