Messages in this thread | | | Date | Wed, 29 Mar 2017 19:17:14 +0100 | From | Mark Rutland <> | Subject | Re: [PATCH v2 7/8] bus: brcmstb_gisb: add notifier handling |
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On Wed, Mar 29, 2017 at 10:39:11AM -0700, Doug Berger wrote: > On 03/29/2017 03:13 AM, Mark Rutland wrote:
> >> +static int dump_gisb_error(struct notifier_block *self, unsigned long v, > >> + void *p)
> >> + return 0; > > > > I think this should be NOTIFY_OK. > > > I used dump_mem_limit() as a template and didn't catch this (work to > do...). Upon review I think I would prefer NOTIFY_DONE since this call > is opportunistic (i.e. it is taking the opportunity to check whether > additional diagnostic data is available to display) and has no interest > in affecting the overall handling of the event.
That's fine by me.
Does the distinction matter here?
Most notifer users treat NOTIFY_OK and NOTIFY_DONE as equivalent, and notifier_call_chain only terminates when it sees NOTIFY_STOP_MASK.
[...]
> >> + if (list_is_singular(&brcmstb_gisb_arb_device_list)) { > >> + register_die_notifier(&gisb_error_notifier); > >> + atomic_notifier_chain_register(&panic_notifier_list, > >> + &gisb_error_notifier); > > > > I don't think this is quite right. A notifier_block can only be > > registered to one notifier chain at a time, and this has the potential > > to corrupt both chains. > > > A VERY good point thanks for pointing this out. > > > I also think you only need to register the panic notifier. An SError > > should always result in a panic. > > > That was my initial thought as well. However, testing revealed that the > bad mode Oops actually exits the user space process and doesn't reach > the panic so there was no helpful diagnostic message. This may be in > line with your comments about insufficient fatality of failures in PATCH > v2 6/8, but it actually is more in line with our desired behavior for > the aborted write. Setting the notify on die gave us the result we are > looking for, but as noted above I should have created a separate notifier. > > I had hoped that the same approach (i.e. die notifier) would remove the > need for PATCH v2 6/8 as well, but I found that the Unhandled fault > error didn't actually die from user mode.
In my mind it's a bug that we don't treat those errors more fatally.
I'll try to dig into that.
Thanks, Mark.
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