Created attachment 117269 [details]
Full stack trace

Occasionally Xorg will crash. I haven't been able to reproduce it consistently. I analysed the core dump from the most recent crash and it appears to be a segfault inside the synaptics driver code.

Here's the frame that raises the segfault signal:

      #9  0x00007fe21b131fde in HandleTouches (hw=0x2c90940, pInfo=0x2c90940) at synaptics.c:3041
              slot = <optimized out>
              para = 0x2d06290
              restart_touches = <optimized out>
              i = 72
              priv = 0x2d06290
              new_active_touches = <optimized out>
              min_touches = <optimized out>

Line 3041 in synaptics.c is as follows:

    if (hw->slot_state[slot] == SLOTSTATE_UPDATE && !restart_touches)

Slot is set to priv->open_slots[i], which seems to be the problem.

    (gdb) print *(priv->open_slots)
    $9 = 0
    (gdb) print i
    $10 = 72
    (gdb) print priv->open_slots[72]
    $11 = 51371952
    (gdb) print hw->slot_state[51371952]
    Cannot access memory at address 0xf088d30

My laptop model is Acer Aspire E5-571-37SY. Let me know if any other information would be helpful.