tiejun.chen wrote: > Ananth N Mavinakayanahalli wrote: >> 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 :-) > > You're right. > > When use EXC_LEVEL_EXCEPTION_PROLOG for Critical/Machine check, if the > exception > came from kernel mode, we copy thread_info flags, *preempt*, and task pointer > from the process thread_info. So here I steal EXC_LEVEL_EXCEPTION_PROLOG for > Program Exception, preempt count would be corrupted incorrectly.
Looks I miss the specific return-from-program-exc to restore those necessary thread information like we did for debug exception with ret_from_debug_exc when use EXC_LEVEL_EXCEPTION_PROLOG for debug exception. Will update this on v3. Tiejun > > Thanks > Tiejun > >> Ananth >> > > _______________________________________________ > Linuxppc-dev mailing list > Linuxppc-dev@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/linuxppc-dev > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
