Instead of having a callback function for each symbol in the kernel,
have a callback for each array of symbols.
This eases the logic when we move to sorted symbols and binary search.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Alessio Igor Bogani <abogani@kernel.org>
Split the unprotect function into a function per section to make
the code more readable and add the missing static declaration.
Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
While debugging I stumbled over two problems in the code that protects module
pages.
First issue is that disabling the protection before freeing init or unload of
a module is not symmetric with the enablement. For instance, if pages are set
to RO the page range from module_core to module_core + core_ro_size is
protected. If a module is unloaded the page range from module_core to
module_core + core_size is set back to RW.
So pages that were not set to RO are also changed to RW.
This is not critical but IMHO it should be symmetric.
Second issue is that while set_memory_rw & set_memory_ro are used for
RO/RW changes only set_memory_nx is involved for NX/X. One would await that
the inverse function is called when the NX protection should be removed,
which is not the case here, unless I'm missing something.
Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reset mod->init_ro_size to zero after the init part of a module is unloaded.
Otherwise we need to check if module->init is NULL in the unprotect functions
in the next patch.
Signed-off-by: Jan Glauber <jang@linux.vnet.ibm.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Fix function prototype to be ANSI-C compliant, consistent with other
function prototypes, addressing a sparse warning.
Signed-off-by: Daniel J Blueman <daniel.blueman@gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reorder structure kparam_array to remove 8 bytes of alignment padding on
64 bit builds, dropping its size from 40 to 32 bytes.
Also update the macro module_param_array_named to initialise the
structure using its member names to allow it to be changed without
touching all its call sites.
'git grep' finds module_param_array in 1037 places so this patch will
save a small amount of data space across many modules.
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Reorder struct module to remove 24 bytes of alignment padding on 64 bit
builds when the CONFIG_TRACE options are selected. This allows the
structure to fit into one fewer cache lines, and its size drops from 592
to 568 on x86_64.
Signed-off-by: Richard Kennedy <richard@rsk.demon.co.uk>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Doing so prevents the following warning from sparse:
CHECK kernel/params.c
kernel/params.c:817:9: warning: symbol '__modver_version_show' was not
declared. Should it be static?
since kernel/params.c is never compiled with MODULE being set.
Signed-off-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
On m68k natural alignment is 2-byte boundary but we are trying to
align structures in __modver section on sizeof(void *) boundary.
This causes trouble when we try to access elements in this section
in array-like fashion when create "version" attributes for built-in
modules.
Moreover, as DaveM said, we can't reliably put structures into
independent objects, put them into a special section, and then expect
array access over them (via the section boundaries) after linking the
objects together to just "work" due to variable alignment choices in
different situations. The only solution that seems to work reliably
is to make an array of plain pointers to the objects in question and
put those pointers in the special section.
Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Dmitry Torokhov <dtor@vmware.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
* 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jlbec/ocfs2:
configfs: Fix race between configfs_readdir() and configfs_d_iput()
configfs: Don't try to d_delete() negative dentries.
ocfs2/dlm: Target node death during resource migration leads to thread spin
ocfs2: Skip mount recovery for hard-ro mounts
ocfs2/cluster: Heartbeat mismatch message improved
ocfs2/cluster: Increase the live threshold for global heartbeat
ocfs2/dlm: Use negotiated o2dlm protocol version
ocfs2: skip existing hole when removing the last extent_rec in punching-hole codes.
ocfs2: Initialize data_ac (might be used uninitialized)
* 'devicetree/merge' of git://git.secretlab.ca/git/linux-2.6:
drivercore: revert addition of of_match to struct device
of: fix race when matching drivers
Commit b826291c, "drivercore/dt: add a match table pointer to struct
device" added an of_match pointer to struct device to cache the
of_match_table entry discovered at driver match time. This was unsafe
because matching is not an atomic operation with probing a driver. If
two or more drivers are attempted to be matched to a driver at the
same time, then the cached matching entry pointer could get
overwritten.
This patch reverts the of_match cache pointer and reworks all users to
call of_match_device() directly instead.
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
If two drivers are probing devices at the same time, both will write
their match table result to the dev->of_match cache at the same time.
Only write the result if the device matches.
In a thread titled "SBus devices sometimes detected, sometimes not",
Meelis reported his SBus hme was not detected about 50% of the time.
From the debug suggested by Grant it was obvious another driver matched
some devices between the call to match the hme and the hme discovery
failling.
Reported-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: Milton Miller <miltonm@bga.com>
[grant.likely: modified to only call of_match_device() once]
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
* 'for-linus' of git://git.kernel.dk/linux-2.6-block:
block: don't delay blk_run_queue_async
scsi: remove performance regression due to async queue run
blk-throttle: Use task_subsys_state() to determine a task's blkio_cgroup
block: rescan partitions on invalidated devices on -ENOMEDIA too
cdrom: always check_disk_change() on open
block: unexport DISK_EVENT_MEDIA_CHANGE for legacy/fringe drivers
The 'size' variable contains the correct register size for both AR7
and Titan, but we never used it to ioremap the correct register size.
This problem only shows up on Titan.
[ralf@linux-mips.org: Fixed the fix. The original patch as in patchwork
recognizes the problem correctly then fails to fix it ...]
Reported-by: Alexander Clouter <alex@digriz.org.uk>
Signed-off-by: Florian Fainelli <florian@openwrt.org>
Patchwork: https://patchwork.linux-mips.org/patch/2380/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This is the MIPS portion of Joe Perches <joe@perches.com>'s
https://patchwork.linux-mips.org/patch/2172/ which seems to have been
lost in time and space.
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
configfs_readdir() will use the existing inode numbers of inodes in the
dcache, but it makes them up for attribute files that aren't currently
instantiated. There is a race where a closing attribute file can be
tearing down at the same time as configfs_readdir() is trying to get its
inode number.
We want to get the inode number of open attribute files, because they
should match while instantiated. We can't lock down the transition
where dentry->d_inode is set to NULL, so we just check for NULL there.
We can, however, ensure that an inode we find isn't iput() in
configfs_d_iput() until after we've accessed it.
Signed-off-by: Joel Becker <jlbec@evilplan.org>
When configfs is faking mkdir() on its subsystem or default group
objects, it starts by adding a negative dentry. It then tries to
instantiate the group. If that should fail, it must clean up after
itself.
I was using d_delete() here, but configfs_attach_group() promises to
return an empty dentry on error. d_delete() explodes with the entry
dentry. Let's try d_drop() instead. The unhashing is what we want for
our dentry.
Signed-off-by: Joel Becker <jlbec@evilplan.org>
Let's check a scenario:
1. blk_delay_queue(q, SCSI_QUEUE_DELAY);
2. blk_run_queue_async();
the second one will became a noop, because q->delay_work already has
WORK_STRUCT_PENDING_BIT set, so the delayed work will still run after
SCSI_QUEUE_DELAY. But blk_run_queue_async actually hopes the delayed
work runs immediately.
Fix this by doing a cancel on potentially pending delayed work
before queuing an immediate run of the workqueue.
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* 'perf-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
perf evlist: Fix per thread mmap setup
perf tools: Honour the cpu list parameter when also monitoring a thread list
kprobes, x86: Disable irqs during optimized callback
* git://git.kernel.org/pub/scm/linux/kernel/git/sfrench/cifs-2.6:
cifs: fix cifsConvertToUCS() for the mapchars case
cifs: add fallback in is_path_accessible for old servers
Provide a stub for proc_mkdir_mode() when CONFIG_PROC_FS is not
enabled, just like the stub for proc_mkdir().
Fixes this linux-next build error:
drivers/net/wireless/airo.c:4504: error: implicit declaration of function 'proc_mkdir_mode'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: "John W. Linville" <linville@tuxdriver.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
os_dump_core() uses abort() to terminate UML in case of an fatal error.
glibc's abort() calls raise(SIGABRT) which makes use of tgkill().
tgkill() has no effect within UML's kernel threads because they are not
pthreads. As fallback abort() executes an invalid instruction to
terminate the process. Therefore UML gets killed by SIGSEGV and leaves a
ugly log entry in the host's kernel ring buffer.
To get rid of this we use our own abort routine.
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
ZONE_CONGESTED should be a state of global memory reclaim. If not, a busy
memcg sets this and give unnecessary throttoling in wait_iff_congested()
against memory recalim in other contexts. This makes system performance
bad.
I'll think about "memcg is congested!" flag is required or not, later.
But this fix is required first.
Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Acked-by: Ying Han <yinghan@google.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Adding the necessary MODULE_DEVICE_TABLE() information allows the driver
to be automatically loaded by udev.
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Cc: Shreshtha Kumar SAHU <shreshthakumar.sahu@stericsson.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Fix switch initialization to ensure that all switches have default routing
disabled. This guarantees that no unexpected RapidIO packets arrive to
the default port set by reset and there is no default routing destination
until it is properly configured by software.
This update also unifies handling of unmapped destinations by tsi57x, IDT
Gen1 and IDT Gen2 switches.
Signed-off-by: Alexandre Bounine <alexandre.bounine@idt.com>
Cc: Kumar Gala <galak@kernel.crashing.org>
Cc: Matt Porter <mporter@kernel.crashing.org>
Cc: Li Yang <leoli@freescale.com>
Cc: Thomas Moll <thomas.moll@sysgo.com>
Cc: <stable@kernel.org> [2.6.37+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
As Metze pointed out, commit 84cdf74e broke mapchars option:
Commit "cifs: fix unaligned accesses in cifsConvertToUCS"
(84cdf74e80) does multiple steps
in just one commit (moving the function and changing it without
testing).
put_unaligned_le16(temp, &target[j]); is never called for any
codepoint the goes via the 'default' switch statement. As a result
we put just zero (or maybe uninitialized) bytes into the target
buffer.
His proposed patch looks correct, but doesn't apply to the current head
of the tree. This patch should also fix it.
Cc: <stable@kernel.org> # .38.x: 581ade4: cifs: clean up various nits in unicode routines (try #2)
Reported-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
The is_path_accessible check uses a QPathInfo call, which isn't
supported by ancient win9x era servers. Fall back to an older
SMBQueryInfo call if it fails with the magic error codes.
Cc: stable@kernel.org
Reported-and-Tested-by: Sandro Bonazzola <sandro.bonazzola@gmail.com>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
Trying to enable the local APIC timer on early K8 revisions
uncovers a number of other issues with it, in conjunction with
the C1E enter path on AMD. Fixing those causes much more churn
and troubles than the benefit of using that timer brings so
don't enable it on K8 at all, falling back to the original
functionality the kernel had wrt to that.
Reported-and-bisected-by: Nick Bowler <nbowler@elliptictech.com>
Cc: Boris Ostrovsky <Boris.Ostrovsky@amd.com>
Cc: Andreas Herrmann <andreas.herrmann3@amd.com>
Cc: Greg Kroah-Hartman <greg@kroah.com>
Cc: Hans Rosenfeld <hans.rosenfeld@amd.com>
Cc: Nick Bowler <nbowler@elliptictech.com>
Cc: Joerg-Volker-Peetz <jvpeetz@web.de>
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Link: http://lkml.kernel.org/r/1305636919-31165-3-git-send-email-bp@amd64.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This reverts commit e20a2d205c, as it crashes
certain boxes with specific AMD CPU models.
Moving the lower endpoint of the Erratum 400 check to accomodate
earlier K8 revisions (A-E) opens a can of worms which is simply
not worth to fix properly by tweaking the errata checking
framework:
* missing IntPenging MSR on revisions < CG cause #GP:
http://marc.info/?l=linux-kernel&m=130541471818831
* makes earlier revisions use the LAPIC timer instead of the C1E
idle routine which switches to HPET, thus not waking up in
deeper C-states:
http://lkml.org/lkml/2011/4/24/20
Therefore, leave the original boundary starting with K8-revF.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Commit c21e6beb removed our queue request_fn re-enter
protection, and defaulted to always running the queues from
kblockd to be safe. This was a known potential slow down,
but should be safe.
Unfortunately this is causing big performance regressions for
some, so we need to improve this logic. Looking into the details
of the re-enter, the real issue is on requeue of requests.
Requeue of requests upon seeing a BUSY condition from the device
ends up re-running the queue, causing traces like this:
scsi_request_fn()
scsi_dispatch_cmd()
scsi_queue_insert()
__scsi_queue_insert()
scsi_run_queue()
scsi_request_fn()
...
potentially causing the issue we want to avoid. So special
case the requeue re-run of the queue, but improve it to offload
the entire run of local queue and starved queue from a single
workqueue callback. This is a lot better than potentially
kicking off a workqueue run for each device seen.
This also fixes the issue of the local device going into recursion,
since the above mentioned commit never moved that queue run out
of line.
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/cjb/mmc:
Revert "mmc: fix a race between card-detect rescan and clock-gate work instances"
Fix new kernel-doc warning in mm/page_alloc.c:
Warning(mm/page_alloc.c:2370): No description found for parameter 'nid'
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
During pci remove/rescan testing found:
pci 0000:c0:03.0: PCI bridge to [bus c4-c9]
pci 0000:c0:03.0: bridge window [io 0x1000-0x0fff]
pci 0000:c0:03.0: bridge window [mem 0xf0000000-0xf00fffff]
pci 0000:c0:03.0: bridge window [mem 0xfc180000000-0xfc197ffffff 64bit pref]
pci 0000:c0:03.0: device not available (can't reserve [io 0x1000-0x0fff])
pci 0000:c0:03.0: Error enabling bridge (-22), continuing
pci 0000:c0:03.0: enabling bus mastering
pci 0000:c0:03.0: setting latency timer to 64
pcieport 0000:c0:03.0: device not available (can't reserve [io 0x1000-0x0fff])
pcieport: probe of 0000:c0:03.0 failed with error -22
This bug was caused by commit c8adf9a3e8 ("PCI: pre-allocate
additional resources to devices only after successful allocation of
essential resources.")
After that commit, pci_hotplug_io_size is changed to additional_io_size
from minium size. So it will not go through resource_size(res) != 0
path, and will not be reset.
The root cause is: pci_bridge_check_ranges will set RESOURCE_IO flag for
pci bridge, and later if children do not need IO resource. those bridge
resources will not need to be allocated. but flags is still there.
that will confuse the the pci_enable_bridges later.
related code:
static void assign_requested_resources_sorted(struct resource_list *head,
struct resource_list_x *fail_head)
{
struct resource *res;
struct resource_list *list;
int idx;
for (list = head->next; list; list = list->next) {
res = list->res;
idx = res - &list->dev->resource[0];
if (resource_size(res) && pci_assign_resource(list->dev, idx)) {
...
reset_resource(res);
}
}
}
At last, We have to clear the flags in pbus_size_mem/io when requested
size == 0 and !add_head. becasue this case it will not go through
adjust_resources_sorted().
Just make size1 = size0 when !add_head. it will make flags get cleared.
At the same time when requested size == 0, add_size != 0, will still
have in head and add_list. because we do not clear the flags for it.
After this, we will get right result:
pci 0000:c0:03.0: PCI bridge to [bus c4-c9]
pci 0000:c0:03.0: bridge window [io disabled]
pci 0000:c0:03.0: bridge window [mem 0xf0000000-0xf00fffff]
pci 0000:c0:03.0: bridge window [mem 0xfc180000000-0xfc197ffffff 64bit pref]
pci 0000:c0:03.0: enabling bus mastering
pci 0000:c0:03.0: setting latency timer to 64
pcieport 0000:c0:03.0: setting latency timer to 64
pcieport 0000:c0:03.0: irq 160 for MSI/MSI-X
pcieport 0000:c0:03.0: Signaling PME through PCIe PME interrupt
pci 0000:c4:00.0: Signaling PME through PCIe PME interrupt
pcie_pme 0000:c0:03.0:pcie01: service driver pcie_pme loaded
aer 0000:c0:03.0:pcie02: service driver aer loaded
pciehp 0000:c0:03.0:pcie04: Hotplug Controller:
v3: more simple fix. also fix one typo in pbus_size_mem
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Reviewed-by: Ram Pai <linuxram@us.ibm.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The first cpu which switches from periodic to oneshot mode switches
also the broadcast device into oneshot mode. The broadcast device
serves as a backup for per cpu timers which stop in deeper
C-states. To avoid starvation of the cpus which might be in idle and
depend on broadcast mode it marks the other cpus as broadcast active
and sets the brodcast expiry value of those cpus to the next tick.
The oneshot mode broadcast bit for the other cpus is sticky and gets
only cleared when those cpus exit idle. If a cpu was not idle while
the bit got set in consequence the bit prevents that the broadcast
device is armed on behalf of that cpu when it enters idle for the
first time after it switched to oneshot mode.
In most cases that goes unnoticed as one of the other cpus has usually
a timer pending which keeps the broadcast device armed with a short
timeout. Now if the only cpu which has a short timer active has the
bit set then the broadcast device will not be armed on behalf of that
cpu and will fire way after the expected timer expiry. In the case of
Christians bug report it took ~145 seconds which is about half of the
wrap around time of HPET (the limit for that device) due to the fact
that all other cpus had no timers armed which expired before the 145
seconds timeframe.
The solution is simply to clear the broadcast active bit
unconditionally when a cpu switches to oneshot mode after the first
cpu switched the broadcast device over. It's not idle at that point
otherwise it would not be executing that code.
[ I fundamentally hate that broadcast crap. Why the heck thought some
folks that when going into deep idle it's a brilliant concept to
switch off the last device which brings the cpu back from that
state? ]
Thanks to Christian for providing all the valuable debug information!
Reported-and-tested-by: Christian Hoffmann <email@christianhoffmann.info>
Cc: John Stultz <johnstul@us.ibm.com>
Link: http://lkml.kernel.org/r/%3Calpine.LFD.2.02.1105161105170.3078%40ionos%3E
Cc: stable@kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Those reduced to DEBUG can possibly be triggered by unprivileged processes
and are nothing exceptional. Illegal checksum combinations can only be
caused by driver bug, so promote those messages to WARN.
Since GSO without SG will now only cause DEBUG message from
netdev_fix_features(), remove the workaround from register_netdevice().
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: David S. Miller <davem@davemloft.net>
During initialization of vmxnet3, the state of LRO
gets out of sync with netdev->features.
This leads to very poor TCP performance in a IP forwarding
setup and is hitting many VMware users.
Simplified call sequence:
1. vmxnet3_declare_features() initializes "adapter->lro" to true.
2. The kernel automatically disables LRO if IP forwarding is enabled,
so vmxnet3_set_flags() gets called. This also updates netdev->features.
3. Now vmxnet3_setup_driver_shared() is called. "adapter->lro" is still
set to true and LRO gets enabled again, even though
netdev->features shows it's disabled.
Fix it by updating "adapter->lro", too.
The private vmxnet3 adapter flags are scheduled for removal
in net-next, see commit a0d2730c95
"net: vmxnet3: convert to hw_features".
Patch applies to 2.6.37 / 2.6.38 and 2.6.39-rc6.
Please CC: comments.
Signed-off-by: Thomas Jarosch <thomas.jarosch@intra2net.com>
Acked-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Commit 747df2258b ('sfc: Always map MCDI
shared memory as uncacheable') introduced a separate mapping for the
MCDI shared memory (MC_TREG_SMEM). This means we can no longer easily
include it in the register dump. Since it is not particularly useful
in debugging, substitute a recognisable dummy value.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
* 'omap-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap-2.6:
OMAP3: set the core dpll clk rate in its set_rate function
omap: iommu: Return IRQ_HANDLED in fault handler when no fault occured
* 'drm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6:
drm: Take lock around probes for drm_fb_helper_hotplug_event
drm/i915: Revert i915.semaphore=1 default from 47ae63e0
vga_switcheroo: don't toggle-switch devices
drm/radeon/kms: add some evergreen/ni safe regs
drm/radeon/kms: fix extended lvds info parsing
drm/radeon/kms: fix tiling reg on fusion
Currentlly we first map the task to cgroup and then cgroup to
blkio_cgroup. There is a more direct way to get to blkio_cgroup
from task using task_subsys_state(). Use that.
The real reason for the fix is that it also avoids a race in generic
cgroup code. During remount/umount rebind_subsystems() is called and
it can do following with and rcu protection.
cgrp->subsys[i] = NULL;
That means if somebody got hold of cgroup under rcu and then it tried
to do cgroup->subsys[] to get to blkio_cgroup, it would get NULL which
is wrong. I was running into this race condition with ltp running on a
upstream derived kernel and that lead to crash.
So ideally we should also fix cgroup generic code to wait for rcu
grace period before setting pointer to NULL. Li Zefan is not very keen
on introducing synchronize_wait() as he thinks it will slow
down moun/remount/umount operations.
So for the time being atleast fix the kernel crash by taking a more
direct route to blkio_cgroup.
One tester had reported a crash while running LTP on a derived kernel
and with this fix crash is no more seen while the test has been
running for over 6 days.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Rusty Russell