Date: Tue, 14 Feb 2006 09:47:44 +0100 From: Marius Strobl <marius@alchemy.franken.de> To: Antoine Brodin <antoine.brodin@laposte.net> Cc: freebsd-sparc64@freebsd.org Subject: Re: sparc64/93226: DEBUG_LOCKS (really stack_save()) causes panics on sparc64 Message-ID: <20060214094744.A81690@newtrinity.zeist.de> In-Reply-To: <20060213213719.7767921e.antoine.brodin@laposte.net>; from antoine.brodin@laposte.net on Mon, Feb 13, 2006 at 09:37:19PM %2B0100 References: <200602131150.k1DBo6S1074438@freefall.freebsd.org> <200602131223.51561.jhb@freebsd.org> <20060213193613.547d1b8f.antoine.brodin@laposte.net> <200602131430.11228.jhb@freebsd.org> <20060213213719.7767921e.antoine.brodin@laposte.net>
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On Mon, Feb 13, 2006 at 09:37:19PM +0100, Antoine Brodin wrote: > John Baldwin <jhb@freebsd.org> wrote: > > On Monday 13 February 2006 13:36, Antoine Brodin wrote: > > > John Baldwin <jhb@freebsd.org> wrote: > > > > If there are kernel functions before the assembly ones (dependent on link > > > > order) then this would wrongly bail when it hit those. I think you need > > > > to do what the ddb stack tracing code does which is to lookup the symbol > > > > name and do a bcmp() on the first 4 chars to recognize trapframes. > > > > > > I ran objdump -d on a sparc64 kernel and it looks like tl0_* and tl1_* > > > are always at the beginning of the code, there is some kind of magic. > > > > magic aside, it would be best to use the same algorithm in both places IMO. > > It would also be a lot more intuitive to other folks later on. > > There are 2 reasons why I didn't use db_search_symbol() and > db_symbol_values() : > > - first they aren't reentrant, they use a global variable > db_last_symtab and they can panic if a thread sets db_last_symtab to 0 > while another one is using it. I found this in my mail archive : > %%% > Stopped at X_db_symbol_values+0x18: cmpl $0,0xc(%eax) > db> trace > Tracing pid 34983 tid 100093 td 0xc2e9c640 > X_db_symbol_values(0,c0738214,e84859f4,e84859c4,7c) at X_db_symbol_values+0x18 > db_symbol_values(c0738214,e84859f4,0,c89d19c8,0) at db_symbol_values+0x40 > %%% > It can be fixed easily but I don't have the fix anymore. > You can use linker_ddb_search_symbol() and linker_ddb_symbol_values() > too that are safer. > > - the second reason is performance. if you replace > CTRSTACK(KTR_LOCK, &stack, 0, 1); > by > CTRSTACK(KTR_LOCK, &stack, 0, 0); > in kern_lock.c, i.e. if you print the symbol name in the ktr traces, you > will notice that your box is extremely slow. (you type ls, you wait 4 or 5 > seconds and you have the result) > Can't we just use what's done in support.S and add two dummy symbols to mark the begin and end of the asm functions in question? Marius -- This mail was scanned by AntiVir Milter. This product is licensed for non-commercial use. See www.antivir.de for details.
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