On 10/12/20 11:27 AM, Miroslav Benes wrote:

On Sat, 10 Oct 2020, Jens Axboe wrote:

quoted

On 10/9/20 9:21 AM, Jens Axboe wrote:

quoted

On 10/9/20 2:01 AM, Miroslav Benes wrote:

quoted

On Thu, 8 Oct 2020, Oleg Nesterov wrote:

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On 10/05, Jens Axboe wrote:

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Hi,

The goal is this patch series is to decouple TWA_SIGNAL based task_work
from real signals and signal delivery.

I think TIF_NOTIFY_SIGNAL can have more users. Say, we can move
try_to_freeze() from get_signal() to tracehook_notify_signal(), kill
fake_signal_wake_up(), and remove freezing() from recalc_sigpending().

Probably the same for TIF_PATCH_PENDING, klp_send_signals() can use
set_notify_signal() rather than signal_wake_up().

Yes, that was my impression from the patch set too, when I accidentally 
noticed it.

Jens, could you CC our live patching ML when you submit v4, please? It 
would be a nice cleanup.

Definitely, though it'd be v5 at this point. But we really need to get
all archs supporting TIF_NOTIFY_SIGNAL first. Once we have that, there's
a whole slew of cleanups that'll fall out naturally:

- Removal of JOBCTL_TASK_WORK
- Removal of special path for TWA_SIGNAL in task_work
- TIF_PATCH_PENDING can be converted and then removed
- try_to_freeze() cleanup that Oleg mentioned

And probably more I'm not thinking of right now :-)

Here's the current series, I took a stab at converting all archs to
support TIF_NOTIFY_SIGNAL so we have a base to build on top of. Most
of them were straight forward, but I need someone to fixup powerpc,
verify arm and s390.

But it's a decent start I think, and means that we can drop various
bits as is done at the end of the series. I could swap things around
a bit and avoid having the intermediate step, but I envision that
getting this in all archs will take a bit longer than just signing off
on the generic/x86 bits. So probably best to keep the series as it is
for now, and work on getting the arch bits verified/fixed/tested.

https://git.kernel.dk/cgit/linux-block/log/?h=tif-task_work

Thanks, Jens.

Crude diff for live patching on top of the series is below. Tested only on 
x86_64, but it passes the tests without an issue.

Nice, thanks!

I'm continuing to hone the series, what's really missing so far is arch
review. Most conversions are straight forward, some I need folks to
definitely take a look at (arm, s390). powerpc is also a bit hair right
now, but I'm told that 5.10 will kill a TIF flag there, so that'll make
it trivial once I rebase on that.

Did a few more cleanups on top, series is in the same spot. I'll repost
once the merge window settles down.

-- 
Jens Axboe