On Mon, Jul 11, 2011 at 10:39:35AM +0800, Tiejun Chen wrote: > When enable CONFIG_PREEMPT we will trigger the following call trace: > > BUG: scheduling while atomic: swapper/1/0x10000000 > ... > > krpobe always goes through the following path: > > program_check_exception() > | > + notify_die(DIE_BPT, "breakpoint",...) > | > + kprobe_handler() > | > + preempt_disable(); > + break_handler() <- preempt_enable_no_resched() > + emulate_step() > + preempt_enable_no_resched() > ... > exit > > We should remove unnecessary preempt_enable_no_resched() inside of > break_handler() > since looks longjmp_break_handler() always go the above path.
The current code is correct. Reasoning follows... setjmp_pre_handler() and longjmp_break_handler() are used only for jprobes. In the case of a jprobe, the code flow would be: bp hit -> kprobe_handler() -> preempt_disable() -> setjmp_pre_handler() (not that since this routine returns 1, we skip sstep here) -> jp->entry() -> jprobe_return() -> bp hit -> kprobe_handler() -> preempt_disable() again -> longjmp_break_handler() -> preempt_enable() -> sstep -> preempt_enable() (for the second kprobe_handler() entry). You could verify this with a preempt_count() printk with a CONFIG_PREEMPT=y kernel. > Signed-off-by: Tiejun Chen <tiejun.c...@windriver.com> Nack, sorry :-) Ananth _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
