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Bug 613969 - strace doesn't log when you call clock_gettime
strace doesn't log when you call clock_gettime
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: strace (Show other bugs)
All Linux
low Severity medium
: rc
: ---
Assigned To: Roland McGrath
Depends On:
  Show dependency treegraph
Reported: 2010-07-13 07:55 EDT by edb_unix
Modified: 2011-05-13 08:46 EDT (History)
0 users

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2010-07-13 15:28:10 EDT
Type: ---
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
testprogram (144 bytes, text/plain)
2010-07-13 07:55 EDT, edb_unix
no flags Details
strace of testclock on a 5.4 (5.29 KB, text/plain)
2010-07-13 07:56 EDT, edb_unix
no flags Details
strace of testclock on 6.0 Beta (3.29 KB, text/plain)
2010-07-13 07:57 EDT, edb_unix
no flags Details

  None (edit)
Description edb_unix 2010-07-13 07:55:26 EDT
Created attachment 431431 [details]

Description of problem:
Strace doesn't show when you call clock_gettime. If we compare this with our 5.4 machine where it shows.

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

How reproducible:

Steps to Reproduce:
1. Program:
$ cat testclock.c
#include <time.h>
#include <stdio.h>

int main(void)
  int intRet;
  struct timespec res;

  intRet = clock_gettime(CLOCK_REALTIME, &res);

2. gcc -o testclock -lrt testclock.c

3. strace ./testclock

Actual results:
A strace without any information about calling clock_gettime

Expected results:
Strace should get a result similair to the below (taken from a Red Hat Enterprise 5.4 environment):
clock_gettime(CLOCK_REALTIME, {1279021215, 132738000}) = 0

Additional info:
See attachment for the whole strace results.
Comment 1 edb_unix 2010-07-13 07:56:40 EDT
Created attachment 431432 [details]
strace of testclock on a 5.4
Comment 2 edb_unix 2010-07-13 07:57:20 EDT
Created attachment 431433 [details]
strace of testclock on 6.0 Beta
Comment 4 Roland McGrath 2010-07-13 15:28:10 EDT
There is no bug here.  The clock_gettime call on x86_64 can now sometimes work via the kernel-supplied vDSO without making a syscall.  strace can't trace the call into the vDSO, since it's just user-mode code (albeit kernel-supplied).

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