System Environment:
--------------------------
Platform: Broadwell
Libdrm:		(master)libdrm-2.4.52-10-g1cb5fc706cf5913d9dee33c939f65a23ecea17a5
Mesa:		(master)159cec9dec2320d821d388c0df8140c7705b6e0b
Xserver:	(master)xorg-server-1.15.99.901-204-g901fbfbbbd71c0d82080957f8ba09eebbc786f2b
Xf86_video_intel:(master)2.99.911-44-g3310ee89c1f1a663de5f5b12b8125809a213996f
Cairo:		(master)bb17403622e9ea474017e0039af8ee48b2b285db
Libva:		(staging)960352aaf1e11891a533ce2c98b16edde24d6851
Libva_intel_driver:(staging)150f67c67bd92cd201b75a92388fe3a63b00cd8a
Kernel:	(drm-intel-nightly) 7cd8b823493acc320c7db9112de9d4e21c6dbd11

Bug detailed description:
-----------------------------
Following spec_OpenGL_1.1_draw-pixels_samples=* cases segfault on Broadwell with Mesa master branch, but work well on Haswell.
spec_OpenGL_1.1_draw-pixels_samples=2
spec_OpenGL_1.1_draw-pixels_samples=4
spec_OpenGL_1.1_draw-pixels_samples=6
spec_OpenGL_1.1_draw-pixels_samples=8
spec_OpenGL_1.4_copy-pixels_samples=2
spec_OpenGL_1.4_copy-pixels_samples=4
spec_OpenGL_1.4_copy-pixels_samples=6
spec_OpenGL_1.4_copy-pixels_samples=8

run ./bin/draw-pixels -samples=2 -auto
output
Probe depth at (0,0)
  Expected: 0.396078
  Observed: 0.500000
Segmentation fault (core dumped)

(gdb) bt
#0  0x00007ffff403700e in _swrast_unmap_texture (ctx=ctx@entry=0x7ffff3e56038, texObj=0xe95ba0) at swrast/s_texture.c:329
#1  0x00007ffff4037142 in _swrast_unmap_textures (ctx=ctx@entry=0x7ffff3e56038) at swrast/s_texture.c:372
#2  0x00007ffff4006db9 in _swrast_span_render_finish (ctx=0x7ffff3e56038) at swrast/s_context.c:885
#3  0x00007ffff400aad4 in swrast_render_finish (ctx=<optimized out>) at swrast/s_context.h:379
#4  _swrast_DrawPixels (ctx=ctx@entry=0x7ffff3e56038, x=x@entry=0, y=y@entry=0, width=width@entry=150, height=height@entry=150, format=format@entry=6401, type=type@entry=5120,
    unpack=unpack@entry=0x7ffff3e72240, pixels=pixels@entry=0x9d3670) at swrast/s_drawpix.c:698
#5  0x00007ffff41488ff in intelDrawPixels (ctx=0x7ffff3e56038, x=0, y=0, width=150, height=150, format=6401, type=5120, unpack=0x7ffff3e72240, pixels=0x9d3670)
    at intel_pixel_draw.c:155
#6  0x00007ffff3efbd80 in _mesa_DrawPixels (width=150, height=150, format=6401, type=5120, pixels=0x9d3670) at main/drawpix.c:162
#7  0x0000000000403b1f in piglit_display () at /GFX/Test/Piglit/piglit/tests/general/draw-pixels.c:813
#8  0x00007ffff7d0abf3 in run_test (gl_fw=0x605010, argc=1, argv=0x7fffffffe2c8) at /GFX/Test/Piglit/piglit/tests/util/piglit-framework-gl/piglit_winsys_framework.c:76
#9  0x00007ffff7d07127 in piglit_gl_test_run (argc=1, argv=0x7fffffffe2c8, config=0x7fffffffe190) at /GFX/Test/Piglit/piglit/tests/util/piglit-framework-gl.c:191
#10 0x0000000000401517 in main (argc=1, argv=0x7fffffffe2c8) at /GFX/Test/Piglit/piglit/tests/general/draw-pixels.c:60

Reproduce steps:
----------------------------
1. xinit
2. ./bin/draw-pixels -samples=2 -auto