Re: kernel + gcc 4.1 = several problems

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To: Segher Boessenkool <segher@...>
Cc: Denis Vlasenko <vda.linux@...>, <akpm@...>, Albert Cahalan <acahalan@...>, <linux-kernel@...>, <s0348365@...>, Linus Torvalds <torvalds@...>, <bunk@...>, <mikpe@...>
Date: Friday, January 26, 2007 - 6:05 pm

ALSA + GCC 4.1.1 + -Os is known to be a bad combination on some
arches; see http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27363 .  (I
tripped over it on an ARM target, but my limited understanding of GCC
internals does not allow me to conclude that it is ARM-specific.)  A
patch claiming to fix the bug was integrated into the 4.1 branch, but
my tests with a recent (20070115) gcc-4.1 snapshot indicate that it
has regressed again.

You might also check /proc/cpu/alignment; we have seen the alignment
fixup code trigger for alignment errors in both kernel and userspace.
The default appears to be to IGNORE alignment traps from userspace,
which results in bogus data and potentially a wacky series of system
calls, which could conceivably trigger an oops.  I am told that echo 2
that 3 turns on some sort of logging in addition to the fixup (haven't
pursued this myself).  No idea whether this is relevant to your CPU.

Cheers,
- Michael
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Messages in current thread:
Re: kernel + gcc 4.1 = several problems, Albert Cahalan, (Thu Jan 4, 3:11 am)
Re: kernel + gcc 4.1 = several problems, Segher Boessenkool, (Thu Jan 4, 12:43 pm)
Re: kernel + gcc 4.1 = several problems, Albert Cahalan, (Thu Jan 4, 1:04 pm)
Re: kernel + gcc 4.1 = several problems, Andreas Schwab, (Thu Jan 4, 2:08 pm)
Re: kernel + gcc 4.1 = several problems, Linus Torvalds, (Thu Jan 4, 1:37 pm)
Re: kernel + gcc 4.1 = several problems, Denis Vlasenko, (Sun Jan 7, 12:25 am)
Re: kernel + gcc 4.1 = several problems, Segher Boessenkool, (Sun Jan 7, 11:10 am)
Re: kernel + gcc 4.1 = several problems, Michael K. Edwards, (Fri Jan 26, 6:05 pm)
Re: kernel + gcc 4.1 = several problems, Linus Torvalds, (Sun Jan 7, 12:45 am)
Re: kernel + gcc 4.1 = several problems, Jeff Garzik, (Sun Jan 7, 1:26 am)
Re: kernel + gcc 4.1 = several problems, Segher Boessenkool, (Thu Jan 4, 2:34 pm)
Re: kernel + gcc 4.1 = several problems, Geert Bosch, (Thu Jan 4, 6:02 pm)
Re: kernel + gcc 4.1 = several problems, Segher Boessenkool, (Thu Jan 4, 1:24 pm)
Re: kernel + gcc 4.1 = several problems, Pavel Machek, (Fri Jan 5, 1:17 pm)
Re: kernel + gcc 4.1 = several problems, Segher Boessenkool, (Sat Jan 6, 4:23 am)
Re: kernel + gcc 4.1 = several problems, Linus Torvalds, (Thu Jan 4, 1:47 pm)
Re: kernel + gcc 4.1 = several problems, Al Viro, (Thu Jan 4, 3:10 pm)
Re: kernel + gcc 4.1 = several problems, Segher Boessenkool, (Thu Jan 4, 2:53 pm)