Re: CONFIG_VGACON_SOFT_SCROLLBACK crashes 2.6.17

[Antonino A. Daplas]

Al Boldi wrote:
> Antonino A. Daplas wrote:
>> Al Boldi wrote:
>>> Enabling CONFIG_VGACON_SOFT_SCROLLBACK causes random fatal system
>>> freezes.
>>>
>>> Especially, ping 10.1 -A easily causes a complete system hang during
>>> scroll.
>>>
>>> Is there an easy way to fix this, other than disabling the option?
>> I can't duplicate your problem. Did it ever work before?
> 
> This option did not exist before 2.6.17.

I meant if you tried any of the -rc kernels. 

Anyway, can you try the patch below.  It's a debugging patch and
it will slow down the console.

If the system hang disappears, remove the line

    while (i--);

in include/linux/vt_buffer.h.  This line is introduced by
the patch below.

Let me know at what point it worked, or whether it worked at all.

> 
>> Can you send me you kernel config?
> 
> Attached below.
> 
> BTW, is there any chance to patch your savagefb to support VIA/S3 UniChrome?
> 

If someone posts a patch to lkml or fbdev-devel, why not?  But a separate
driver is probably better as the 2 are very different.

Tony

diff --git a/include/linux/vt_buffer.h b/include/linux/vt_buffer.h
index 057db7d..e9b6064 100644
--- a/include/linux/vt_buffer.h
+++ b/include/linux/vt_buffer.h
@@ -20,11 +20,21 @@ #endif
 
 #ifndef VT_BUF_HAVE_RW
 #define scr_writew(val, addr) (*(addr) = (val))
-#define scr_readw(addr) (*(addr))
-#define scr_memcpyw(d, s, c) memcpy(d, s, c)
-#define scr_memmovew(d, s, c) memmove(d, s, c)
-#define VT_BUF_HAVE_MEMCPYW
-#define VT_BUF_HAVE_MEMMOVEW
+//#define scr_readw(addr) (*(addr))
+
+static inline u16 scr_readw(volatile const u16 *addr)
+{
+    int i = 10000;
+    u16 val = *addr;
+
+    while (i--);
+    return val;
+}
+    
+//#define scr_memcpyw(d, s, c) memcpy(d, s, c)
+//#define scr_memmovew(d, s, c) memmove(d, s, c)
+#undef VT_BUF_HAVE_MEMCPYW
+#undef VT_BUF_HAVE_MEMMOVEW
 #endif
 
 #ifndef VT_BUF_HAVE_MEMSETW
-
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