gdb ignoring skas breakpoints?

uml-devel Allan Graves 3 participants 3 messages Aug 27, 2005 – Aug 28, 2005 User-mode Linux (UML)

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Allan Graves

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2005-08-27 01:50 UTC #0 lore raw

Jeff,
I thought i had this thread trace thing several times, but I couldn't get gdb to stop on breakpoints, its like it was ignoring them.... it thought everything was in thread_info.h. And it listed the right code, and i could do like b 26, and it would set a breakpoint for line 26 of the correct function with the correct filename, and then just ignore it.

(gdb) info b

Num Type           Disp Enb Address    What
1   breakpoint     keep y   0x0806f607 in panic at kernel/panic.c:74
2   breakpoint     keep y   0x0805c254 in switch_to_skas at arch/um/kernel/skas/process_kern.c:29
3   breakpoint     keep y   0x081e5ac5 in schedule at thread_info.h:50
4   breakpoint     keep y   0x081e6037 in schedule at kernel/sched.c:2747

Any suggestions?
Allan

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Blaisorblade

2005-08-27 09:30 UTC #1 lore raw

Quoted 6 lines · Allan Graves

Jeff,
I thought i had this thread trace thing several times, but I couldn't
get gdb to stop on breakpoints, its like it was ignoring them.... it
thought everything was in thread_info.h. And it listed the right code, and i could do like b 26, and it would set a breakpoint for line 26 of the correct function with the correct filename, and then just ignore it.

If you break on an exact line, then it may still be that you found a "no-op" line (which means for instance comments, but GCC optimization may make you wonder).

However, apart from that, I've seen that happen too when trying to do things like break panic. I think I've never seen it working. I don't know if Jeff has it working (he's been staying with gdb 5.x to avoid lots of problems in new releases).

However, please first disable TT mode and checks if that changes anything...

Quoted 23 lines

(gdb) info b
Num Type           Disp Enb Address    What
1   breakpoint     keep y   0x0806f607 in panic at kernel/panic.c:74
2   breakpoint     keep y   0x0805c254 in switch_to_skas at
arch/um/kernel/skas/process_kern.c:29
3   breakpoint     keep y   0x081e5ac5 in schedule at thread_info.h:50
4   breakpoint     keep y   0x081e6037 in schedule at kernel/sched.c:2747
Any suggestions?
Allan
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Signature · 23 lines

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Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
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September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices
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Jeff Dike

2005-08-28 13:46 UTC #2 lore raw

Quoted 4 lines · Blaisorblade

However, apart from that, I've seen that happen too when trying to do things like break panic. I think I've never seen it working. I don't know if Jeff has it working (he's been staying with gdb 5.x to avoid lots of problems in new releases).

I'm now suffering with a modern breakpoint-missing gdb just like everyone else. What I do is stick a

	while(stop_here) sleep(1);

at the point where I want to stop, and rebuild and reboot.

When it freezes at the sleep, I attach gdb to it, set stop_here=0, finish my way out of the sleep, and continue debugging from there.

Jeff