Hello.
komal wrote:
> As the discussion was going on about the effects of trapping the
> netpoll queue during KGDBoE debugging, I tried avoiding it. So in
> eth_pre_exception_handler() I did not set net_poll_trap to 1 and did not
> reset it back to 0 in eth_post_exception_handler()
> file drivers/net/kgdboe.c
> static void eth_pre_exception_handler(void)
> {
> /* Increment the module count when the debugger is active */
> if (!kgdb_connected)
> try_module_get(THIS_MODULE);
> // netpoll_set_trap(1);
> }
>
> static void eth_post_exception_handler(void)
> {
> /* decrement the module count when the debugger detaches */
> if (!kgdb_connected)
> module_put(THIS_MODULE);
> // netpoll_set_trap(0);
> }
BTW, I've looked into kgdb_handle_exception() and I think I've spotted
couple of issues with calling these methods:
- the pre_exception() method may be called several times in a row because of
acquirelock label preceding its call -- the code will go back to this label
under some circumstances and therefore netpoll's 'trapping' variable will be
incremented more than once but will only be decremented once upon exit;
- if KGDB hits a disabled breakpoint (can only happen on x86), the code will
jump to the kgdb_restore label bypassing a call to the post_exception()
method.
Obviously, this may render device queue frozen even after KGDB leaves the
exception (because of CONFOG_NETPOLL_TRAP). What about moving the
post_exception() call under kgdb_restore label (that is, after all the CPUs
have quit from KGDB -- which would seem symmetrical to post_exception() call
that is made before all CPUs are stopped) and moving the post_exception() call
before acauirelock label?
WBR, Sergei
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