Bug 613969 - strace doesn't log when you call clock_gettime
Summary: strace doesn't log when you call clock_gettime
Alias: None
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: strace
Version: 6.0
Hardware: All
OS: Linux
Target Milestone: rc
: ---
Assignee: Roland McGrath
QA Contact: qe-baseos-tools-bugs
Depends On:
TreeView+ depends on / blocked
Reported: 2010-07-13 11:55 UTC by edb_unix
Modified: 2011-05-13 12:46 UTC (History)
0 users

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2010-07-13 19:28:10 UTC
Target Upstream Version:

Attachments (Terms of Use)
testprogram (144 bytes, text/plain)
2010-07-13 11:55 UTC, edb_unix
no flags Details
strace of testclock on a 5.4 (5.29 KB, text/plain)
2010-07-13 11:56 UTC, edb_unix
no flags Details
strace of testclock on 6.0 Beta (3.29 KB, text/plain)
2010-07-13 11:57 UTC, edb_unix
no flags Details

Description edb_unix 2010-07-13 11:55:26 UTC
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 11:56:40 UTC
Created attachment 431432 [details]
strace of testclock on a 5.4

Comment 2 edb_unix 2010-07-13 11:57:20 UTC
Created attachment 431433 [details]
strace of testclock on 6.0 Beta

Comment 4 Roland McGrath 2010-07-13 19:28:10 UTC
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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