Hi, On Wed, May 6, 2020 at 9:42 AM Daniel Thompson <[email protected]> wrote: > > Currently there is a small window where a badly timed migration could > cause in_dbg_master() to spuriously return true. Specifically if we > migrate to a new core after reading the processor id and the previous > core takes a breakpoint then we will evaluate true if we read > kgdb_active before we get the IPI to bring us to halt. > > Fix this by checking irqs_disabled() first. Interrupts are always > disabled when we are executing the kgdb trap so this is an acceptable > prerequisite. This also allows us to replace raw_smp_processor_id() > with smp_processor_id() since the short circuit logic will prevent > warnings from PREEMPT_DEBUG. > > Fixes: dcc7871128e9 ("kgdb: core changes to support kdb") > Suggested-by: Will Deacon <[email protected]> > Signed-off-by: Daniel Thompson <[email protected]> > --- > include/linux/kgdb.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/kgdb.h b/include/linux/kgdb.h > index b072aeb1fd78..4d6fe87fd38f 100644 > --- a/include/linux/kgdb.h > +++ b/include/linux/kgdb.h > @@ -323,7 +323,7 @@ extern void gdbstub_exit(int status); > extern int kgdb_single_step; > extern atomic_t kgdb_active; > #define in_dbg_master() \ > - (raw_smp_processor_id() == atomic_read(&kgdb_active)) > + (irqs_disabled() && (smp_processor_id() == atomic_read(&kgdb_active))) > extern bool dbg_is_early; > extern void __init dbg_late_init(void); > extern void kgdb_panic(const char *msg);
Reviewed-by: Douglas Anderson <[email protected]>
