Bug 735794

that patch is not enough since srb->region == NULL too, so now trying this patch:

commit 426dc8fe8f45082841773382e24dc42a2d2dc22d
Author: Alon Levy <alevy>
Date:   Mon Sep 5 14:28:14 2011 +0300

    i965: prepare_depthbuffer: fix segfault, rhbz#735794
    
    Also fixes a segfault immediatelly after in the same case, i.e.
    srb->region is also NULL in the run of virtualbox described in
    the bug report in the subject.
    
    Signed-off-by: Alon Levy <alevy>

diff --git a/src/mesa/drivers/dri/i965/brw_misc_state.c b/src/mesa/drivers/dri/i965/brw_misc_state.c
index f7e6e7c..479cf82 100644
--- a/src/mesa/drivers/dri/i965/brw_misc_state.c
+++ b/src/mesa/drivers/dri/i965/brw_misc_state.c
@@ -204,11 +204,11 @@ static void prepare_depthbuffer(struct brw_context *brw)
    struct intel_renderbuffer *drb = intel_get_renderbuffer(fb, BUFFER_DEPTH);
    struct intel_renderbuffer *srb = intel_get_renderbuffer(fb, BUFFER_STENCIL);
 
-   if (drb)
+   if (drb && drb->region)
       brw_add_validated_bo(brw, drb->region->buffer);
    if (drb && drb->hiz_region)
       brw_add_validated_bo(brw, drb->hiz_region->buffer);
-   if (srb)
+   if (srb && srb->region)
       brw_add_validated_bo(brw, srb->region->buffer);
 }

That just makes it fail again later, at intel_renderbuffer_tile_offsets



(gdb) bt
#0  intel_renderbuffer_tile_offsets (irb=0x7f98ceb39ec0, tile_x=0x7f98dddcc898, tile_y=0x7f98dddcc89c)
at intel_fbo.c:659
#1  0x00007f98dcb48dca in brw_update_renderbuffer_surface (unit=0, rb=0x7f98ceb39ec0, brw=0x7f98cc4901e
0) at brw_wm_surface_state.c:480
#2  upload_wm_surfaces (brw=0x7f98cc4901e0) at brw_wm_surface_state.c:588
#3  0x00007f98dcb32729 in brw_upload_state (brw=0x7f98cc4901e0) at brw_state_upload.c:553
#4  0x00007f98dcb20930 in brw_try_draw_prims (max_index=<optimized out>, min_index=<optimized out>, ib=
0x0, nr_prims=1, prim=0x7f98cc4ebaec, arrays=0x7f98cc4ed4d0, ctx=0x7f98cc4901e0) at brw_draw.c:370
#5  brw_draw_prims (ctx=0x7f98cc4901e0, arrays=0x7f98cc4ed4d0, prim=0x7f98cc4ebaec, nr_prims=1, ib=0x0,
 index_bounds_valid=<optimized out>, min_index=0, max_index=15) at brw_draw.c:431
#6  0x00007f98dcc11e28 in vbo_exec_vtx_flush (exec=0x7f98cc4eb800, keepUnmapped=1 '\001') at vbo/vbo_ex
ec_draw.c:390
#7  0x00007f98dcc0b34c in vbo_exec_FlushVertices_internal (exec=0x7f98cc4eb800, unmap=<optimized out>)
at vbo/vbo_exec_api.c:545
#8  0x00007f98dcc0fcbc in vbo_exec_FlushVertices (ctx=0x7f98cc4901e0, flags=<optimized out>) at vbo/vbo
_exec_api.c:996
#9  0x00007f98dcbe685e in _mesa_BindTexture (target=34037, texName=622) at main/texobj.c:1102
#10 0x00007f98ddb09c6a in crUnpack () from /usr/lib/virtualbox/VBoxSharedCrOpenGL.so

So I think the right approach would be to make intel_renderbuffer return NULL when irb->region == NULL. I'll try that next.

Alon

Tried something else, namely: (this patch is for the mesa package, not upstream - upstream broke a line in to to preserve max columns, so it didn't apply to mesa)

From fd46e2c7bee1d0c30a66fdee37f0c7d192322481 Mon Sep 17 00:00:00 2001
From: Alon Levy <alevy>
Date: Mon, 5 Sep 2011 16:38:43 +0300
Subject: [PATCH] i965: prepare_depthbuffer: don't update NULL region'ed
 surface, rhbz#735794

---
 src/mesa/drivers/dri/i965/brw_wm_surface_state.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_wm_surface_state.c b/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
index 89fea9c..8cc1e91 100644
--- a/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
+++ b/src/mesa/drivers/dri/i965/brw_wm_surface_state.c
@@ -439,6 +439,9 @@ brw_update_renderbuffer_surface(struct brw_context *brw,
    uint32_t tile_x, tile_y;
    uint32_t format = 0;
 
+   if (irb->region == NULL)
+      return;
+
    surf = brw_state_batch(brw, 6 * 4, 32, &brw->wm.surf_offset[unit]);
 
    switch (irb->Base.Format) {
-- 
1.7.6.1


And then it failed a bit later at:

(gdb) up
#1  0x00007ffb9f86a729 in brw_upload_state (brw=0x7ffba44901e0) at brw_state_upl
oad.c:553
(gdb) down
#0  emit_depthbuffer (brw=0x7ffba44901e0) at brw_misc_state.c:318
(gdb) bt
#0  emit_depthbuffer (brw=0x7ffba44901e0) at brw_misc_state.c:318
#1  0x00007ffb9f86a729 in brw_upload_state (brw=0x7ffba44901e0) at brw_state_upl
oad.c:553
#2  0x00007ffb9f858930 in brw_try_draw_prims (max_index=<optimized out>, min_ind
ex=<optimized out>, ib=0x0, nr_prims=1, prim=0x7ffba44ebaec, arrays=0x7ffba44ed4
d0, ctx=0x7ffba44901e0) at brw_draw.c:370
#3  brw_draw_prims (ctx=0x7ffba44901e0, arrays=0x7ffba44ed4d0, prim=0x7ffba44eba
ec, nr_prims=1, ib=0x0, index_bounds_valid=<optimized out>, min_index=0, max_ind
ex=15) at brw_draw.c:431
#4  0x00007ffb9f949e38 in vbo_exec_vtx_flush (exec=0x7ffba44eb800, keepUnmapped=
1 '\001') at vbo/vbo_exec_draw.c:390

So now really trying what I suggested at comment 2.

comment 2 was wrong, since glClear's intel implementation relies on intel_get_renderbuffer being non NULL. But combining the two previous patches in comment 1 and comment 3, together with the following patch, fixes the problem:

commit 1ecdae72917f4485bd7fea204d346d05a18ee055
Author: Alon Levy <alevy>
Date:   Mon Sep 5 19:25:19 2011 +0300

    i965: emit_depthbuffer: fix segfault, rhbz#735794
    
    Signed-off-by: Alon Levy <alevy>

diff --git a/src/mesa/drivers/dri/i965/brw_misc_state.c b/src/mesa/drivers/dri/i965/brw_misc_state.c
index 479cf82..f102bc6 100644
--- a/src/mesa/drivers/dri/i965/brw_misc_state.c
+++ b/src/mesa/drivers/dri/i965/brw_misc_state.c
@@ -248,6 +248,9 @@ static void emit_depthbuffer(struct brw_context *brw)
    else
       len = 5;
 
+   if (depth_irb && depth_irb->region == NULL)
+      depth_irb = NULL;
+
    if (!depth_irb && !stencil_irb) {
       BEGIN_BATCH(len);
       OUT_BATCH(_3DSTATE_DEPTH_BUFFER << 16 | (len - 2));

put a scratch build with those three patches:

http://koji.fedoraproject.org/koji/taskinfo?taskID=3325476

Alon

better scratch build - same patches, but release incremented:

http://koji.fedoraproject.org/koji/taskinfo?taskID=3325495

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