(gdb) core /tmp/core-Xorg-11-0-0-6535-1403345599 
[New LWP 6535]
[New LWP 6540]
warning: Could not load shared library symbols for linux-vdso.so.1.
Do you need "set solib-search-path" or "set sysroot"?
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
warning: no loadable sections found in added symbol-file system-supplied DSO at 0x7fff4ced0000
Core was generated by `/usr/bin/X :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -nov'.
Program terminated with signal 11, Segmentation fault.
#0  0x00007f5e063714ff in sna_mode_redisplay (sna=0x7f5e0be57000) at sna_display.c:6236
6236								    sna_crtc->bo->tiling,
(gdb) bt
#0  0x00007f5e063714ff in sna_mode_redisplay (sna=0x7f5e0be57000) at sna_display.c:6236
#1  0x00007f5e06350282 in sna_scanout_flush (sna=0x7f5e0be57000) at sna_accel.c:17189
#2  0x00007f5e0635109a in sna_accel_block_handler (sna=0x7f5e0be57000, tv=0x7fff4ce144f8) at sna_accel.c:17662
#3  0x00007f5e063747c0 in sna_block_handler (arg=0x7f5e0ca75f00, timeout=0x7fff4ce144f8, read_mask=0x7f5e0c3af8c0 <LastSelectMask>) at sna_driver.c:723
#4  0x00007f5e0bfc1fb4 in BlockHandler (pTimeout=pTimeout@entry=0x7fff4ce144f8, pReadmask=pReadmask@entry=0x7f5e0c3af8c0 <LastSelectMask>) at ../../dix/dixutils.c:387
#5  0x00007f5e0c10d384 in WaitForSomething (pClientsReady=pClientsReady@entry=0x7f5e0cdb2020) at ../../os/WaitFor.c:215
#6  0x00007f5e0bfbd5c1 in Dispatch () at ../../dix/dispatch.c:362
#7  0x00007f5e0bfc168a in dix_main (argc=10, argv=0x7fff4ce14908, envp=<optimized out>) at ../../dix/main.c:294
#8  0x00007f5e09860b45 in __libc_start_main (main=0x7f5e0bfacc00 <main>, argc=10, argv=0x7fff4ce14908, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, 
    stack_end=0x7fff4ce148f8) at libc-start.c:287
#9  0x00007f5e0bfacc2e in _start ()
(gdb) bt full
#0  0x00007f5e063714ff in sna_mode_redisplay (sna=0x7f5e0be57000) at sna_display.c:6236
        arg = {crtc_id = 215802352, fb_id = 32606, flags = 107693376, reserved = 32606, user_data = 140041917617952}
        bo = 0x0
        crtc = 0x7f5e0ca715e0
        sna_crtc = 0x7f5e0ca714e0
        damage = {extents = {x1 = 0, y1 = 0, x2 = 1024, y2 = 1280}, data = 0x0}
        config = 0x7f5e0ca6fc50
        region = 0x7f5e0cdb0ef0
        i = 2
        __FUNCTION__ = "sna_mode_redisplay"
#1  0x00007f5e06350282 in sna_scanout_flush (sna=0x7f5e0be57000) at sna_accel.c:17189
        priv = 0x7f5e0cc0d780
        busy = true
#2  0x00007f5e0635109a in sna_accel_block_handler (sna=0x7f5e0be57000, tv=0x7fff4ce144f8) at sna_accel.c:17662
No locals.
#3  0x00007f5e063747c0 in sna_block_handler (arg=0x7f5e0ca75f00, timeout=0x7fff4ce144f8, read_mask=0x7f5e0c3af8c0 <LastSelectMask>) at sna_driver.c:723
        sna = 0x7f5e0be57000
        tv = 0x7fff4ce144f8
#4  0x00007f5e0bfc1fb4 in BlockHandler (pTimeout=pTimeout@entry=0x7fff4ce144f8, pReadmask=pReadmask@entry=0x7f5e0c3af8c0 <LastSelectMask>) at ../../dix/dixutils.c:387
        i = 0
        j = <optimized out>
#5  0x00007f5e0c10d384 in WaitForSomething (pClientsReady=pClientsReady@entry=0x7f5e0cdb2020) at ../../os/WaitFor.c:215
        i = <optimized out>
        waittime = {tv_sec = 109, tv_usec = 539000}
        wt = 0x7fff4ce14500
        timeout = <optimized out>
        clientsReadable = {fds_bits = {0 <repeats 16 times>}}
        clientsWritable = {fds_bits = {154618823352, 140041919689472, 140041920817920, 696, 140041919818528, 140041908845408, 140734483219984, 140041919818192, 140041919815392, 
            140041919689472, 140041919816464, 696, 0, 140041919820160, 140041920817920, 140041906107383}}
        selecterr = <optimized out>
        nready = 0
        devicesReadable = {fds_bits = {4294967296, 140041920817920, 696, 0, 0, 0, 0, 140041920817920, 0, 140041920823984, 140041920818616, 140041919689472, 140041919833440, 
            140041905512929, 0, 140041920817920}}
        now = <optimized out>
        someReady = 0
#6  0x00007f5e0bfbd5c1 in Dispatch () at ../../dix/dispatch.c:362
        clientReady = 0x7f5e0cdb2020
        result = <optimized out>
        client = <optimized out>
        nready = <optimized out>
        icheck = 0x7f5e0c3a88d0 <checkForInput>
        start_tick = <optimized out>
#7  0x00007f5e0bfc168a in dix_main (argc=10, argv=0x7fff4ce14908, envp=<optimized out>) at ../../dix/main.c:294
        i = <optimized out>
        alwaysCheckForInput = {0, 1}
#8  0x00007f5e09860b45 in __libc_start_main (main=0x7f5e0bfacc00 <main>, argc=10, argv=0x7fff4ce14908, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, 
    stack_end=0x7fff4ce148f8) at libc-start.c:287
        result = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, 6684163115972112476, 140041904638981, 140734483220736, 0, 0, -6684341088269291428, -6737673129596604324}, mask_was_saved = 0}}, 
          priv = {pad = {0x0, 0x0, 0x7f5e0c11fbf0 <__libc_csu_init>, 0x7fff4ce14908}, data = {prev = 0x0, cleanup = 0x0, canceltype = 202505200}}}
---Type <return> to continue, or q <return> to quit---
        not_first_call = <optimized out>
#9  0x00007f5e0bfacc2e in _start ()
No symbol table info available.
(gdb)