alistair23-linux/include/asm-cris
H. Peter Anvin bdc807871d avoid overflows in kernel/time.c
When the conversion factor between jiffies and milli- or microseconds is
not a single multiply or divide, as for the case of HZ == 300, we currently
do a multiply followed by a divide.  The intervening result, however, is
subject to overflows, especially since the fraction is not simplified (for
HZ == 300, we multiply by 300 and divide by 1000).

This is exposed to the user when passing a large timeout to poll(), for
example.

This patch replaces the multiply-divide with a reciprocal multiplication on
32-bit platforms.  When the input is an unsigned long, there is no portable
way to do this on 64-bit platforms there is no portable way to do this
since it requires a 128-bit intermediate result (which gcc does support on
64-bit platforms but may generate libgcc calls, e.g.  on 64-bit s390), but
since the output is a 32-bit integer in the cases affected, just simplify
the multiply-divide (*3/10 instead of *300/1000).

The reciprocal multiply used can have off-by-one errors in the upper half
of the valid output range.  This could be avoided at the expense of having
to deal with a potential 65-bit intermediate result.  Since the intent is
to avoid overflow problems and most of the other time conversions are only
semiexact, the off-by-one errors were considered an acceptable tradeoff.

At Ralf Baechle's suggestion, this version uses a Perl script to compute
the necessary constants.  We already have dependencies on Perl for kernel
compiles.  This does, however, require the Perl module Math::BigInt, which
is included in the standard Perl distribution starting with version 5.8.0.
In order to support older versions of Perl, include a table of canned
constants in the script itself, and structure the script so that
Math::BigInt isn't required if pulling values from said table.

Running the script requires that the HZ value is available from the
Makefile.  Thus, this patch also adds the Kconfig variable CONFIG_HZ to the
architectures which didn't already have it (alpha, cris, frv, h8300, m32r,
m68k, m68knommu, sparc, v850, and xtensa.) It does *not* touch the sh or
sh64 architectures, since Paul Mundt has dealt with those separately in the
sh tree.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Ralf Baechle <ralf@linux-mips.org>,
Cc: Sam Ravnborg <sam@ravnborg.org>,
Cc: Paul Mundt <lethal@linux-sh.org>,
Cc: Richard Henderson <rth@twiddle.net>,
Cc: Michael Starvik <starvik@axis.com>,
Cc: David Howells <dhowells@redhat.com>,
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>,
Cc: Hirokazu Takata <takata@linux-m32r.org>,
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
Cc: Roman Zippel <zippel@linux-m68k.org>,
Cc: William L. Irwin <sparclinux@vger.kernel.org>,
Cc: Chris Zankel <chris@zankel.net>,
Cc: H. Peter Anvin <hpa@zytor.com>,
Cc: Jan Engelhardt <jengelh@computergmbh.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 09:22:39 -08:00
..
arch-v10 ide: remove stale ide.h "configuration options" 2008-01-25 22:17:08 +01:00
arch-v32 ide: remove stale ide.h "configuration options" 2008-01-25 22:17:08 +01:00
a.out.h aout: move STACK_TOP[_MAX] to asm/processor.h 2008-02-08 09:22:29 -08:00
atomic.h cris-build-fixes-atomich-needs-compilerh-fix 2007-11-14 18:45:45 -08:00
auxvec.h [PATCH] auxiliary vector cleanups 2005-09-07 16:57:21 -07:00
axisflashmap.h [PATCH] CRIS update: misc patches 2005-07-27 16:26:00 -07:00
bitops.h cris: remove unused __dummy, CONST_ADDR and ADDR from bitops.h 2008-02-05 09:44:24 -08:00
bug.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
bugs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
byteorder.h Clean up exported headers on CRIS 2006-09-21 09:33:55 +01:00
cache.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
cacheflush.h [PATCH] Optimize D-cache alias handling on fork 2006-12-13 09:27:08 -08:00
checksum.h cris build fixes: fix csum_tcpudp_magic() declaration 2007-11-14 18:45:44 -08:00
cputime.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
current.h [PATCH] cris: "extern inline" -> "static inline" 2005-11-07 07:53:30 -08:00
delay.h [PATCH] cris: "extern inline" -> "static inline" 2005-11-07 07:53:30 -08:00
device.h Driver core: add dev_archdata to struct device 2006-12-01 14:52:01 -08:00
div64.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
dma-mapping.h [PATCH] Pass struct dev pointer to dma_cache_sync() 2006-12-07 08:39:41 -08:00
dma.h [PATCH] CRIS update: pci 2005-07-27 16:26:00 -07:00
elf.h Cleanup asm/{elf,page,user}.h: #ifdef __KERNEL__ is no longer needed 2008-02-07 08:42:30 -08:00
emergency-restart.h [PATCH] Add emergency_restart() 2005-07-26 14:35:41 -07:00
errno.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
eshlibld.h Don't include linux/config.h from anywhere else in include/ 2006-04-26 12:56:16 +01:00
ethernet.h cris build fixes: update eth_v10.c ethernet driver 2007-11-14 18:45:45 -08:00
etraxgpio.h Don't include linux/config.h from anywhere else in include/ 2006-04-26 12:56:16 +01:00
etraxi2c.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
fasttimer.h CRISv10 improve and bugfix fasttimer 2007-11-14 18:45:47 -08:00
fb.h fbdev: detect primary display device 2007-07-17 10:23:11 -07:00
fcntl.h [PATCH] Clean up struct flock64 definitions 2005-09-07 16:57:38 -07:00
futex.h [PATCH] consolidate asm/futex.h 2006-01-08 20:13:39 -08:00
hardirq.h cris build fixes: hardirq.h: include asm/irq.h 2007-11-14 18:45:45 -08:00
hw_irq.h [PATCH] genirq: add ->retrigger() irq op to consolidate hw_irq_resend() 2006-06-29 10:26:23 -07:00
ide.h [PATCH] CRIS update: drivers 2005-07-27 16:25:59 -07:00
io.h [PATCH] kill eth_io_copy_and_sum() 2007-02-09 09:14:07 -08:00
ioctl.h [PATCH] Generic ioctl.h 2006-01-10 08:01:34 -08:00
ioctls.h etrax: enable arbitary speed setting on tty ports 2007-07-16 09:05:38 -07:00
ipcbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
irq.h [PATCH] genirq: cleanup: turn ARCH_HAS_IRQ_PER_CPU into CONFIG_IRQ_PER_CPU 2006-06-29 10:26:23 -07:00
irq_regs.h softlockup: make asm/irq_regs.h available on every platform 2007-10-17 08:42:47 -07:00
Kbuild Clean up exported headers on CRIS 2006-09-21 09:33:55 +01:00
kdebug.h move die notifier handling to common code 2007-05-08 11:15:04 -07:00
kmap_types.h [PATCH] CRIS update: updates for 2.6.12 2005-07-27 16:26:01 -07:00
linkage.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
local.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mman.h [PATCH] add asm-generic/mman.h 2006-02-15 15:32:22 -08:00
mmu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mmu_context.h [PATCH] x86: PARAVIRT: add hooks to intercept mm creation and destruction 2007-05-02 19:27:14 +02:00
module.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
msgbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
mutex.h [PATCH] mutex subsystem, add default include/asm-*/mutex.h files 2006-01-09 15:59:19 -08:00
namei.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
page.h Cleanup asm/{elf,page,user}.h: #ifdef __KERNEL__ is no longer needed 2008-02-07 08:42:30 -08:00
param.h avoid overflows in kernel/time.c 2008-02-08 09:22:39 -08:00
pci.h PCI: remove pci_dac_dma_... APIs 2007-07-11 16:02:11 -07:00
percpu.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
pgalloc.h add mm argument to pte/pmd/pud/pgd_free 2008-02-05 09:44:18 -08:00
pgtable.h page table handling cleanup 2007-07-16 09:05:36 -07:00
poll.h Consolidate asm/poll.h 2007-05-11 08:29:34 -07:00
posix_types.h asm-*/posix_types.h: scrub __GLIBC__ 2008-02-08 09:22:34 -08:00
processor.h aout: move STACK_TOP[_MAX] to asm/processor.h 2008-02-08 09:22:29 -08:00
ptrace.h [PATCH] CRIS update: profiler 2005-07-27 16:26:00 -07:00
resource.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
rs485.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
rtc.h Don't include linux/config.h from anywhere else in include/ 2006-04-26 12:56:16 +01:00
scatterlist.h Add CONFIG_DEBUG_SG sg validation 2007-10-22 21:20:03 +02:00
sections.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
segment.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
semaphore-helper.h [PATCH] CRIS: turn local_save_flags() + local_irq_disable() into local_irq_save() in headers 2007-02-11 10:51:20 -08:00
semaphore.h kill DECLARE_MUTEX_LOCKED 2007-10-17 08:42:47 -07:00
sembuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
setup.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
shmbuf.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
shmparam.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sigcontext.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
siginfo.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
signal.h [PATCH] irq-flags: CRIS: Use the new IRQF_ constants 2006-07-02 13:58:46 -07:00
smp.h [PATCH] CRIS update: SMP 2005-07-27 16:26:01 -07:00
socket.h [NET]: Introducing socket mark socket option. 2008-01-31 19:27:19 -08:00
sockios.h [NET]: Introduce SIOCGSTAMPNS ioctl to get timestamps with nanosec resolution 2007-04-25 22:24:04 -07:00
spinlock.h [PATCH] CRIS update: SMP 2005-07-27 16:26:01 -07:00
stat.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
statfs.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
string.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
sync_serial.h [PATCH] CRIS update: synchronous serial port driver 2005-07-27 16:26:01 -07:00
system.h Add cmpxchg_local to cris 2008-02-07 08:42:31 -08:00
termbits.h cris build fixes: add baud rate defines 2007-11-14 18:45:45 -08:00
termios.h etrax: enable arbitary speed setting on tty ports 2007-07-16 09:05:38 -07:00
thread_info.h cris build fixes: corrected and improved NMI and IRQ handling 2007-11-14 18:45:45 -08:00
timex.h [PATCH] cris: "extern inline" -> "static inline" 2005-11-07 07:53:30 -08:00
tlb.h CRIS tlb.h should include linux/pagemap.h 2007-11-14 18:45:47 -08:00
tlbflush.h remove unused flush_tlb_pgtables 2007-10-19 11:53:34 -07:00
topology.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
types.h remove strict ansi check from __u64 in asm/types.h 2007-10-17 08:42:53 -07:00
uaccess.h [PATCH] cris: "extern inline" -> "static inline" 2005-11-07 07:53:30 -08:00
ucontext.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
unaligned.h Linux-2.6.12-rc2 2005-04-16 15:20:36 -07:00
unistd.h CRIS: define __ARCH_WANT_SYS_RT_SIGSUSPEND in unistd.h for CRIS 2008-01-14 08:52:23 -08:00
user.h Sanitize the type of struct user.u_ar0 2008-02-07 08:42:30 -08:00