When browsing web-pages which contain a lot of images (e.g. google's image search) I get frequent crashes with the following backtrace:

#0  kgem_trim_vma_cache (kgem=0x8c9fee8) at kgem.c:1920
#1  0x00444eaf in kgem_bo_map (kgem=0x8c9fee8, bo=0xd892298, prot=3) at kgem.c:1943
#2  0x0046cdf8 in sna_replace (sna=0x8c9fdb0, pixmap=0xa6bb718, bo=0xd892298, src=0xde65040, stride=748) at sna_io.c:455
#3  0x00457860 in sna_pixmap_move_to_gpu (pixmap=0xa6bb718) at sna_accel.c:1173
#4  0x0045c11f in sna_pixmap_force_to_gpu (pixmap=0xa6bb718) at sna_accel.c:1112
#5  0x0046d908 in sna_render_pixmap_bo (sna=0x8c9fdb0, channel=0xbf81c7e8, pixmap=0xa6bb718, x=278, y=65, w=187, 
    h=<optimized out>, dst_x=555, dst_y=0) at sna_render.c:504
#6  0x0048aded in gen3_composite_picture (sna=0x8c9fdb0, picture=0xdd28a00, op=0xbf81c7bc, channel=0xbf81c7e8, x=278, y=65, 
    w=184, h=8, dst_x=555, dst_y=0) at gen3_render.c:2128
#7  0x00492a99 in gen3_render_composite (tmp=0xbf81c7bc, height=8, width=184, dst_y=0, dst_x=555, mask_y=0, mask_x=0, 
    src_y=<optimized out>, src_x=278, dst=0xa6bc5b0, mask=0x0, src=0xdd28a00, op=1 '\001', sna=0x8c9fdb0)
    at gen3_render.c:2414
#8  gen3_render_composite (sna=0x8c9fdb0, op=1 '\001', src=0xdd28a00, mask=0x0, dst=0xa6bc5b0, src_x=278, src_y=65, 
    mask_x=0, mask_y=0, dst_x=555, dst_y=0, width=184, height=8, tmp=0xbf81c7bc) at gen3_render.c:2339
#9  0x004615b9 in sna_composite (op=1 '\001', src=0xdd28a00, mask=0x0, dst=0xa6bc5b0, src_x=278, src_y=65, mask_x=0, 
    mask_y=0, dst_x=555, dst_y=0, width=184, height=8) at sna_composite.c:462
#10 0x08156aaf in damageComposite (op=1 '\001', pSrc=0xdd28a00, pMask=0x0, pDst=0xa6bc5b0, xSrc=278, ySrc=65, xMask=0, 
    yMask=0, xDst=555, yDst=0, width=184, height=8) at damage.c:569
#11 0x0814965b in CompositePicture (op=<optimized out>, pSrc=0xdd28a00, pMask=0x0, pDst=0xa6bc5b0, xSrc=278, ySrc=65, 
    xMask=0, yMask=0, xDst=555, yDst=0, width=184, height=8) at picture.c:1647
#12 0x0814ec1b in ProcRenderComposite (client=0x8f9cd58) at render.c:728
#13 0x08149ed4 in ProcRenderDispatch (client=0x8f9cd58) at render.c:2063
#14 0x080760f5 in Dispatch () at dispatch.c:447
#15 0x0806433a in main (argc=6, argv=0xbf81cbc4, envp=0xbf81cbe0) at main.c:287

intel i945GM
intel-git (2.17.0-130-g19c184b)
libdrm-2.4.29
linux-3.1.5
xorg 1.11.1