How can I set break point on my function and list its source?

Now I can't set bp on WinMain though I can see the disassembly of it,and I can't list the source of WinMain either:

0:000> u WinMain
00401040 55              push    ebp
00401041 8bec            mov     ebp,esp
00401043 6a00            push    0
00401045 e87e0e0000      call    monitormt!g_thread_init (00401ec8)
0040104a 83c404          add     esp,4
0040104d e8700e0000      call    monitormt!gdk_threads_init (00401ec2)
00401052 e8650e0000      call    monitormt!gdk_threads_enter (00401ebc)
00401057 e8d4040000      call    monitormt!select_device (00401530)
0:000> ba WinMain
        ^ Unable to set breakpoint error
The system resets thread contexts after the process
breakpoint so hardware breakpoints cannot be set.
Go to the executable's entry point and set it then.
 'ba WinM开发者_Python百科ain'

How to do it in windbg?

UPDATE

It seems bp works,but why ba doesn't?

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The message displayed by debugger actually explains quite clearly why ba would not work at this point. Instruction ba sets a hardware breakpoint. Hardware breakpoints are set through debug registers. The debug registers are part of the processor context, which is set by OS. You just loaded the process into memory -- all memory layout is ready, but processor context has not been set. If you debugger sets some registry values right now, those changes would not matter, because OS will override all register values while starting executing process.

A software breakpoint (bp) is better here because it works by overwriting instruction at address you specified to INT 3 instruction. Obviously that is not affected by processor context changes, so that works any time, even on initial processor breakpoint.

Workaround is simple -- first make a single step using t instruction, then you can use hardware breakpoints as you like. For execution breakpoint I would recommend to use software breakpoints. You can create any number of software breakpoints, while number of hardware breakpoints is limited to number of debug registers.