Date: Fri, 4 Oct 2002 15:41:41 +0200 From: Stefan Farfeleder <e0026813@stud3.tuwien.ac.at> To: Poul-Henning Kamp <phk@critter.freebsd.dk> Cc: current@FreeBSD.ORG Subject: Re: Junior Kernel Hacker page updated... Message-ID: <20021004134141.GA263@frog.fafoe> In-Reply-To: <4860.1033656106@critter.freebsd.dk> References: <20021002214028.GA94673@frog.fafoe> <4860.1033656106@critter.freebsd.dk>
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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
%%%
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
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Content-Disposition: attachment; filename="make-cond.diff"
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 */
/*-
--NMuMz9nt05w80d4+--
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