[Jonathan Rosenbaum <mmac_swim@ya...>]

On Mon, 28 Jan 2002, Jeff Dike wrote:

> mmac_swim@... said:
> > .. it loops 12 times, on the 12th try it passes 
> > {count = -65535, wait_lock = {gcc_is_buggy = 0}, wait_list = {
> >     next = 0xa08eda3c, prev = 0xa08eda3c}}
> > to down_read, and then proceeds to panic. 
> 
> This doesn't look like it has anything to do with mtd or jffs at all.
> 
> Can you go into arch/um/Makefile-i386, remove UM_FASTCALL from CFLAGS, 
> and in .config change CONFIG_RWSEM_XCHGADD_ALGORITHM to 
> CONFIG_RWSEM_GENERIC_SPINLOCK and see if that helps?

The testing kernel already had UM_FASTCALL removed, changing the .config
resulted in the compile failing with rwsem-spinlock.c:33: redefinition of
`init_rwsem' (see the end of of the message for the complete log).
 
> Some versions of gcc have a bug which causes register corruption in
> regparam procedures when -pg is on.  I'm suspicious that something similar
> might be going on here.

Yours -> (gcc version 2.95.2 20000220 (Debian GNU/Linux)) 
Mine  -> (gcc version 2.95.4 20010703 (Debian prerelease))
 
> Alternatively, if you have some different versions of gcc lying around,
> you could build UML with them and see if it behaves better.
>
> Also, can you reproduce this with a compiled kernel from the UML site?

I wish I could, but in order to test these lines:

mount -t hostfs none -o /tmp/gboot_non_root_1000/loopback /mnt1
mkfs.jffs2 -r /mnt1/ -o /dev/rd/2
insmod blkmtd.o device=/dev/rd/2
mount -t jffs2 /dev/mtdblock/0 /mnt2

mtd device capability has to be in the kernel, and the same thing applies
in order for jffs/jffs2 to be properly compiled.  Here are the configs
required:

#
# Memory Technology Devices (MTD)
#
CONFIG_MTD=y
CONFIG_MTD_BLKMTD=m
CONFIG_MTD_CHAR=y
CONFIG_MTD_BLOCK=y

Log for failed compile with CONFIG_RWSEM_GENERIC_SPINLOCK replacement:

gcc -D__KERNEL__ -I/usr/src/linux-2.4.17-9um/include -Wall
-Wstrict-prototypes -Wno-trigraphs -O2  -fno-strict-aliasing -fno-common
-fprofile-arcs -ftest-coverage -g -pg -DPROFILING -U__i386__ -Ui386
-D__arch_um__ -DSUBARCH="i386" -DNESTING=0 -D_LARGEFILE64_SOURCE
-I/usr/src/linux-2.4.17-9um/arch/um/include -Derrno=kernel_errno
-DPATCHLEVEL=4    -DEXPORT_SYMTAB -c rwsem-spinlock.c
rwsem-spinlock.c:33: redefinition of `init_rwsem'
/usr/src/linux-2.4.17-9um/include/asm/arch/rwsem.h:85: `init_rwsem'
previously defined here
rwsem-spinlock.c: In function `init_rwsem':
rwsem-spinlock.c:34: structure has no member named `activity'
rwsem-spinlock.c: In function `__rwsem_do_wake':
rwsem-spinlock.c:63: structure has no member named `activity'
rwsem-spinlock.c:82: structure has no member named `activity'
rwsem-spinlock.c: In function `__rwsem_wake_one_writer':
rwsem-spinlock.c:96: structure has no member named `activity'
rwsem-spinlock.c: At top level:
rwsem-spinlock.c:110: redefinition of `__down_read'
/usr/src/linux-2.4.17-9um/include/asm/arch/rwsem.h:98: `__down_read'
previously defined here
rwsem-spinlock.c: In function `__down_read':
rwsem-spinlock.c:118: structure has no member named `activity'
rwsem-spinlock.c:120: structure has no member named `activity'
rwsem-spinlock.c: At top level:
rwsem-spinlock.c:156: redefinition of `__down_write'
/usr/src/linux-2.4.17-9um/include/asm/arch/rwsem.h:123: `__down_write'
previously defined here
rwsem-spinlock.c: In function `__down_write':
rwsem-spinlock.c:164: structure has no member named `activity'
rwsem-spinlock.c:166: structure has no member named `activity'
rwsem-spinlock.c: At top level:
rwsem-spinlock.c:201: redefinition of `__up_read'
/usr/src/linux-2.4.17-9um/include/asm/arch/rwsem.h:150: `__up_read'
previously defined here
rwsem-spinlock.c: In function `__up_read':
rwsem-spinlock.c:206: structure has no member named `activity'
rwsem-spinlock.c: At top level:
rwsem-spinlock.c:218: redefinition of `__up_write'
/usr/src/linux-2.4.17-9um/include/asm/arch/rwsem.h:176: `__up_write'
previously defined here
rwsem-spinlock.c: In function `__up_write':
rwsem-spinlock.c:223: structure has no member named `activity'
make[2]: *** [rwsem-spinlock.o] Error 1
make[2]: Leaving directory `/usr/src/linux-2.4.17-9um/lib'
make[1]: *** [first_rule] Error 2
make[1]: Leaving directory `/usr/src/linux-2.4.17-9um/lib'
make: *** [_dir_lib] Error 2