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Re: SystemTap for Android - patchset
On 07/06/2016 07:29 AM, Alexander Lochmann wrote:
> So. Let me start.
> First of all, I extracted the patches properly, and attached the files.
> (Btw, I found a third bug. :) )
> FYI, I just fixed the bugs for the kernel versions I'm dealing with,
> because I don't know which other versions are affected as well.
The problem you are trying to fix in your patch "[PATCH 1/3] Definition
of cputime_to_usecs in Linux kernel 3.0 is broken" is interesting. I
don't think you've got quite the right solution. Testing for a kernel
version here works for you, but really isn't a general solution -
depending on arch there could be a kernel in that range with a
reasonable cputime_to_usecs().
====
diff --git a/tapset/linux/task_time.stp b/tapset/linux/task_time.stp
index f86f984..f3c276c 100644
--- a/tapset/linux/task_time.stp
+++ b/tapset/linux/task_time.stp
@@ -27,8 +27,12 @@
* Yet note some kernels (RHEL6) may already have both... */
#if defined(cputime_to_usecs)
#if !defined(cputime_to_msecs)
+#if LINUX_VERSION_CODE <= KERNEL_VERSION(3,0,200) && LINUX_VERSION_CODE
>= KERNEL_VERSION(3,0,0)
+#define cputime_to_msecs(__ct) _stp_div64(NULL,
({cputime_to_usecs(__ct)}), 1000ULL)
+#else
#define cputime_to_msecs(__ct) _stp_div64(NULL,
cputime_to_usecs(__ct), 1000ULL)
#endif
+#endif
/* Kernels before 2.6.37 have cputime_to_msecs, but not usecs. */
#elif defined(cputime_to_msecs)
====
I've got a couple of thoughts here:
- I wonder if we just couldn't always use your workaround (along with a
comment about why we're doing that).
- Here's an untested workaround idea that might work for all kernels:
#define cputime_to_msecs(__ct) \
({ \
unsigned long __usecs = cputime_to_usecs(__ct); \
_stp_div64(NULL, __usecs, 1000ULL); \
})
--
David Smith
dsmith@redhat.com
Red Hat
http://www.redhat.com
256.217.0141 (direct)
256.837.0057 (fax)