perf sched record can deadlock a box should the holder of
handle->data->lock take an interrupt, and then attempt to
acquire an rq lock held by a CPU trying to acquire the
same lock. Disable interrupts.
CPU0 CPU1
sched event with rq->lock held
grab handle->data->lock
spin on handle->data->lock
interrupt
try to grab rq->lock
Reported-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Mike Galbraith <efault@gmx.de>
Tested-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1269598293.6174.8.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
When profiling a 32-bit process on a 64-bit kernel, callgraph tracing
stopped after the first function, because it has seen a garbage memory
address (tried to interpret the frame pointer, and return address as a
64-bit pointer).
Fix this by using a struct stack_frame with 32-bit pointers when the
TIF_IA32 flag is set.
Note that TIF_IA32 flag must be used, and not is_compat_task(), because
the latter is only set when the 32-bit process is executing a syscall,
which may not always be the case (when tracing page fault events for
example).
Signed-off-by: Török Edwin <edwintorok@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: x86@kernel.org
Cc: linux-kernel@vger.kernel.org
LKML-Reference: <1268820436-13145-1-git-send-email-edwintorok@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commit 3f6da39 ("perf: Rework and fix the arch CPU-hotplug hooks") moved
the amd northbridge allocation from CPUS_ONLINE to CPUS_PREPARE_UP
however amd_nb_id() doesn't work yet on prepare so it would simply bail
basically reverting to a state where we do not properly track node wide
constraints - causing weird perf results.
Fix up the AMD NorthBridge initialization code by allocating from
CPU_UP_PREPARE and installing it from CPU_STARTING once we have the
proper nb_id. It also properly deals with the allocation failing.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[ robustify using amd_has_nb() ]
Signed-off-by: Stephane Eranian <eranian@google.com>
LKML-Reference: <1269353485.5109.48.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Because we need to have cpu identification things done by the time we run
CPU_STARTING notifiers.
( This init ordering will be relied on by the next fix. )
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1269353485.5109.48.camel@twins>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Some larger systems require more than 512 nodes, so increase the
maximum CONFIG_NODES_SHIFT to 10 for a new max of 1024 nodes.
This was tested with numa=fake=64M on systems with more than
64GB of RAM. A total of 1022 nodes were initialized.
Successfully builds with no additional warnings on x86_64
allyesconfig.
( No effect on any existing config. Newly enabled CONFIG_MAXSMP=y
will see the new default. )
Signed-off-by: David Rientjes <rientjes@google.com>
LKML-Reference: <alpine.DEB.2.00.1003251538060.8589@chino.kir.corp.google.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
With recent (2.6.34) chnages in PCM handling, capture stopped working on my
OMAP1510 based Amstrad Delta videophone.
Using 2.6.34-rc2, I was able to correct the problem in 3 different ways:
1. reverting commit 7b3a177b0d,
2. enabling additional jiffies check with
echo 4 >/proc/asound/card0/pcm0c0/xrun_debug
3. applying the patch below.
Since I wasn't able to reproduce the problem on my i686 PC, I guess the
problem is probably machine specific.
The patch reuses the method for software emulation of missing hardware
pointer, already implemented for playback on OMAP1510. It's possible that
event if a hardware pointer is available for capture on this machine, its
behaviour may be not compatible with what upper layer expects.
If you think the problem may be more general and should be solved differently,
on a higher level, I can try to work more on it if you give me a hint.
If the patch gets accepted, I suggest it goes as a fix in the current release
cycle.
Created and tested against linux-2.6.34-rc2.
Signed-off-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Acked-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid:
HID: Add NOGET quirk for Quanta Pixart touchscreen
HID: fix oops in gyration_event()
* 'sh/for-2.6.34' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6:
sh: Fix up the SH-3 build for recent TLB changes.
sh: export return_address() symbol.
sh: Enable the mmu in start_secondary()
sh: Fix FDPIC binary loader
arch/sh/kernel: Use set_cpus_allowed_ptr
sh: Update ecovec_defconfig
USB gadget r8a66597-udc.c: duplicated include
sh: update the TLB replacement counter for entry wiring.
`make CONFIG_NILFS2_FS=m M=fs/nilfs2/` will give the following warnings:
fs/nilfs2/btree.c: In function 'nilfs_btree_propagate':
fs/nilfs2/btree.c:1882: warning: 'maxlevel' may be used uninitialized in this function
fs/nilfs2/btree.c:1882: note: 'maxlevel' was declared here
Set maxlevel = 0 to fix it.
Signed-off-by: Li Hong <lihong.hi@gmail.com>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
I hit this when we had a bug in IDR for a few days. Basically sysfs would
fail to create new inodes since it uses an IDR and therefore class_create would
fail.
While we are unlikely to see this fail we may as well handle it instead of
oopsing.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
While the MMUCR.URB and ITLB/UTLB differentiation works fine for all SH-4
and later TLBs, these features are absent on SH-3. This splits out
local_flush_tlb_all() in to SH-4 and PTEAEX copies while restoring the
old SH-3 one, subsequently fixing up the build.
This will probably want some further reordering and tidying in the
future, but that's out of scope at present.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
elevator_get() not check the name length, if the name length > sizeof(elv),
elv will miss the '\0'. And elv buffer will be replace "-iosched" as something
like aaaaaaaaa, then call request_module() can load an not trust module.
Signed-off-by: Zhitong Wang <zhitong.wangzt@alibaba-inc.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
We take the spin_lock again in fail_all_cmds() so we need to unlock
here.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
- Patch adds support to enable PCI SRIOV in the driver and changes to handle initialization of PCI virtual functions.
- Function handler to change mac addresses for VF from its corresponding PF.
Signed-off-by: Sarveshwar Bandi <sarveshwarb@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
BugLink: http://bugs.launchpad.net/bugs/457878
v2:
- remove duplicated phy_speed caculation
- fix the phy_speed caculation according to the DataSheet
v1:
- removed old MII phy control code
- add phylib supporting
- add ethtool interface to make user space NetworkManager works
Tested on Freescale i.MX51 Babbage board.
This patch is based on a patch from Frederic Rodo <fred.rodo@gmail.com>
Cc: Frederic Rodo <fred.rodo@gmail.com>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Acked-by: Amit Kucheria <amit.kucheria@canonical.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Robert Hancock pointed out two problems about NETIF_F_HIGHDMA:
-Many drivers only set the flag when they detect they can use 64-bit DMA,
since otherwise they could receive DMA addresses that they can't handle
(which on platforms without IOMMU/SWIOTLB support is fatal). This means that if
64-bit support isn't available, even buffers located below 4GB will get copied
unnecessarily.
-Some drivers set the flag even though they can't actually handle 64-bit DMA,
which would mean that on platforms without IOMMU/SWIOTLB they would get a DMA
mapping error if the memory they received happened to be located above 4GB.
http://lkml.org/lkml/2010/3/3/530
We can use the dma_mask if we need bouncing or not here. Then we can
safely fix drivers that misuse NETIF_F_HIGHDMA.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>
Adding GRO support on top of the HW LRO (TPA) support –
there is no measurable performance drawback of adding GRO
on top of it, and it allows better performance when LRO (TPA)
is turned off for virtualization or bridging.
Signed-off-by: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Group all per-cpu data to one structure instead of having many
globals. Also prepare the internals so that we can have multiple
instances of the flow cache if needed.
Only the kmem_cache is left as a global as all flow caches share
the same element size, and benefit from using a common cache.
Signed-off-by: Timo Teras <timo.teras@iki.fi>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
All of the code considers ->dead as a hint that the cached policy
needs to get refreshed. The read side can just drop the read lock
without any side effects.
The write side needs to make sure that it's written only exactly
once. Only possible race is at xfrm_policy_kill(). This is fixed
by checking result of __xfrm_policy_unlink() when needed. It will
always succeed if the policy object is looked up from the hash
list (so some checks are removed), but it needs to be checked if
we are trying to unlink policy via a reference (appropriate
checks added).
Since policy->walk.dead is written exactly once, it no longer
needs to be protected with a write lock.
Signed-off-by: Timo Teras <timo.teras@iki.fi>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Add missing check for policy direction verification. This is
especially important since without this xfrm_user may end up
deleting per-socket policy which is not allowed.
Signed-off-by: Timo Teras <timo.teras@iki.fi>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
The xfrm state genid only needs to be matched against the copy
saved in xfrm_dst. So we don't need a global genid at all. In
fact, we don't even need to initialise it.
Based on observation by Timo Teräs.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Fix formatting on r8169 printk
Brandon Philips noted that I had a spacing issue in my printk for the
last r8169 patch that made it quite ugly. Fix that up and add the PFX
macro to it as well so it looks like the other r8169 printks
Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The head element of rt6_info{} is dst_entry{}, and
IPv6 specific elements follow.
Because elements at the end of dst_entry{} are frequently
updated, it is not good to put frequently-used static
elements, such as rt6i_idev, rt6i_dst or rt6i_flags in the
same cache line.
On the other hand, fib6_table, rt6i_node or rt6i_gateway are
rarely used, so it is okay to stay in the same cache line.
Let's rearrange rt6_info{}.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
keep the old behavior on SMP without rps
RPS introduces a lock operation to per cpu variable input_pkt_queue on
SMP whenever rps is enabled or not. On SMP without RPS, this lock isn't
needed at all.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
----
net/core/dev.c | 42 ++++++++++++++++++++++++++++--------------
1 file changed, 28 insertions(+), 14 deletions(-)
Signed-off-by: David S. Miller <davem@davemloft.net>
In case a reset is performed, rtl8169_rx_interrupt() is called from
process context instead of softirq context. Special care must be taken
to call appropriate network core services (netif_rx() instead of
netif_receive_skb()). VLAN handling also corrected.
Reported-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Diagnosed-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
One of my test machine got a deadlock during "tc" sessions,
adding/deleting classes & filters, using traffic estimators.
After some analysis, I believe we have a potential use after free case
in est_timer() :
spin_lock(e->stats_lock); << HERE >>
read_lock(&est_lock);
if (e->bstats == NULL) << TEST >>
goto skip;
Test is done a bit late, because after estimator is killed, and before
rcu grace period elapsed, we might already have freed/reuse memory where
e->stats_locks points to (some qdisc->q.lock)
A possible fix is to respect a rcu grace period at Qdisc dismantle time.
On 64bit, sizeof(struct Qdisc) is exactly 192 bytes. Adding 16 bytes to
it (for struct rcu_head) is a problem because it might change
performance, given QDISC_ALIGNTO is 32 bytes.
This is why I also change QDISC_ALIGNTO to 64 bytes, to satisfy most
current alignment requirements.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
The check if error signaling is wanted (inet->recverr != 0) is done by
the caller: raw.c:raw_err() and udp.c:__udp4_lib_err(), so there is no
need to check this condition again.
Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
acenic wrongly assumes that zero is an invalid dma address (calls
dma_unmap_page for only non zero dma addresses). Zero is a valid dma
address on some architectures. The dma length can be used here.
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>
The recent changes to add RCU lock verification to rcu_dereference() calls
caught out a problem with netlbl_unlhsh_hash(), see below.
===================================================
[ INFO: suspicious rcu_dereference_check() usage. ]
---------------------------------------------------
net/netlabel/netlabel_unlabeled.c:246 invoked rcu_dereference_check()
without protection!
This patch fixes this problem as well as others like it in the NetLabel
code. Also included in this patch is the identification of future work
to eliminate the RCU read lock in netlbl_domhsh_add(), but in the interest
of getting this patch out quickly that work will happen in another patch
to be finished later.
Thanks to Eric Dumazet and Paul McKenney for their help in understanding
the recent RCU changes.
Signed-off-by: Paul Moore <paul.moore@hp.com>
Reported-by: David Howells <dhowells@redhat.com>
CC: Eric Dumazet <eric.dumazet@gmail.com>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
bond_uninit() is invoked with rtnl_lock held, when it does destroy_workqueue()
which will potentially flush all works in this workqueue, if we hold rtnl_lock
again in the work function, it will deadlock.
So move destroy_workqueue() to destructor where rtnl_lock is not held any more,
suggested by Eric.
Signed-off-by: WANG Cong <amwang@redhat.com>
Cc: Jay Vosburgh <fubar@us.ibm.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Stephen Hemminger <shemminger@vyatta.com>
Cc: Jiri Pirko <jpirko@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
check the length of the socket address passed to connect(2).
Check the length of the socket address passed to connect(2). If the
length is invalid, -EINVAL will be returned.
Signed-off-by: Changli Gao <xiaosuo@gmail.com>
----
net/bluetooth/l2cap.c | 3 ++-
net/bluetooth/rfcomm/sock.c | 3 ++-
net/bluetooth/sco.c | 3 ++-
net/can/bcm.c | 3 +++
net/ieee802154/af_ieee802154.c | 3 +++
net/ipv4/af_inet.c | 5 +++++
net/netlink/af_netlink.c | 3 +++
7 files changed, 20 insertions(+), 3 deletions(-)
Signed-off-by: David S. Miller <davem@davemloft.net>
Add Documentation/networking/stmmac.txt for the
stmmac network driver.
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
stmmac uses crc32 functions so it needs to select CRC32.
Fixes build error:
drivers/built-in.o: In function `dwmac1000_set_filter':
dwmac1000_core.c:(.text+0x3c380): undefined reference to `crc32_le'
dwmac1000_core.c:(.text+0x3c384): undefined reference to `bitrev32'
Signed-off-by: Carmelo Amoroso <carmelo.amoroso@st.com>
Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
vlan traffic on big endian architecture is broken.
Need to swap the vid before giving packet to stack.
This patch fixes it.
Signed-off-by: Ajit Khaparde <ajitk@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Flashing is broken on big endian architectures like ppc.
This patch fixes it.
From: Naresh G <nareshg@serverengines.com>
Signed-off-by: Ajit Khaparde <ajitk@serverengines.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This allows arch code could decide the way to reserve the ibft.
And we should reserve ibft as early as possible, instead of BOOTMEM
stage, in case the table is in RAM range and is not reserved by BIOS
(this will often be the case.)
Move to just after find_smp_config().
Also when CONFIG_NO_BOOTMEM=y, We will not have reserve_bootmem() anymore.
-v2: fix typo about ibft pointed by Konrad Rzeszutek Wilk <konrad@darnok.org>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
LKML-Reference: <4BB510FB.80601@kernel.org>
Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Peter Jones <pjones@redhat.com>
Cc: Konrad Rzeszutek Wilk <konrad@kernel.org>
CC: Jan Beulich <jbeulich@novell.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
We think there exists a bug in the HPET code that emulates the RTC.
In the normal case, when the RTC frequency is set, the rtc driver tells
the hpet code about it here:
int hpet_set_periodic_freq(unsigned long freq)
{
uint64_t clc;
if (!is_hpet_enabled())
return 0;
if (freq <= DEFAULT_RTC_INT_FREQ)
hpet_pie_limit = DEFAULT_RTC_INT_FREQ / freq;
else {
clc = (uint64_t) hpet_clockevent.mult * NSEC_PER_SEC;
do_div(clc, freq);
clc >>= hpet_clockevent.shift;
hpet_pie_delta = (unsigned long) clc;
}
return 1;
}
If freq is set to 64Hz (DEFAULT_RTC_INT_FREQ) or lower, then
hpet_pie_limit (a static) is set to non-zero. Then, on every one-shot
HPET interrupt, hpet_rtc_timer_reinit is called to compute the next
timeout. Well, that function has this logic:
if (!(hpet_rtc_flags & RTC_PIE) || hpet_pie_limit)
delta = hpet_default_delta;
else
delta = hpet_pie_delta;
Since hpet_pie_limit is not 0, hpet_default_delta is used. That
corresponds to 64Hz.
Now, if you set a different rtc frequency, you'll take the else path
through hpet_set_periodic_freq, but unfortunately no one resets
hpet_pie_limit back to 0.
Boom....now you are stuck with 64Hz RTC interrupts forever.
The patch below just resets the hpet_pie_limit value when requested freq
is greater than DEFAULT_RTC_INT_FREQ, which we think fixes this problem.
Signed-off-by: Alok N Kataria <akataria@vmware.com>
LKML-Reference: <201003112200.o2BM0Hre012875@imap1.linux-foundation.org>
Signed-off-by: Daniel Hecht <dhecht@vmware.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
On Wed, Feb 24, 2010 at 03:37:04PM -0800, Justin Piszcz wrote:
> Hello,
>
> Again, on the Intel DP55KG board:
>
> # uname -a
> Linux host 2.6.33 #1 SMP Wed Feb 24 18:31:00 EST 2010 x86_64 GNU/Linux
>
> [ 1.237600] ------------[ cut here ]------------
> [ 1.237890] WARNING: at arch/x86/kernel/hpet.c:404 hpet_next_event+0x70/0x80()
> [ 1.238221] Hardware name:
> [ 1.238504] hpet: compare register read back failed.
> [ 1.238793] Modules linked in:
> [ 1.239315] Pid: 0, comm: swapper Not tainted 2.6.33 #1
> [ 1.239605] Call Trace:
> [ 1.239886] <IRQ> [<ffffffff81056c13>] ? warn_slowpath_common+0x73/0xb0
> [ 1.240409] [<ffffffff81079608>] ? tick_dev_program_event+0x38/0xc0
> [ 1.240699] [<ffffffff81056cb0>] ? warn_slowpath_fmt+0x40/0x50
> [ 1.240992] [<ffffffff81079608>] ? tick_dev_program_event+0x38/0xc0
> [ 1.241281] [<ffffffff81041ad0>] ? hpet_next_event+0x70/0x80
> [ 1.241573] [<ffffffff81079608>] ? tick_dev_program_event+0x38/0xc0
> [ 1.241859] [<ffffffff81078e32>] ? tick_handle_oneshot_broadcast+0xe2/0x100
> [ 1.246533] [<ffffffff8102a67a>] ? timer_interrupt+0x1a/0x30
> [ 1.246826] [<ffffffff81085499>] ? handle_IRQ_event+0x39/0xd0
> [ 1.247118] [<ffffffff81087368>] ? handle_edge_irq+0xb8/0x160
> [ 1.247407] [<ffffffff81029f55>] ? handle_irq+0x15/0x20
> [ 1.247689] [<ffffffff810294a2>] ? do_IRQ+0x62/0xe0
> [ 1.247976] [<ffffffff8146be53>] ? ret_from_intr+0x0/0xa
> [ 1.248262] <EOI> [<ffffffff8102f277>] ? mwait_idle+0x57/0x80
> [ 1.248796] [<ffffffff8102645c>] ? cpu_idle+0x5c/0xb0
> [ 1.249080] ---[ end trace db7f668fb6fef4e1 ]---
>
> Is this something Intel has to fix or is it a bug in the kernel?
This is a chipset erratum.
Thomas: You mentioned we can retain this check only for known-buggy and
hpet debug kind of options. But here is the simple workaround patch for
this particular erratum.
Some chipsets have a erratum due to which read immediately following a
write of HPET comparator returns old comparator value instead of most
recently written value.
Erratum 15 in
"Intel I/O Controller Hub 9 (ICH9) Family Specification Update"
(http://www.intel.com/assets/pdf/specupdate/316973.pdf)
Workaround for the errata is to read the comparator twice if the first
one fails.
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
LKML-Reference: <20100225185348.GA9674@linux-os.sc.intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@gmail.com>
Cc: <stable@kernel.org>
