Messages in this thread | | | Date | Tue, 25 Aug 2015 11:02:52 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH v2 0/6] perf: Introduce extended syscall error reporting |
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* Johannes Berg <johannes@sipsolutions.net> wrote:
> On Mon, 2015-08-24 at 17:32 +0300, Alexander Shishkin wrote: > > > This time around, I employed a linker trick to convert the structures > > containing extended error information into integers, which are then > > made to look just like normal error codes so that IS_ERR_VALUE() and > > friends would still work correctly on them. So no extra pointers in > > the struct perf_event or anywhere else; the extended error codes are > > passed around like normal error codes. They only need to be converted > > in syscalls' topmost return statements. This is done in 1/6. > > For the record, as we discussed separately, I'd love to see this move to more > general infrastructure. In wireless (nl80211), for example, we have a few > hundred (!) callsites returning -EINVAL, mostly based on malformed netlink > attributes, and it can be very difficult to figure out what went wrong; > debugging mostly employs a variation of Hugh's trick.
Absolutely, I suggested this as well earlier today, as the scheduler would like to make use of it in syscalls with extensible ABIs, such as sched_setattr().
If people really like this then we could go farther as well and add a standalone 'extended errors system call' as well (SyS_errno_extended_get()), which would allow the recovery of error strings even for system calls that are not easily extensible. We could cache the last error description in the task struct.
Thanks,
Ingo
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