On Mon, Aug 06, 2018 at 06:34:36PM +0200, Oleg Nesterov wrote: > On 08/06, Jiri Olsa wrote: > > > > Once the breakpoint was succesfully modified, the attr->disabled > > value is in bp->attr.disabled. So there's no reason to set it > > again, removing that. > > > > Link: http://lkml.kernel.org/n/[email protected] > > Signed-off-by: Jiri Olsa <[email protected]> > > --- > > kernel/events/hw_breakpoint.c | 5 ++--- > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c > > index fb229d9c7f3c..3e560d7609fd 100644 > > --- a/kernel/events/hw_breakpoint.c > > +++ b/kernel/events/hw_breakpoint.c > > @@ -526,10 +526,9 @@ int modify_user_hw_breakpoint(struct perf_event *bp, > > struct perf_event_attr *att > > if (err) > > return err; > > > > - if (!attr->disabled) { > > + if (!attr->disabled) > > perf_event_enable(bp); > > - bp->attr.disabled = 0; > > - } > > + > > Yes, but again, this still looks confusing. > > IMO, we should either remove "bp->attr.disabled = attr->disabled" in > modify_user_hw_breakpoint_check() because bp->attr.disabled is not really > used, or we should set bp->attr.disabled = 1 on failure just for consistency. > > > Hmm... actually ptrace_get_dr7() checks ->attr.disabled, so we can hit > WARN_ON(second_pass) in ptrace_write_dr7() in case when attr.disabled is > falsely 0 because modify_user_hw_breakpoint_check() failed before?
hum, I can't see how modify_user_hw_breakpoint_check could falsely set disabled new attr stuff is copied once all checks passed jirka
