Re: VGA emulation in BOCHS

On Fri, Oct 19, 2012 at 06:42:04PM +0200, Stanislav wrote:
> 
> When you did it correctly, only the cpu0 thread increments the timer tick.
> Then it checks if one of the timers has expired and if one did, it calls the
> associated timer handler. The other cpus should never call the timer code.
> The X11 gui code runs in the main thread and a timer call from the cpu0
> thread could make it crash. You should have a look at the wx code and it's
> multi-threading implementation. The gui thread and the simulation thread use
> an event queue for the thread-safe communication.

I got this traceback a while ago:

#0  0x00007f7fede06ce5 in ?? () from /usr/lib/libpthread.so.1
#1  0x00007f7fede070e8 in ?? () from /usr/lib/libpthread.so.1
#2  0x00007f7feda9e659 in ?? () from /usr/lib/libc.so.12
#3  0x00007f7feda9ea59 in malloc () from /usr/lib/libc.so.12
#4  0x00007f7fedad9854 in strdup () from /usr/lib/libc.so.12
#5  0x00007f7fedacf36b in __vfprintf_unlocked () from /usr/lib/libc.so.12
#6  0x00007f7fedac8e43 in sprintf () from /usr/lib/libc.so.12
#7  0x00007f7feb6052f6 in bx_x_gui_c::show_ips(unsigned int) () from /usr/pkg/lib/bochs/plugins/libbx_x.so
#8  0x0000000000440351 in bx_signal_handler(int) ()
#9  <signal handler called>
#10 0x00007f7fede07355 in pthread_mutex_lock () from /usr/lib/libpthread.so.1
#11 0x00007f7feda9d6ad in ?? () from /usr/lib/libc.so.12
#12 0x00007f7feda9f7f9 in free () from /usr/lib/libc.so.12
#13 0x00007f7ff164b643 in _XEventsQueued () from /usr/X11R7/lib/libX11.so.7
#14 0x00007f7ff1634dbc in XCopyPlane () from /usr/X11R7/lib/libX11.so.7
#15 0x00007f7feb6068c8 in bx_x_gui_c::text_update(unsigned char*, unsigned char*, unsigned long, unsigned long, bx_vga_tminfo_t) () from /usr/pkg/lib/bochs/plugins/libbx_x.so
#16 0x00007f7fd6e0afbd in bx_vga_c::update() () from /usr/pkg/lib/bochs/plugins/libbx_vga.so
#17 0x00007f7fd6e0cddd in bx_vga_c::timer_handler(void*) () from /usr/pkg/lib/bochs/plugins/libbx_vga.so
#18 0x000000000045a373 in bx_virt_timer_c::periodic(unsigned long) ()
#19 0x000000000045ae2e in bx_virt_timer_c::timer_handler() ()
#20 0x0000000000451c8d in bx_pc_system_c::countdownEvent() ()
#21 0x000000000046c9db in BX_CPU_C::handleAsyncEvent() ()
#22 0x000000000046d50a in BX_CPU_C::cpu_loop() ()
#23 0x000000000045edcc in bx_dbg_continue_command ()
#24 0x00000000004642c6 in bxparse ()
#25 0x000000000045d241 in bx_dbg_user_input_loop() ()
#26 0x000000000045f0d8 in bx_dbg_main() ()
#27 0x000000000044229e in bx_begin_simulation(int, char**) ()
#28 0x00000000004d6972 in bx_config_interface(int) ()
#29 0x00000000004d6b80 in bx_config_interface(int) ()
#30 0x00000000004d6f75 in ci_callback(void*, ci_command_t) ()
#31 0x00000000004d1310 in bx_real_sim_c::configuration_interface(char const*, ci_command_t) ()
#32 0x0000000000441fd1 in bxmain() ()
#33 0x000000000043f282 in ___start ()

this deadlocked because sprintf() uses gtoa() (I think that is the name) in order
to convert FP values - and that ends up in malloc() which isn't signal safe.
However the code will also re-enter X from the signal handler (to display IPS)
which is also not allowed.


	David

-- 
David Laight: [email protected]

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