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-rw-r--r--open_issues/fork_mach_port_mod_refs_ekern_urefs_owerflow.mdwn161
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+[[!meta copyright="Copyright © 2010 Free Software Foundation, Inc."]]
+
+[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
+id="license" text="Permission is granted to copy, distribute and/or modify this
+document under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
+
+[[!meta title="fork: mach_port_mod_refs: EKERN_UREFS_OWERFLOW"]]
+
+In the [[GCC testsuite|gcc/testsuite]], at this point:
+
+ Running /home/tschwinge/tmp/gcc/hurd/gcc/testsuite/gcc.c-torture/unsorted/unsorted.exp ...
+
+... `expect` had gone bonkers:
+
+ $ ps --all --format=hurd-long -w
+ PID UID PPID PGrp Sess TH Vmem RSS %CPU User System Args
+ [...]
+ 3567 1000 10295 3567 3567 2 137M 856K 98.2 5hrs 28 hours expect -- /usr/share/dejagnu/runtest.exp --tool gcc
+ [...]
+
+Last lines of `gcc/testsuite/gcc/gcc.sum`:
+
+ PASS: gcc.c-torture/unsorted/q.c, -O2 -flto -flto-partition=none
+ PASS: gcc.c-torture/unsorted/q.c, -O2 -flto
+ PASS: gcc.c-torture/unsorted/r.c, -O0
+ PASS: gcc.c-torture/unsorted/r.c, -O1
+ PASS: gcc.c-torture/unsorted/r.c, -O2
+ PASS: gcc.c-torture/unsorted/r.c, -O3 -fomit-frame-pointer
+ PASS: gcc.c-torture/unsorted/r.c, -O3 -g
+ PASS: gcc.c-torture/unsorted/r.c, -Os
+ PASS: gcc.c-torture/unsorted/r.c, -O2 -flto -flto-partition=none
+
+Last lines of `gcc/testsuite/gcc/gcc.log`:
+
+ Executing on host: /media/data/home/tschwinge/tmp/gcc/hurd.build/gcc/xgcc -B/media/data/home/tschwinge/tmp/gcc/hurd.build/gcc/ -w -O2 -flto -flto-partition=none -c -o /home/tschwinge/tmp/gcc/hurd.build/gcc/testsuite/gcc/r.o /home/tschwinge/tmp/gcc/hurd/gcc/testsuite/gcc.c-torture/unsorted/r.c (timeout = 300)
+ spawn /media/data/home/tschwinge/tmp/gcc/hurd.build/gcc/xgcc -B/media/data/home/tschwinge/tmp/gcc/hurd.build/gcc/ -w -O2 -flto -flto-partition=none -c -o /home/tschwinge/tmp/gcc/hurd.build/gcc/testsuite/gcc/r.o /home/tschwinge/tmp/gcc/hurd/gcc/testsuite/gcc.c-torture/unsorted/r.c
+ PASS: gcc.c-torture/unsorted/r.c, -O2 -flto -flto-partition=none
+ Executing on host: /media/data/home/tschwinge/tmp/gcc/hurd.build/gcc/xgcc -B/media/data/home/tschwinge/tmp/gcc/hurd.build/gcc/ -w -O2 -flto -c -o /home/tschwinge/tmp/gcc/hurd.build/gcc/testsuite/gcc/r.o /home/tschwinge/tmp/gcc/hurd/gcc/testsuite/gcc.c-torture/unsorted/r.c (timeout = 300)
+ spawn /media/data/home/tschwinge/tmp/gcc/hurd.build/gcc/xgcc -B/media/data/home/tschwinge/tmp/gcc/hurd.build/gcc/ -w -O2 -flto -c -o /home/tschwinge/tmp/gcc/hurd.build/gcc/testsuite/gcc/r.o /home/tschwinge/tmp/gcc/hurd/gcc/testsuite/gcc.c-torture/unsorted/r.c
+
+The root filesystem is sort-of deadlocked: `syncfs -c /` doesn't finish
+-- even without `-s`. But it is fine to spawn new processes, execute new
+commands, etc.
+
+GDB on 3567:
+
+ (gdb) info threads
+ 2 Thread 3567.2 0x011aaf4c in mach_msg_trap () at /build/buildd-eglibc_2.11.2-7-hurd-i386-6JVoJz/eglibc-2.11.2/build-tree/hurd-i386-libc/mach/mach_msg_trap.S:2
+ * 1 Thread 3567.1 0x011aaf9c in swtch_pri () at /build/buildd-eglibc_2.11.2-7-hurd-i386-6JVoJz/eglibc-2.11.2/build-tree/hurd-i386-libc/mach/swtch_pri.S:2
+ (gdb) bt
+ #0 0x011aaf9c in swtch_pri () at /build/buildd-eglibc_2.11.2-7-hurd-i386-6JVoJz/eglibc-2.11.2/build-tree/hurd-i386-libc/mach/swtch_pri.S:2
+ #1 0x011ac824 in __spin_lock_solid (lock=0x131e8e0) at spin-solid.c:27
+ #2 0x011aca1d in __mutex_lock_solid (lock=0x131e8e0) at mutex-solid.c:31
+ #3 0x0122dd0b in __mutex_lock (oldmem=0x8076458, bytes=94) at ../mach/lock-intern.h:89
+ #4 __libc_realloc (oldmem=0x8076458, bytes=94) at malloc.c:3814
+ #5 0x0121de62 in _IO_vasprintf (result_ptr=0x15f40c0, format=0x13098a8 "%s%s%s:%u: %s%sUnexpected error: %s.\n", args=0x15f3c9c "") at vasprintf.c:86
+ #6 0x01206d1b in ___asprintf (string_ptr=0x15f40c0, format=0x13098a8 "%s%s%s:%u: %s%sUnexpected error: %s.\n") at asprintf.c:37
+ #7 0x011e2fc8 in __assert_perror_fail (errnum=19, file=0x1305a98 "../sysdeps/mach/hurd/fork.c", line=466, function=0x1305acf "__fork") at assert-perr.c:62
+ #8 0x012586c8 in __fork () at ../sysdeps/mach/hurd/fork.c:466
+ #9 0x011f92e9 in do_system (line=0x15f42dc "/bin/stty sane > /dev/ttypa") at ../sysdeps/posix/system.c:119
+ #10 0x0105bea6 in ?? () from /usr/lib/libexpect.so.5.44.1.15
+ #11 0x0105bf6d in ?? () from /usr/lib/libexpect.so.5.44.1.15
+ #12 0x0105c229 in exp_getptyslave () from /usr/lib/libexpect.so.5.44.1.15
+ #13 0x0103e4b2 in ?? () from /usr/lib/libexpect.so.5.44.1.15
+ #14 0x01087d79 in ?? () from /usr/lib/libtcl8.5.so.0
+ #15 0x01088beb in ?? () from /usr/lib/libtcl8.5.so.0
+ #16 0x0108826a in Tcl_EvalEx () from /usr/lib/libtcl8.5.so.0
+ #17 0x0108985f in TclEvalObjEx () from /usr/lib/libtcl8.5.so.0
+ [...]
+ (gdb) bt full
+ #0 0x011aaf9c in swtch_pri () at /build/buildd-eglibc_2.11.2-7-hurd-i386-6JVoJz/eglibc-2.11.2/build-tree/hurd-i386-libc/mach/swtch_pri.S:2
+ No locals.
+ #1 0x011ac824 in __spin_lock_solid (lock=0x131e8e0) at spin-solid.c:27
+ No locals.
+ #2 0x011aca1d in __mutex_lock_solid (lock=0x131e8e0) at mutex-solid.c:31
+ No locals.
+ #3 0x0122dd0b in __mutex_lock (oldmem=0x8076458, bytes=94) at ../mach/lock-intern.h:89
+ No locals.
+ #4 __libc_realloc (oldmem=0x8076458, bytes=94) at malloc.c:3814
+ ar_ptr = <value optimized out>
+ nb = 104
+ newp = 0x68
+ oldp = 0x8076450
+ oldsize = 104
+ __func__ = "__libc_realloc"
+ #5 0x0121de62 in _IO_vasprintf (result_ptr=0x15f40c0, format=0x13098a8 "%s%s%s:%u: %s%sUnexpected error: %s.\n", args=0x15f3c9c "") at vasprintf.c:86
+ sf = {_sbf = {_f = {_flags = -72515584,
+ _IO_read_ptr = 0x8076458 "expect: ../sysdeps/mach/hurd/fork.c:466: __fork: Unexpected error: (os/kern) urefs overflow.\n",
+ _IO_read_end = 0x8076458 "expect: ../sysdeps/mach/hurd/fork.c:466: __fork: Unexpected error: (os/kern) urefs overflow.\n",
+ _IO_read_base = 0x8076458 "expect: ../sysdeps/mach/hurd/fork.c:466: __fork: Unexpected error: (os/kern) urefs overflow.\n",
+ _IO_write_base = 0x8076458 "expect: ../sysdeps/mach/hurd/fork.c:466: __fork: Unexpected error: (os/kern) urefs overflow.\n",
+ _IO_write_ptr = 0x80764b5 "", _IO_write_end = 0x80764bc "\201\004",
+ _IO_buf_base = 0x8076458 "expect: ../sysdeps/mach/hurd/fork.c:466: __fork: Unexpected error: (os/kern) urefs overflow.\n",
+ _IO_buf_end = 0x80764bc "\201\004", _IO_save_base = 0x0, _IO_backup_base = 0x0, _IO_save_end = 0x0, _markers = 0x0, _chain = 0x0, _fileno = 20046008,
+ _flags2 = 0, _old_offset = 23018464, _cur_column = 0, _vtable_offset = 49 '1', _shortbuf = "\001", _lock = 0x0, _offset = 85643859813466072,
+ _codecvt = 0x1304583, _wide_data = 0x15f3bc0, _freeres_list = 0x0, _freeres_buf = 0x15f3c58, _freeres_size = 0, _mode = -1,
+ _unused2 = "\240;_\001\236D0\001\005\000\000\000\340;_\001(K3\001\000\000\000\000\005\000\000\000\000\000\000\000\250\230\060\001\260\303\031\001"},
+ vtable = 0x131b9c0}, _s = {_allocate_buffer = 0x122cdf0 <__libc_malloc>, _free_buffer = 0x122cd20 <__libc_free>}}
+ ret = <value optimized out>
+ needed = 94
+ #6 0x01206d1b in ___asprintf (string_ptr=0x15f40c0, format=0x13098a8 "%s%s%s:%u: %s%sUnexpected error: %s.\n") at asprintf.c:37
+ done = 1
+ #7 0x011e2fc8 in __assert_perror_fail (errnum=19, file=0x1305a98 "../sysdeps/mach/hurd/fork.c", line=466, function=0x1305acf "__fork") at assert-perr.c:62
+ errbuf = "\334\r", '\000' <repeats 14 times>, "\f\265\032\001\000\000\000\000x\262\004\b\000\000\000\000\000\000\000\000\377\377\377\377 \262\004\b\250\065\063\001\070A_\001k\000\000\000\000\000\000\000ı2\001\002", '\000' <repeats 11 times>"\366, \377\377\377\270\235\004\bk\000\000\000X=_\001\037\343\037\001\377\377\377\377\000\000\000\000s=_\001\361\t\006\001\070A_\001\362\t\006\001\350\t\006\001\000\000\000\000\304B_\001\350\t\006\001\330\377_\001\033\000\000\000)\036\024\001\364\267\025\001x=_\001Bq\022\001\000\000\000\000\350:\b\b\230=_\001\364\267\025\001X\313\031\b S\005\b\230=_\001\004\334\f\001X\313\031\b\000\022\030\b\300L\005\b\364\267\025\001\370\021\030\b S\005\b\bB_\001\a\365\f\001 S\005\b\320\021\030\b\001\000\000\000\274A_\001,\316\024\001\001\000\000\000\001\000\000\000\344"...
+ buf = <value optimized out>
+ #8 0x012586c8 in __fork () at ../sysdeps/mach/hurd/fork.c:466
+ newproc = 122
+ sigthread_refs = 4
+ portnames = 0x63000
+ porttypes = 0x64000
+ sigthread = 130
+ state = {gs = 1, fs = 18236712, es = 20390776, ds = 17004532, edi = 1, esi = 143348, ebp = 23020160, esp = 0, ebx = 23020088, edx = 23020016,
+ ecx = 23020028, eax = 3966371413, eip = 23020088, cs = 18236712, efl = 0, uesp = 20138312, ss = 18488015}
+ newtask = 121
+ thread = 139
+ thread_refs = 65534
+ statecount = <value optimized out>
+ nportnames = 142
+ nporttypes = 142
+ env = {{__jmpbuf = {20037620, 23068628, 23020252, 23020128, 23019736, 19231503}, __mask_was_saved = 0, __saved_mask = 4222451713}}
+ pid = <value optimized out>
+ err = EKERN_INVALID_ADDRESS
+ __PRETTY_FUNCTION__ = "__fork"
+ ss = 0x1376808
+ threads = 0x65000
+ nthreads = 2
+ stopped = 0
+ i = 2
+ #9 0x011f92e9 in do_system (line=0x15f42dc "/bin/stty sane > /dev/ttypa") at ../sysdeps/posix/system.c:119
+ status = <value optimized out>
+ save = <value optimized out>
+ pid = <value optimized out>
+ sa = {__sigaction_handler = {sa_handler = 0x1, sa_sigaction = 0x1}, sa_mask = 524288, sa_flags = 0}
+ omask = 0
+ [...]
+
+`fork` failed here:
+
+ 458 /* We have one extra user reference created at the beginning of this
+ 459 function, accounted for by mach_port_names (and which will thus be
+ 460 accounted for in the child below). This extra right gets consumed
+ 461 in the child by the store into _hurd_sigthread in the child fork. */
+ 462 if (thread_refs > 1 &&
+ 463 (err = __mach_port_mod_refs (newtask, ss->thread,
+ 464 MACH_PORT_RIGHT_SEND,
+ 465 thread_refs)))
+ 466 LOSE;
+
+This is in the parent, before signal thread setup, registering with the
+proc server, and starting the new process.
+
+The error is 19, `EKERN_UREFS_OVERFLOW`.
+
+(This is likely also the reason why the error path did not execute
+successfully.)
+
+[[!tag open_issue_glibc]]