Why sparse does not support context tracking?

Hi,

I tried to instrument my code (a kernel driver) with __must_hold hints and noticed that they don't really work: a definitely broken code caused no errors from sparse.

A test in the "sparse" tree confirmed. Here is the test I used:

static int ctx;

static void must_hold(void) __attribute__((context(ctx,1,1)))

{
    if (ctx)
        ;
}
static void bad_must_hold(void)
{
    must_hold();
}

After a bit of looking I found a commit which removed context tracking from the "sparse":

Author: Johannes Berg <[email protected]> 2008-12-23 10:59:22

Revert the context tracking code

> Do you want to resend your change which revert the context changes? > Make it base on Josh's git's tree and I will merge your changes in my > branch.

Below. Or I can give it to you in git if you prefer. I still think we should redo this in some form so that annotations with different contexts can work properly, but I don't have time to take care of it right now.

johannes

>From ca95b62edf1600a2b55ed9ca0515d049807a84fc Mon Sep 17 00:00:00 2001
From: Johannes Berg <[email protected]>
Date: Tue, 23 Dec 2008 10:53:19 +0100
Subject: [PATCH] Revert context tracking code

So it seems that the code has problems with different contexts. Still, it seems a bit heavy-handed to remove it completely (assuming it worked, of course). The kernel even has a bit of use for it (not much, admittedly: DRBD and aoe).

Is it be possible to reintroduce the code at least for the same context? So that it catches at least some locks not taken?

Regards,
Alex Riesen

It didn't really work. It had a lot of issues that were too big for my little wireless-focused brain :)

johannes

Ah, pity. Wasn't there any hope for it?