RHEL7: mlx4 ethernet HW timestamps ioctl will toggle link

Solution In Progress - Updated -

Environment

  • Red Hat Enterprise Linux 7
    • kernel-3.10.0-123.9.3.el7
  • HW time stamping
    • Mellanox mlx4_en v2.0

Issue

  • The adapater will link flap the 1st time ioctl(fd, SIOCSHWT-STAMP, &ifreq) is called for a Mellanox Ethernet card. Subsequent ioctls will not be affected.

Resolution

  • Load all modules and start all processes that call ioctl(fd, SIOCSHWT-STAMP, &ifreq) only at startup.

Root Cause

  • The Mellanox Ethernet driver needs to reset the Adapters port when enabling HW time stamps. The link will therefore go down and up again.

Diagnostic Steps

The following message will be logged in /var/log/messages when the ioctl is called:

[ 3111.460835] mlx4_en: ethX: Changing Time Stamp configuration
[ 3111.470540] mlx4_en: ethX:   frag:0 - size:1526 prefix:0 align:0 stride:1536
[ 3111.534689] mlx4_en: ethX: Link Down
[ 3111.767914] mlx4_en: ethX: Link Up

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