Date: Tue, 24 Jan 2012 15:54:24 +0400 From: Gleb Smirnoff <glebius@FreeBSD.org> To: Andriy Gapon <avg@FreeBSD.org> Cc: current@FreeBSD.org Subject: Re: new panic in cpu_reset() with WITNESS Message-ID: <20120124115424.GX16676@glebius.int.ru> In-Reply-To: <4F1D9128.3030501@FreeBSD.org> References: <4F1ABFF3.9090305@FreeBSD.org> <20120122163539.GF16676@glebius.int.ru> <4F1D18A5.8010006@FreeBSD.org> <20120123130743.GI16676@glebius.int.ru> <4F1D6830.60602@FreeBSD.org> <20120123162410.GN16676@glebius.int.ru> <20120123162606.GO16676@FreeBSD.org> <4F1D8E2B.30800@FreeBSD.org> <20120123164659.GQ16676@glebius.int.ru> <4F1D9128.3030501@FreeBSD.org>
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On Mon, Jan 23, 2012 at 06:56:08PM +0200, Andriy Gapon wrote:
A> on 23/01/2012 18:46 Gleb Smirnoff said the following:
A> > On Mon, Jan 23, 2012 at 06:43:23PM +0200, Andriy Gapon wrote:
A> > A> > db> bt
A> > A> > Tracing pid 1 tid 100001 td 0xfffffe0001d5e000
A> > A> > kdb_enter() at kdb_enter+0x3b
A> > A> > panic() at panic+0x1c7
A> > A> > _mtx_lock_spin_flags() at _mtx_lock_spin_flags+0x10f
A> > A> > cnputs() at cnputs+0x7a
A> > A> > vprintf() at vprintf+0xcb
A> > A> > printf() at printf+0x67
A> > A> > db_putc() at db_putc+0x81
A> > A>
A> > A> Ah, db_putc does something different from what I expected.
A> > A> Can you hack it to never use printf?
A> >
A> > Just cut printfs from db_putc()?
A>
A> Make the following condition be always false:
A>
A> if (!kdb_active || ddb_use_printf) {
A>
A> E.g.:
A>
A> if (0) {
With this change + s/printf/db_printf/ in subr_witness.c I've
got the following during reboot:
Rebooting...
lllock order reversal:
1st 0xffffffff80937140 smp rendezvous (smp rendezvous) @ /usr/src/head/sys/kern/kern_shutdown.c:542
2nd 0xffffffff80b13280 syscons video lock (syscons video lock) @ /usr/src/head/sys/dev/syscons/syscons.c:1921
panic: mtx_lock_spin: recursed on non-recursive mutex cnputs_mtx @ /usr/src/head/sys/kern/kern_cons.c:500
cpuid = 0
KDB: enter: panic
[ thread pid 1 tid 100001 ]
Stopped at kdb_enter+0x3b: movq $0,0x5159f2(%rip)
db> bt
Tracing pid 1 tid 100001 td 0xfffffe0001d5e000
kdb_enter() at kdb_enter+0x3b
panic() at panic+0x1c7
_mtx_lock_spin_flags() at _mtx_lock_spin_flags+0x10f
cnputs() at cnputs+0x7a
putchar() at putchar+0x11f
kvprintf() at kvprintf+0x83
vprintf() at vprintf+0x85
printf() at printf+0x67
kdb_backtrace() at kdb_backtrace+0x2d
_witness_debugger() at _witness_debugger+0x2c
witness_checkorder() at witness_checkorder+0x854
_mtx_lock_spin_flags() at _mtx_lock_spin_flags+0x99
scrn_update() at scrn_update+0x41c
sc_cnputc() at sc_cnputc+0x46
cnputc() at cnputc+0x4c
db_putc() at db_putc+0x4d
kvprintf() at kvprintf+0x83
db_printf() at db_printf+0x86
witness_checkorder() at witness_checkorder+0x773
_mtx_lock_spin_flags() at _mtx_lock_spin_flags+0x99
sc_puts() at sc_puts+0x97
sc_cnputc() at sc_cnputc+0x3e
cnputc() at cnputc+0x4c
db_putc() at db_putc+0x4d
kvprintf() at kvprintf+0x83
db_printf() at db_printf+0x86
witness_checkorder() at witness_checkorder+0x773
_mtx_lock_spin_flags() at _mtx_lock_spin_flags+0x99
uart_cnputc() at uart_cnputc+0x3e
cnputc() at cnputc+0x4c
cnputs() at cnputs+0x26
putchar() at putchar+0x11f
kvprintf() at kvprintf+0x83
vprintf() at vprintf+0x85
printf() at printf+0x67
cpu_reset() at cpu_reset+0x81
kern_reboot() at kern_reboot+0x3a5
sys_reboot() at sys_reboot+0x42
amd64_syscall() at amd64_syscall+0x39e
Xfast_syscall() at Xfast_syscall+0xf7
--- syscall (55, FreeBSD ELF64, sys_reboot), rip = 0x40ea3c, rsp = 0x7fffffffd6d8, rbp = 0x49 ---
db>
--
Totus tuus, Glebius.
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