Date: Fri, 4 Oct 2002 13:22:03 -0700 From: Juli Mallett <jmallett@FreeBSD.org> To: Stefan Farfeleder <e0026813@stud3.tuwien.ac.at> Cc: Poul-Henning Kamp <phk@critter.freebsd.dk>, current@FreeBSD.ORG Subject: Re: Junior Kernel Hacker page updated... Message-ID: <20021004132203.A78223@FreeBSD.org> In-Reply-To: <20021004134141.GA263@frog.fafoe>; from e0026813@stud3.tuwien.ac.at on Fri, Oct 04, 2002 at 03:41:41PM %2B0200 References: <20021002214028.GA94673@frog.fafoe> <4860.1033656106@critter.freebsd.dk> <20021004134141.GA263@frog.fafoe>
next in thread | previous in thread | raw e-mail | index | archive | help
* De: Stefan Farfeleder <e0026813@stud3.tuwien.ac.at> [ Data: 2002-10-04 ]
[ Subjecte: Re: Junior Kernel Hacker page updated... ]
> On Thu, Oct 03, 2002 at 04:41:46PM +0200, Poul-Henning Kamp wrote:
> >
> > Hi Stefan,
> >
> > I tried this patch and it paniced my (almost-) current machine with
> > a pagefault in the kqueue code: Bravo!
> >
> > I can see that there is some amount of #ifdef stuff in your patch,
>
> The #ifdefs are already in the code, namely REMOTE and RMT_WILL_WATCH.
> Is anybody using them? Building with -DREMOTE doesn't compile and with
> -DRMT_WILL_WATCH the linker is complaining about the lack of the
> functions Rmt_Ignore(), Rmt_Watch() and Rmt_Wait(). Can't we get rid of
> those defines? I understand Juli Mallett wants to rewrite make, so maybe
> this effort would be wasted.
>
> > in light of that, would it be possible to make an #ifdef'ed version
> > of your patch which we could commit ?
>
> Ok, the new patch is attached. Compile with -DUSE_KQUEUE to use the new
> code.
>
> > That way we give the kqueue hackers a good testcase, and we can
> > easily enable when they have solved the problem.
>
> After Don Lewis fixed the 'could sleep with' problem (thanks!), I'm
> still encountering freezes and panics. Here's one I caught:
>
> [warning: parts are typed in]
> %%%
> Fatal trap 12: page fault while in kernel mode
> cpuid = 0; lapic.id = 00000000
> fault virtual address = 0x8
> fault code = supervisor read, page not present
> instruction pointer = 0x8:0xc01a1212
> stack pointer = 0x10:0xe5226c14
> frame pointer = 0x10:0xe5226ca0
> 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 = 56525 (make)
>
> kernel: type 12 trap, code = 0
>
> Stopped at kqueue_scan+0x242: cmpl $0,0x8(%ebx)
> db> trace
> kqueue_scan(c6472bf4,4,bfbfebc0,0,c70ecea0) at kqueue_scan+0x242
> kevent(c70ecea0,e5226d10,c0351d80,418,6) at kevent+0x1e1
> syscall(2f,2f,2f,818d780,818d960) at syscall+0x2be
> %%%
Run the kqueue source file through gcc with -fverbose-asm -S and then
look at the resulting .s file, grep for cmpl.*0x8( and look for
what's being dereferenced without being checked for NULL.
> The core file doesn't seem to be particularly helpful, as the
> kqueue_scan frame seems to miss:
>
> %%%
> (kgdb) bt
> #0 doadump () at /freebsd/current/src/sys/kern/kern_shutdown.c:223
> #1 0xc01ba92a in boot (howto=260)
> at /freebsd/current/src/sys/kern/kern_shutdown.c:355
> #2 0xc01babe7 in panic () at /freebsd/current/src/sys/kern/kern_shutdown.c:508
> #3 0xc013b1d2 in db_panic () at /freebsd/current/src/sys/ddb/db_command.c:450
> #4 0xc013b152 in db_command (last_cmdp=0xc035db20, cmd_table=0x0,
> aux_cmd_tablep=0xc03577dc, aux_cmd_tablep_end=0xc03577e0)
> at /freebsd/current/src/sys/ddb/db_command.c:346
> #5 0xc013b266 in db_command_loop ()
> at /freebsd/current/src/sys/ddb/db_command.c:472
> #6 0xc013deca in db_trap (type=12, code=0)
> at /freebsd/current/src/sys/ddb/db_trap.c:72
> #7 0xc02e9f60 in kdb_trap (type=12, code=0, regs=0xe5226bd4)
> at /freebsd/current/src/sys/i386/i386/db_interface.c:166
> #8 0xc0302602 in trap_fatal (frame=0xe5226bd4, eva=0)
> at /freebsd/current/src/sys/i386/i386/trap.c:841
> #9 0xc03022e2 in trap_pfault (frame=0xe5226bd4, usermode=0, eva=8)
> at /freebsd/current/src/sys/i386/i386/trap.c:760
> #10 0xc0301e0d in trap (frame=
> {tf_fs = 24, tf_es = 16, tf_ds = 16, tf_edi = -943606528, tf_esi = -943606488, tf_ebp = -450728800, tf_isp = -450728960, tf_ebx = 0, tf_edx = 4, tf_ecx = 1, tf_eax = 0, tf_trapno = 12, tf_err = 0, tf_eip = -1072033262, tf_cs = 8, tf_eflags = 66050, tf_esp = -966356416, tf_ss = 0})
> ---Type <return> to continue, or q <return> to quit---
> at /freebsd/current/src/sys/i386/i386/trap.c:446
> #11 0xc02eb768 in calltrap () at {standard input}:99
> #12 0xc01a0ad1 in kevent (td=0xc70ecea0, uap=0xe5226d10)
> at /freebsd/current/src/sys/kern/kern_event.c:470
> #13 0xc030299e in syscall (frame=
> {tf_fs = 47, tf_es = 47, tf_ds = 47, tf_edi = 135845760, tf_esi = 135846240, tf_ebp = -1077941224, tf_isp = -450728588, tf_ebx = 134831872, tf_edx = 2184, tf_ecx = 0, tf_eax = 363, tf_trapno = 12, tf_err = 2, tf_eip = 134626551, tf_cs = 31, tf_eflags = 514, tf_esp = -1077941348, tf_ss = 47})
> at /freebsd/current/src/sys/i386/i386/trap.c:1050
> #14 0xc02eb7bd in Xint0x80_syscall () at {standard input}:141
> ---Can't read userspace from dump, or kernel process---
> %%%
>
> objdump -dS kern_event.o says the following about kqueue_scan+0x242
> [==0xfd2]:
>
> %%%
> fce: 90 nop
> fcf: 90 nop
> kn = TAILQ_FIRST(&kq->kq_head);
> fd0: 8b 1f mov (%edi),%ebx
> TAILQ_REMOVE(&kq->kq_head, kn, kn_tqe);
> fd2: 83 7b 08 00 cmpl $0x0,0x8(%ebx)
> fd6: 74 0b je fe3 <kqueue_scan+0x253>
> fd8: 8b 53 08 mov 0x8(%ebx),%edx
> fdb: 8b 43 0c mov 0xc(%ebx),%eax
> fde: 89 42 0c mov %eax,0xc(%edx)
> fe1: eb 06 jmp fe9 <kqueue_scan+0x259>
> fe3: 8b 43 0c mov 0xc(%ebx),%eax
> fe6: 89 47 04 mov %eax,0x4(%edi)
> fe9: 8b 43 0c mov 0xc(%ebx),%eax
> fec: 8b 53 08 mov 0x8(%ebx),%edx
> fef: 89 10 mov %edx,(%eax)
> if (kn == &marker) {
> ff1: 8d 45 b4 lea 0xffffffb4(%ebp),%eax
> ff4: 39 c3 cmp %eax,%ebx
> ff6: 75 18 jne 1010 <kqueue_scan+0x280>
> splx(s);
> [...]
> %%%
>
> This seems to indicate that TAILQ_FIRST returns a null pointer and
> TAILQ_REMOVE tries to dereference it, doesn't it? Maybe 'count' is not 0
> though it should be?
>
> Regards,
> Stefan Farfeleder
> Index: job.c
> ===================================================================
> RCS file: /home/ncvs/src/usr.bin/make/job.c,v
> retrieving revision 1.43
> diff -u -r1.43 job.c
> --- job.c 29 Sep 2002 00:20:28 -0000 1.43
> +++ job.c 4 Oct 2002 10:58:52 -0000
> @@ -106,6 +106,7 @@
> #include <sys/stat.h>
> #include <sys/file.h>
> #include <sys/time.h>
> +#include <sys/event.h>
> #include <sys/wait.h>
> #include <err.h>
> #include <errno.h>
> @@ -237,9 +238,13 @@
> * (2) a job can only be run locally, but
> * nLocal equals maxLocal */
> #ifndef RMT_WILL_WATCH
> +#ifdef USE_KQUEUE
> +static int kqfd; /* File descriptor obtained by kqueue() */
> +#else
> static fd_set outputs; /* Set of descriptors of pipes connected to
> * the output channels of children */
> #endif
> +#endif
>
> STATIC GNode *lastNode; /* The node for which output was most recently
> * produced. */
> @@ -692,7 +697,7 @@
> if (usePipes) {
> #ifdef RMT_WILL_WATCH
> Rmt_Ignore(job->inPipe);
> -#else
> +#elif !defined(USE_KQUEUE)
> FD_CLR(job->inPipe, &outputs);
> #endif
> if (job->outPipe != job->inPipe) {
> @@ -1267,10 +1272,22 @@
> * position in the buffer to the beginning and mark another
> * stream to watch in the outputs mask
> */
> +#ifdef USE_KQUEUE
> + struct kevent kev[2];
> +#endif
> job->curPos = 0;
>
> #ifdef RMT_WILL_WATCH
> Rmt_Watch(job->inPipe, JobLocalInput, job);
> +#elif defined(USE_KQUEUE)
> + EV_SET(&kev[0], job->inPipe, EVFILT_READ, EV_ADD, 0, 0, job);
> + EV_SET(&kev[1], job->pid, EVFILT_PROC, EV_ADD | EV_ONESHOT,
> + NOTE_EXIT, 0, NULL);
> + if (kevent(kqfd, kev, 2, NULL, 0, NULL) != 0) {
> + /* kevent() will fail if the job is already finished */
> + if (errno != EBADF && errno != ESRCH)
> + Punt("kevent: %s", strerror(errno));
> + }
> #else
> FD_SET(job->inPipe, &outputs);
> #endif /* RMT_WILL_WATCH */
> @@ -2229,10 +2246,16 @@
> Job_CatchOutput()
> {
> int nfds;
> +#ifdef USE_KQUEUE
> +#define KEV_SIZE 4
> + struct kevent kev[KEV_SIZE];
> + int i;
> +#else
> struct timeval timeout;
> fd_set readfds;
> LstNode ln;
> Job *job;
> +#endif
> #ifdef RMT_WILL_WATCH
> int pnJobs; /* Previous nJobs */
> #endif
> @@ -2262,6 +2285,27 @@
> }
> #else
> if (usePipes) {
> +#ifdef USE_KQUEUE
> + if ((nfds = kevent(kqfd, NULL, 0, kev, KEV_SIZE, NULL)) == -1) {
> + Punt("kevent: %s", strerror(errno));
> + } else {
> + for (i = 0; i < nfds; i++) {
> + if (kev[i].flags & EV_ERROR) {
> + warnc(kev[i].data, "kevent");
> + continue;
> + }
> + switch (kev[i].filter) {
> + case EVFILT_READ:
> + JobDoOutput(kev[i].udata, FALSE);
> + break;
> + case EVFILT_PROC:
> + /* Just wake up and let Job_CatchChildren() collect the
> + * terminated job. */
> + break;
> + }
> + }
> + }
> +#else
> readfds = outputs;
> timeout.tv_sec = SEL_SEC;
> timeout.tv_usec = SEL_USEC;
> @@ -2282,6 +2326,7 @@
> }
> Lst_Close(jobs);
> }
> +#endif /* !USE_KQUEUE */
> }
> #endif /* RMT_WILL_WATCH */
> }
> @@ -2408,6 +2453,12 @@
> }
> if (signal(SIGWINCH, SIG_IGN) != SIG_IGN) {
> (void) signal(SIGWINCH, JobPassSig);
> + }
> +#endif
> +
> +#ifdef USE_KQUEUE
> + if ((kqfd = kqueue()) == -1) {
> + Punt("kqueue: %s", strerror(errno));
> }
> #endif
>
> Index: job.h
> ===================================================================
> RCS file: /home/ncvs/src/usr.bin/make/job.h,v
> retrieving revision 1.18
> diff -u -r1.18 job.h
> --- job.h 26 Sep 2002 01:39:22 -0000 1.18
> +++ job.h 4 Oct 2002 10:55:11 -0000
> @@ -50,6 +50,7 @@
>
> #define TMPPAT "/tmp/makeXXXXXXXXXX"
>
> +#ifndef USE_KQUEUE
> /*
> * The SEL_ constants determine the maximum amount of time spent in select
> * before coming out to see if a child has finished. SEL_SEC is the number of
> @@ -57,6 +58,7 @@
> */
> #define SEL_SEC 0
> #define SEL_USEC 100000
> +#endif /* !USE_KQUEUE */
>
>
> /*-
--
Juli Mallett <jmallett@FreeBSD.org> | FreeBSD: The Power To Serve
Will break world for fulltime employment. | finger jmallett@FreeBSD.org
http://people.FreeBSD.org/~jmallett/ | Support my FreeBSD hacking!
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20021004132203.A78223>