Date: Sat, 31 Aug 1996 00:56:56 +1000 From: Bruce Evans <bde@zeta.org.au> To: julian@whistle.com, pst@shockwave.com Cc: hackers@FreeBSD.org Subject: Re: gdb remote Message-ID: <199608301456.AAA07864@godzilla.zeta.org.au>
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>I don't know why yours is hellishly slow, it sounds like the tty code >is not syncing properly or you're getting lots of retries. In addition, >all the breakpoints and continues and steps work fine for me. The retries might be caused by UART bugs. sio context switches the UART registers on every `cn' i/o so that TIOCSETAs on the debugger port can be single stepped and don't wipe out the debugger's settings. This works OK at typing speeds but can't work for input at high speeds unless the context switching is a no-op. There are UART bugs that cause harmful side effects even when the context switching should be a no-op. > booting -g I can get the kernel to fall into the appropriate debugger > by hitting ctl-alt-esc on the keyboard. The -current gdb works here only after booting with -dg. I get checksum errors after ctl-sysreq. > it's hellishly slow..... > for example.. > the folloing took 1 minute to print out.... > (kgdb) bt > #0 0xf01adf7d in Debugger () > #1 0xf01caf31 in sgetc () > #2 0xf01c6737 in pcvt_timeout () > #3 0xf01092a4 in softclock () This takes a second or two here. Still too long. 115200 bps should make it fast enough for a command line debugger. Bruce
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