Bug 499063 - [RHEL5] undefined reference to `__udivdi3'
[RHEL5] undefined reference to `__udivdi3'
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: kernel (Show other bugs)
All Linux
low Severity medium
: rc
: ---
Assigned To: Cong Wang
Red Hat Kernel QE team
Depends On:
Blocks: 533192 526775
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Reported: 2009-05-04 23:10 EDT by Linda Wang
Modified: 2013-09-29 22:08 EDT (History)
2 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2010-03-30 03:40:30 EDT
Type: ---
Regression: ---
Mount Type: ---
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Verified Versions:
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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Description Linda Wang 2009-05-04 23:10:35 EDT
Description of problem:
Since some architectures don't support __udivdi3().

Version-Release number of selected component (if applicable):

How reproducible:
compile the rhel5 kernel source.

Additional info: 
upstream commit id:

diff --git a/include/linux/time.h b/include/linux/time.h
index 2091a19..d32ef0a 100644 (file)
--- a/include/linux/time.h
+++ b/include/linux/time.h
@@ -174,6 +174,10 @@ static inline void timespec_add_ns(struct timespec *a, u64 ns)
        ns += a->tv_nsec;
        while(unlikely(ns >= NSEC_PER_SEC)) {
+               /* The following asm() prevents the compiler from
+                * optimising this loop into a modulo operation.  */
+               asm("" : "+r"(ns));
                ns -= NSEC_PER_SEC;
Comment 2 Linda Wang 2009-05-08 00:19:56 EDT
more description as request by peer review process:

per developer:

When I built the latest rhel5 kernel, I got the following compile error:

kernel/built-in.o: In function `getnstimeofday':
(.text+0xb6ae): undefined reference to `__umoddi3'
kernel/built-in.o: In function `getnstimeofday':
(.text+0xb6ce): undefined reference to `__udivdi3'

This is due to that gcc optimizes the loop in timespec_add_ns() into mod
operation, but i686 doesn't support 64-bit integer mod operation, so gcc
will use libgcc's __umoddi3() and __udivdi3.

The patch below prevents gcc to do this optimization.

Upstream Status of this patch:
This patch was already merged into upstream as commit
Comment 3 RHEL Product and Program Management 2009-09-25 13:37:30 EDT
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux maintenance release.  Product Management has requested
further review of this request by Red Hat Engineering, for potential
inclusion in a Red Hat Enterprise Linux Update release for currently deployed
products.  This request is not yet committed for inclusion in an Update
Comment 5 Don Zickus 2009-10-06 15:37:15 EDT
in kernel-2.6.18-168.el5
You can download this test kernel from http://people.redhat.com/dzickus/el5

Please do NOT transition this bugzilla state to VERIFIED until our QE team
has sent specific instructions indicating when to do so.  However feel free
to provide a comment indicating that this fix has been verified.
Comment 8 errata-xmlrpc 2010-03-30 03:40:30 EDT
An advisory has been issued which should help the problem
described in this bug report. This report is therefore being
closed with a resolution of ERRATA. For more information
on therefore solution and/or where to find the updated files,
please follow the link below. You may reopen this bug report
if the solution does not work for you.


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