Re: port-alpha/48782: # top [1] Floating point exception (core dumped) top

["Naruaki.Etomi" <nullnilaki%gmail.com@localhost>]

The following reply was made to PR port-alpha/48782; it has been noted by GNATS.

From: "Naruaki.Etomi" <nullnilaki%gmail.com@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: port-alpha-maintainer%netbsd.org@localhost, martin%duskware.de@localhost
Subject: Re: port-alpha/48782: # top [1] Floating point exception (core
 dumped) top
Date: Sat, 10 May 2014 17:55:11 +0900

 I think that this case is conflict between pcu_load() and fpu_state_load().
 
 ---------------------------
 
 -mieee-with-inexact option use:
 
 /usr/src/sys/arch/alpha/alpha/fp_complete.c
 static int
 alpha_fp_complete_at(alpha_instruction *trigger_pc, struct lwp *l,
     uint64_t *ucode)
 {
         int needsig;
     ...
         if (__predict_false(copyin(trigger_pc, &inst, sizeof inst))) {
                 this_cannot_happen(6, -1);
                 return SIGSEGV;
         }
         fpu_load(); <---------------------------------------------------- point
         alpha_pal_wrfen(1);
 
 
 
 /usr/src/sys/kern/subr_pcu.c
 pcu_load(const pcu_ops_t *pcu)
 {
         const u_int id = pcu->pcu_id;
     ...
 
         /* Does this CPU already have our PCU state loaded? */
         if (ci == curci) {
                 KASSERT(curci->ci_pcu_curlwp[id] == l);
                 KASSERT(pcu_used_p(pcu));
                 panic("Re-enable");  <----------------------------------- point
                 /* Re-enable */
                 pcu->pcu_state_load(l, PCU_LOADED | PCU_ENABLE);
 <------- point
 
 panic: Re-enable
 Stopped in pid 411.1 (a.out) at netbsd:cpu_Debugger+0x4: ret zero,(ra
 )
 db> tr
 cpu_Debugger() at netbsd:cpu_Debugger+0x4
 db_panic() at netbsd:db_panic+0x118
 vpanic() at netbsd:vpanic+0x1a8
 panic() at netbsd:panic+0x58
 pcu_load() at netbsd:pcu_load+0x288
 alpha_fp_complete_at() at netbsd:alpha_fp_complete_at+0x60
 alpha_fp_complete() at netbsd:alpha_fp_complete+0x78
 trap() at netbsd:trap+0x114
 XentArith() at netbsd:XentArith+0x20
 --- arithmetic trap (from ipl 0) ---
 --- user mode ---
 
 ---------------------------
 
 I think that trapb instruction incompatible with fpu_state_load().
 
 ---------------------------
 
 # diff -u fp_complete.c.orig fp_complete.c
 --- fp_complete.c.orig 2014-05-10 08:02:31.000000000 +0000
 +++ fp_complete.c 2014-05-10 07:48:32.000000000 +0000
 @@ -721,6 +721,10 @@
 void
 fpu_state_load(struct lwp *l, u_int flags)
 {
 + if ((PCU_LOADED | PCU_ENABLE) == flags) {
 + return;
 + }
 +
 struct pcb * const pcb = lwp_getpcb(l);
 
 ---------------------------
 
 Is it right?
 Please review.
 
 ---------------------------
 
  PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND
 0 root 96 0 0K 13M atath 0:01 0.00% 0.00% [system]
 466 root 43 0 3992K 2240K CPU 0:00 0.00% 0.00% top
 404 root 85 0 9840K 4088K wait 0:00 0.00% 0.00% login
 158 root 85 0 7536K 2592K kqueue 0:00 0.00% 0.00% syslogd
 396 root 85 0 3888K 2280K wait 0:00 0.00% 0.00% sh
 325 root 85 0 3776K 1736K kqueue 0:00 0.00% 0.00% inetd
 1 root 85 0 3624K 1704K wait 0:00 0.00% 0.00% init
 397 root 85 0 3568K 1536K nanoslp 0:00 0.00% 0.00% cron
 412 root 43 0 32M 18M parked 0:00 0.00% 0.00% dhclient
 
 # vi test.c
 
 #include <stdio.h>
 
 int main (int argc, char *argv[])
 {
 double a, b, c;
 
 a = 1.;
 b = 3.;
 c = a/b;
 
 fprintf (stderr, "%g / %g = %g\n", a, b, c);
 }
 
 # gcc -mieee-with-inexact test.c
 # ./a.out
 1 / 3 = 0.333333
 
 ---------------------------
 
 ---
 That's very nice of you!
 Naruaki Etomi / nullnilaki%gmail.com@localhost