Date: Mon, 20 Dec 2004 12:04:11 +0100 From: Peter Holm <peter@holm.cc> To: John Baldwin <jhb@FreeBSD.org> Cc: jroberson@chesapeake.net Subject: Re: Freeze Message-ID: <20041220110411.GA87750@peter.osted.lan> In-Reply-To: <200412161521.44026.jhb@FreeBSD.org> References: <20041112123343.GA12048@peter.osted.lan> <200411191710.19215.jhb@FreeBSD.org> <20041206135934.GA24238@peter.osted.lan> <200412161521.44026.jhb@FreeBSD.org>
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On Thu, Dec 16, 2004 at 03:21:44PM -0500, John Baldwin wrote: > On Monday 06 December 2004 08:59 am, Peter Holm wrote: > > On Fri, Nov 19, 2004 at 05:10:19PM -0500, John Baldwin wrote: > > > On Friday 19 November 2004 02:59 am, Peter Holm wrote: > > > > On Mon, Nov 15, 2004 at 03:46:15PM -0500, John Baldwin wrote: > > > > > On Friday 12 November 2004 07:33 am, Peter Holm wrote: > > > > > > GENERIC HEAD from Nov 11 08:05 UTC > > > > > > > > > > > > The following stack traces etc. was done before my first > > > > > > cup of coffee, so it's not so informative as it could have been :-( > > > > > > > > > > > > The test box appeared to have been frozen for more than 6 hours, > > > > > > but was pingable. > > > > > > > > > > > > http://www.holm.cc/stress/log/cons86.html > > > > > > > > > > A weak guess is that you have the system in some sort of livelock due > > > > > to fork()? Have you tried running with 'debug.mpsafevm=1' set from > > > > > the loader? > > > > > > > > > > -- > > > > > John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ > > > > > "Power Users Use the Power to Serve" = http://www.FreeBSD.org > > > > > > > > OK, I've got some more info: > > > > > > > > http://www.holm.cc/stress/log/cons88.html > > > > > > > > Looks like a spin in uma_zone_slab() when slab_zalloc() fails? > > > > > > Yes, I think if you specify M_WAITOK, then that might happen. > > > slab_zalloc() can fail if any of the init functions fail for example, in > > > which case it would loop forever. You can try this hack (though it may > > > very well be wrong) to return failure if that is what is triggering: > > > > > > Index: uma_core.c > > > =================================================================== > > > RCS file: /usr/cvs/src/sys/vm/uma_core.c,v > > > retrieving revision 1.110 > > > diff -u -r1.110 uma_core.c > > > --- uma_core.c 6 Nov 2004 11:43:30 -0000 1.110 > > > +++ uma_core.c 19 Nov 2004 22:08:26 -0000 > > > @@ -1998,6 +1998,10 @@ > > > */ > > > if (flags & M_NOWAIT) > > > flags |= M_NOVM; > > > + > > > + /* XXXHACK */ > > > + if (flags & M_WAITOK) > > > + break; > > > } > > > return (slab); > > > } > > > > > > -- > > > John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ > > > "Power Users Use the Power to Serve" = http://www.FreeBSD.org > > > > I instrumented the code with this: > > $ cvs diff -u > > cvs diff: Diffing . > > Index: uma_core.c > > =================================================================== > > RCS file: /home/ncvs/src/sys/vm/uma_core.c,v > > retrieving revision 1.110 > > diff -u -r1.110 uma_core.c > > --- uma_core.c 6 Nov 2004 11:43:30 -0000 1.110 > > +++ uma_core.c 6 Dec 2004 13:49:36 -0000 > > @@ -1926,6 +1926,7 @@ > > { > > uma_slab_t slab; > > uma_keg_t keg; > > + int i; > > > > keg = zone->uz_keg; > > > > @@ -1943,7 +1944,8 @@ > > > > slab = NULL; > > > > - for (;;) { > > + for (i = 0;;i++) { > > + KASSERT(i < 10000, ("uma_zone_slab is looping")); > > /* > > * Find a slab with some space. Prefer slabs that are > > partially * used over those that are totally full. This helps to reduce > > > > and now during test of Jeff Roberson's "SMP FFS" patch the assert > > triggered: http://www.holm.cc/stress/log/cons92.html > > Hmm. Does the hack patch above make the hang go away or does it just break > things worse? > I have been testing your patch for quite a while. If it's OK for m_getcl with M_TRYWAIT to return NULL, your patch reviled a missing test for NULL in kern/uipc_socket.c:750 Fatal trap 12: page fault while in kernel mode cpuid = 0; apic id = 00 fault virtual address = 0x1c fault code = supervisor write, page not present instruction pointer = 0x8:0xc0647d77 stack pointer = 0x10:0xcfa9cbf0 frame pointer = 0x10:0xcfa9cc38 code segment = base 0x0, limit 0xfffff, type 0x1b = DPL 0, pres 1, def32 1, gran 1 processor eflags = interrupt enabled, resume, IOPL = 0 current process = 67417 (net) [thread pid 67417 tid 100890 ] Stopped at sosend+0x227: movl $0,0x1c(%eax) db> where Tracing pid 67417 tid 100890 td 0xc1ae8000 sosend(c3454dec,0,cfa9cc90,0,0) at sosend+0x227 soo_write(c1db9374,cfa9cc90,c1aa6180,0,c1ae8000) at soo_write+0x2d dofilewrite(3,bfbfe740,400,ffffffff,ffffffff) at dofilewrite+0x99 write(c1ae8000,cfa9cd14,3,d,246) at write+0x48 syscall(2f,bfbf002f,bfbf002f,3,bfbfe740) at syscall+0x128 Xint0x80_syscall() at Xint0x80_syscall+0x1f --- syscall (4, FreeBSD ELF32, write), eip = 0x280bfbf7, esp = 0xbfbfe71c, ebp = 0xbfbfeb68 --- -- Peter Holm
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