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
..
8253pit.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
a.out-core.h
aout: suppress A.OUT library support if !CONFIG_ARCH_SUPPORTS_AOUT
2008-02-08 09:22:30 -08:00
a.out.h
aout: move STACK_TOP[_MAX] to asm/processor.h
2008-02-08 09:22:29 -08:00
agp.h
x86: remove flush_agp_mappings()
2008-01-30 13:34:07 +01:00
agp_backend.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
atomic.h
alpha: atomic_add_return() should return int
2008-02-05 09:44:21 -08:00
auxvec.h
[PATCH] auxiliary vector cleanups
2005-09-07 16:57:21 -07:00
barrier.h
[PATCH] remove set_wmb - arch removal
2006-07-14 21:56:14 -07:00
bitops.h
forbid asm/bitops.h direct inclusion
2007-10-19 11:53:41 -07:00
bug.h
[PATCH] remove all kernel BUGs
2005-05-01 08:59:01 -07:00
bugs.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
byteorder.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
cache.h
Don't include linux/config.h from anywhere else in include/
2006-04-26 12:56:16 +01:00
cacheflush.h
[PATCH] Optimize D-cache alias handling on fork
2006-12-13 09:27:08 -08:00
checksum.h
[NET]: Alpha checksum annotations and cleanups.
2006-12-02 21:23:01 -08:00
compiler.h
alpha: build fixes - force architecture
2007-04-17 16:36:27 -07:00
console.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
core_apecs.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
core_cia.h
Don't include linux/config.h from anywhere else in include/
2006-04-26 12:56:16 +01:00
core_irongate.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
core_lca.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
core_marvel.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
core_mcpcia.h
alpha: fixes for specific machine types
2007-04-17 16:36:27 -07:00
core_polaris.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
core_t2.h
ALPHA: correct low-level I/O routines for sable-lynx
2007-06-01 08:18:29 -07:00
core_titan.h
ALPHA: support graphics on non-zero PCI domains
2007-06-01 08:18:29 -07:00
core_tsunami.h
ALPHA: support graphics on non-zero PCI domains
2007-06-01 08:18:29 -07:00
core_wildfire.h
ALPHA: misc fixes
2007-06-01 08:18:29 -07:00
cputime.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
current.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
delay.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
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] dma-mapping.h stubs fix
2007-01-30 08:39:21 -08:00
dma.h
Don't include linux/config.h from anywhere else in include/
2006-04-26 12:56:16 +01:00
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
err_common.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
err_ev6.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
err_ev7.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
errno.h
[PATCH] add EOWNERDEAD and ENOTRECOVERABLE version 2
2005-05-01 08:59:06 -07:00
fb.h
fbdev: detect primary display device
2007-07-17 10:23:11 -07:00
fcntl.h
Fix Alpha O_CLOEXEC definition
2007-08-09 08:39:22 -07:00
floppy.h
cleanup floppy.h
2007-10-17 08:42:55 -07:00
fpu.h
[PATCH] bitops: alpha: use config options instead of __alpha_fix__ and __alpha_cix__
2006-03-26 08:57:09 -08:00
futex.h
[PATCH] consolidate asm/futex.h
2006-01-08 20:13:39 -08:00
gct.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
gentrap.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
hardirq.h
Don't include linux/config.h from anywhere else in include/
2006-04-26 12:56:16 +01:00
hw_irq.h
[PATCH] genirq: add ->retrigger() irq op to consolidate hw_irq_resend()
2006-06-29 10:26:23 -07:00
hwrpb.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
ide.h
ide: add CONFIG_IDE_ARCH_OBSOLETE_INIT
2007-10-20 00:32:32 +02:00
io.h
Remove dma_cache_(wback|inv|wback_inv) functions
2007-10-17 08:42:57 -07:00
io_trivial.h
alpha: build fixes
2007-12-17 19:28:16 -08:00
ioctl.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
ioctls.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
ipcbuf.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
irq.h
take declarations of enable_irq() et.al. to linux/interrupt.h
2007-07-22 11:44:00 -07:00
irq_regs.h
[PATCH] minimal alpha pt_regs fixes
2006-10-07 10:51:14 -07:00
jensen.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
Kbuild
[HEADERS] One line per header in Kbuild files to reduce conflicts
2006-09-19 12:43:58 +01:00
kdebug.h
move die notifier handling to common code
2007-05-08 11:15:04 -07:00
kmap_types.h
Don't include linux/config.h from anywhere else in include/
2006-04-26 12:56:16 +01:00
linkage.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
local.h
local_t: alpha extension
2007-05-08 11:15:20 -07:00
machvec.h
[PATCH] alpha pt_regs cleanups: machine_check()
2006-10-08 12:32:36 -07:00
mc146818rtc.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
md.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
mman.h
[PATCH] Remove final references to deprecated "MAP_ANON" page protection flag
2007-02-11 10:51:17 -08:00
mmu.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
mmu_context.h
alpha: fix hard_smp_processor_id compile error
2007-05-15 08:54:00 -07:00
mmzone.h
[PATCH] Standardize pxx_page macros
2006-09-26 08:48:51 -07:00
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
pal.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
param.h
avoid overflows in kernel/time.c
2008-02-08 09:22:39 -08:00
parport.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
pci.h
iommu sg merging: alpha: make pci_iommu respect the segment size limits
2008-02-05 09:44:10 -08:00
percpu.h
[PATCH] x86-64: Account for module percpu space separately from kernel percpu
2007-05-02 19:27:11 +02:00
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
[PATCH] FD_ZERO build fix
2007-01-11 18:18:22 -08:00
processor.h
aout: move STACK_TOP[_MAX] to asm/processor.h
2008-02-08 09:22:29 -08:00
ptrace.h
alpha: convert to generic sys_ptrace
2007-10-16 09:43:03 -07:00
reg.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
regdef.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
resource.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
rtc.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
rwsem.h
[PATCH] lockdep: remove RWSEM_DEBUG remnants
2006-07-03 15:27:01 -07:00
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.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
serial.h
Don't include linux/config.h from anywhere else in include/
2006-04-26 12:56:16 +01:00
setup.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
sfp-machine.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
[PATCH] consolidate SIGEV_PAD_SIZE
2005-05-01 08:59:08 -07:00
signal.h
[PATCH] irq-flags: ALPHA: Use the new IRQF_ constants
2006-07-02 13:58:46 -07:00
smp.h
Remove hardcoding of hard_smp_processor_id on UP systems
2007-05-09 12:30:48 -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] Directed yield: cpu_relax variants for spinlocks and rw-locks
2006-10-01 00:39:21 -07:00
spinlock_types.h
[PATCH] spinlock consolidation
2005-09-10 10:06:21 -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
[STRING]: Move strcasecmp/strncasecmp to lib/string.c
2007-04-26 01:54:39 -07:00
suspend.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
sysinfo.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
system.h
Add cmpxchg64 and cmpxchg64_local to alpha
2008-02-07 08:42:30 -08:00
termbits.h
[PATCH] tty: preparatory structures for termios revamp
2006-12-08 08:28:56 -08:00
termios.h
alpha termios.h hadn't been updated
2007-07-17 11:01:07 -07:00
thread_info.h
remove unused TIF_NOTIFY_RESUME flag
2007-07-31 15:39:38 -07:00
timex.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00
tlb.h
add mm argument to pte/pmd/pud/pgd_free
2008-02-05 09:44:18 -08:00
tlbflush.h
alpha: fix warning by fixing flush_tlb_kernel_range()
2008-02-05 09:44:22 -08:00
topology.h
[PATCH] more for_each_cpu() conversions
2006-03-23 07:38:17 -08:00
types.h
[PATCH] sab: consolidate kmem_bufctl_t
2005-09-05 00:05:48 -07:00
uaccess.h
[PATCH] remove verify_area(): remove verify_area() from various uaccess.h headers
2005-09-07 16:57:35 -07:00
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
Alpha doesn't use socketcall
2008-02-05 09:44:21 -08:00
user.h
Sanitize the type of struct user.u_ar0
2008-02-07 08:42:30 -08:00
vga.h
ALPHA: support graphics on non-zero PCI domains
2007-06-01 08:18:29 -07:00
xor.h
Linux-2.6.12-rc2
2005-04-16 15:20:36 -07:00