When ran from the sched-out path (preempt_notifier or perf_event),
p->state is irrelevant to determine preemption. You can get preempted
with !task_is_running() just fine.
The right indicator for preemption is if the task is still on the
runqueue in the sched-out path.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20210611082838.285099381@infradead.org
Remove broken task->state references and let wake_up_process() DTRT.
The anti-pattern in these patches breaks the ordering of ->state vs
COND as described in the comment near set_current_state() and can lead
to missed wakeups:
(OoO load, observes RUNNING)<-.
for (;;) { |
t->state = UNINTERRUPTIBLE; |
smp_mb(); ,-----> | (observes !COND)
| /
if (COND) ---------' | COND = 1;
break; `- if (t->state != RUNNING)
wake_up_process(t); // not done
schedule(); // forever waiting
}
t->state = TASK_RUNNING;
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.160855222@infradead.org
This commit in sched/urgent moved the cfs_rq_is_decayed() function:
a7b359fc6a: ("sched/fair: Correctly insert cfs_rq's to list on unthrottle")
and this fresh commit in sched/core modified it in the old location:
9e077b52d8: ("sched/pelt: Check that *_avg are null when *_sum are")
Merge the two variants.
Conflicts:
kernel/sched/fair.c
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This is a partial forward-port of Peter Ziljstra's work first posted
at:
https://lore.kernel.org/lkml/20180530142236.667774973@infradead.org/
Currently select_idle_cpu()'s proportional scheme uses the average idle
time *for when we are idle*, that is temporally challenged. When a CPU
is not at all idle, we'll happily continue using whatever value we did
see when the CPU goes idle. To fix this, introduce a separate average
idle and age it (the existing value still makes sense for things like
new-idle balancing, which happens when we do go idle).
The overall goal is to not spend more time scanning for idle CPUs than
we're idle for. Otherwise we're inhibiting work. This means that we need to
consider the cost over all the wake-ups between consecutive idle periods.
To track this, the scan cost is subtracted from the estimated average
idle time.
The impact of this patch is related to workloads that have domains that
are fully busy or overloaded. Without the patch, the scan depth may be
too high because a CPU is not reaching idle.
Due to the nature of the patch, this is a regression magnet. It
potentially wins when domains are almost fully busy or overloaded --
at that point searches are likely to fail but idle is not being aged
as CPUs are active so search depth is too large and useless. It will
potentially show regressions when there are idle CPUs and a deep search is
beneficial. This tbench result on a 2-socket broadwell machine partially
illustates the problem
5.13.0-rc2 5.13.0-rc2
vanilla sched-avgidle-v1r5
Hmean 1 445.02 ( 0.00%) 451.36 * 1.42%*
Hmean 2 830.69 ( 0.00%) 846.03 * 1.85%*
Hmean 4 1350.80 ( 0.00%) 1505.56 * 11.46%*
Hmean 8 2888.88 ( 0.00%) 2586.40 * -10.47%*
Hmean 16 5248.18 ( 0.00%) 5305.26 * 1.09%*
Hmean 32 8914.03 ( 0.00%) 9191.35 * 3.11%*
Hmean 64 10663.10 ( 0.00%) 10192.65 * -4.41%*
Hmean 128 18043.89 ( 0.00%) 18478.92 * 2.41%*
Hmean 256 16530.89 ( 0.00%) 17637.16 * 6.69%*
Hmean 320 16451.13 ( 0.00%) 17270.97 * 4.98%*
Note that 8 was a regression point where a deeper search would have helped
but it gains for high thread counts when searches are useless. Hackbench
is a more extreme example although not perfect as the tasks idle rapidly
hackbench-process-pipes
5.13.0-rc2 5.13.0-rc2
vanilla sched-avgidle-v1r5
Amean 1 0.3950 ( 0.00%) 0.3887 ( 1.60%)
Amean 4 0.9450 ( 0.00%) 0.9677 ( -2.40%)
Amean 7 1.4737 ( 0.00%) 1.4890 ( -1.04%)
Amean 12 2.3507 ( 0.00%) 2.3360 * 0.62%*
Amean 21 4.0807 ( 0.00%) 4.0993 * -0.46%*
Amean 30 5.6820 ( 0.00%) 5.7510 * -1.21%*
Amean 48 8.7913 ( 0.00%) 8.7383 ( 0.60%)
Amean 79 14.3880 ( 0.00%) 13.9343 * 3.15%*
Amean 110 21.2233 ( 0.00%) 19.4263 * 8.47%*
Amean 141 28.2930 ( 0.00%) 25.1003 * 11.28%*
Amean 172 34.7570 ( 0.00%) 30.7527 * 11.52%*
Amean 203 41.0083 ( 0.00%) 36.4267 * 11.17%*
Amean 234 47.7133 ( 0.00%) 42.0623 * 11.84%*
Amean 265 53.0353 ( 0.00%) 47.7720 * 9.92%*
Amean 296 60.0170 ( 0.00%) 53.4273 * 10.98%*
Stddev 1 0.0052 ( 0.00%) 0.0025 ( 51.57%)
Stddev 4 0.0357 ( 0.00%) 0.0370 ( -3.75%)
Stddev 7 0.0190 ( 0.00%) 0.0298 ( -56.64%)
Stddev 12 0.0064 ( 0.00%) 0.0095 ( -48.38%)
Stddev 21 0.0065 ( 0.00%) 0.0097 ( -49.28%)
Stddev 30 0.0185 ( 0.00%) 0.0295 ( -59.54%)
Stddev 48 0.0559 ( 0.00%) 0.0168 ( 69.92%)
Stddev 79 0.1559 ( 0.00%) 0.0278 ( 82.17%)
Stddev 110 1.1728 ( 0.00%) 0.0532 ( 95.47%)
Stddev 141 0.7867 ( 0.00%) 0.0968 ( 87.69%)
Stddev 172 1.0255 ( 0.00%) 0.0420 ( 95.91%)
Stddev 203 0.8106 ( 0.00%) 0.1384 ( 82.92%)
Stddev 234 1.1949 ( 0.00%) 0.1328 ( 88.89%)
Stddev 265 0.9231 ( 0.00%) 0.0820 ( 91.11%)
Stddev 296 1.0456 ( 0.00%) 0.1327 ( 87.31%)
Again, higher thread counts benefit and the standard deviation
shows that results are also a lot more stable when the idle
time is aged.
The patch potentially matters when a socket was multiple LLCs as the
maximum search depth is lower. However, some of the test results were
suspiciously good (e.g. specjbb2005 gaining 50% on a Zen1 machine) and
other results were not dramatically different to other mcahines.
Given the nature of the patch, Peter's full series is not being forward
ported as each part should stand on its own. Preferably they would be
merged at different times to reduce the risk of false bisections.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20210615111611.GH30378@techsingularity.net
Energy Aware Scheduling (EAS) needs to predict the decisions made by
SchedUtil. The map_util_freq() exists to do that.
There are corner cases where the max allowed frequency might be reduced
(due to thermal). SchedUtil as a CPUFreq governor, is aware of that
but EAS is not. This patch aims to address it.
SchedUtil stores the maximum allowed frequency in
'sugov_policy::next_freq' field. EAS has to predict that value, which is
the real used frequency. That value is made after a call to
cpufreq_driver_resolve_freq() which clamps to the CPUFreq policy limits.
In the existing code EAS is not able to predict that real frequency.
This leads to energy estimation errors.
To avoid wrong energy estimation in EAS (due to frequency miss prediction)
make sure that the step which calculates Performance Domain frequency,
is also aware of the allowed CPU capacity.
Furthermore, modify map_util_freq() to not extend the frequency value.
Instead, use map_util_perf() to extend the util value in both places:
SchedUtil and EAS, but for EAS clamp it to max allowed CPU capacity.
In the end, we achieve the same desirable behavior for both subsystems
and alignment in regards to the real CPU frequency.
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> (For the schedutil part)
Link: https://lore.kernel.org/r/20210614191238.23224-1-lukasz.luba@arm.com
Energy Aware Scheduling (EAS) needs to be able to predict the frequency
requests made by the SchedUtil governor to properly estimate energy used
in the future. It has to take into account CPUs utilization and forecast
Performance Domain (PD) frequency. There is a corner case when the max
allowed frequency might be reduced due to thermal. SchedUtil is aware of
that reduced frequency, so it should be taken into account also in EAS
estimations.
SchedUtil, as a CPUFreq governor, knows the maximum allowed frequency of
a CPU, thanks to cpufreq_driver_resolve_freq() and internal clamping
to 'policy::max'. SchedUtil is responsible to respect that upper limit
while setting the frequency through CPUFreq drivers. This effective
frequency is stored internally in 'sugov_policy::next_freq' and EAS has
to predict that value.
In the existing code the raw value of arch_scale_cpu_capacity() is used
for clamping the returned CPU utilization from effective_cpu_util().
This patch fixes issue with too big single CPU utilization, by introducing
clamping to the allowed CPU capacity. The allowed CPU capacity is a CPU
capacity reduced by thermal pressure raw value.
Thanks to knowledge about allowed CPU capacity, we don't get too big value
for a single CPU utilization, which is then added to the util sum. The
util sum is used as a source of information for estimating whole PD energy.
To avoid wrong energy estimation in EAS (due to capped frequency), make
sure that the calculation of util sum is aware of allowed CPU capacity.
This thermal pressure might be visible in scenarios where the CPUs are not
heavily loaded, but some other component (like GPU) drastically reduced
available power budget and increased the SoC temperature. Thus, we still
use EAS for task placement and CPUs are not over-utilized.
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20210614191128.22735-1-lukasz.luba@arm.com
The thermal pressure signal gives information to the scheduler about
reduced CPU capacity due to thermal. It is based on a value stored in
a per-cpu 'thermal_pressure' variable. The online CPUs will get the
new value there, while the offline won't. Unfortunately, when the CPU
is back online, the value read from per-cpu variable might be wrong
(stale data). This might affect the scheduler decisions, since it
sees the CPU capacity differently than what is actually available.
Fix it by making sure that all online+offline CPUs would get the
proper value in their per-cpu variable when thermal framework sets
capping.
Fixes: f12e4f66ab ("thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping")
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Link: https://lore.kernel.org/r/20210614191030.22241-1-lukasz.luba@arm.com
Fix an issue where fairness is decreased since cfs_rq's can end up not
being decayed properly. For two sibling control groups with the same
priority, this can often lead to a load ratio of 99/1 (!!).
This happens because when a cfs_rq is throttled, all the descendant
cfs_rq's will be removed from the leaf list. When they initial cfs_rq
is unthrottled, it will currently only re add descendant cfs_rq's if
they have one or more entities enqueued. This is not a perfect
heuristic.
Instead, we insert all cfs_rq's that contain one or more enqueued
entities, or it its load is not completely decayed.
Can often lead to situations like this for equally weighted control
groups:
$ ps u -C stress
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND
root 10009 88.8 0.0 3676 100 pts/1 R+ 11:04 0:13 stress --cpu 1
root 10023 3.0 0.0 3676 104 pts/1 R+ 11:04 0:00 stress --cpu 1
Fixes: 31bc6aeaab ("sched/fair: Optimize update_blocked_averages()")
[vingo: !SMP build fix]
Signed-off-by: Odin Ugedal <odin@uged.al>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://lore.kernel.org/r/20210612112815.61678-1-odin@uged.al
Pull perf tools fixes from Arnaldo Carvalho de Melo:
- Correct buffer copying when peeking events
- Sync cpufeatures/disabled-features.h header with the kernel sources
* tag 'perf-tools-fixes-for-v5.13-2021-06-13' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux:
tools headers cpufeatures: Sync with the kernel sources
perf session: Correct buffer copying when peeking events
Pull NFS client bugfixes from Trond Myklebust:
"Highlights include:
Stable fixes:
- Fix use-after-free in nfs4_init_client()
Bugfixes:
- Fix deadlock between nfs4_evict_inode() and nfs4_opendata_get_inode()
- Fix second deadlock in nfs4_evict_inode()
- nfs4_proc_set_acl should not change the value of NFS_CAP_UIDGID_NOMAP
- Fix setting of the NFS_CAP_SECURITY_LABEL capability"
* tag 'nfs-for-5.13-3' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
NFSv4: Fix second deadlock in nfs4_evict_inode()
NFSv4: Fix deadlock between nfs4_evict_inode() and nfs4_opendata_get_inode()
NFS: FMODE_READ and friends are C macros, not enum types
NFS: Fix a potential NULL dereference in nfs_get_client()
NFS: Fix use-after-free in nfs4_init_client()
NFS: Ensure the NFS_CAP_SECURITY_LABEL capability is set when appropriate
NFSv4: nfs4_proc_set_acl needs to restore NFS_CAP_UIDGID_NOMAP on error.
Pull SCSI fixes from James Bottomley:
"Four reasonably small fixes to the core for scsi host allocation
failure paths.
The root problem is that we're not freeing the memory allocated by
dev_set_name(), which involves a rejig of may of the free on error
paths to do put_device() instead of kfree which, in turn, has several
other knock on ramifications and inspection turned up a few other
lurking bugs"
* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
scsi: core: Only put parent device if host state differs from SHOST_CREATED
scsi: core: Put .shost_dev in failure path if host state changes to RUNNING
scsi: core: Fix failure handling of scsi_add_host_with_dma()
scsi: core: Fix error handling of scsi_host_alloc()
Pull RISC-V fixes from Palmer Dabbelt:
- A pair of XIP fixes: one to fix alternatives, and one to turn off the
rest of the features that require code modification
- A fix to a type that was causing some alternatives to break
- A build fix for BUILTIN_DTB
* tag 'riscv-for-linus-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
riscv: Fix BUILTIN_DTB for sifive and microchip soc
riscv: alternative: fix typo in macro name
riscv: code patching only works on !XIP_KERNEL
riscv: xip: support runtime trap patching
0day robot reported a 9.2% regression for will-it-scale mmap1 test
case[1], caused by commit 57efa1fe59 ("mm/gup: prevent gup_fast from
racing with COW during fork").
Further debug shows the regression is due to that commit changes the
offset of hot fields 'mmap_lock' inside structure 'mm_struct', thus some
cache alignment changes.
From the perf data, the contention for 'mmap_lock' is very severe and
takes around 95% cpu cycles, and it is a rw_semaphore
struct rw_semaphore {
atomic_long_t count; /* 8 bytes */
atomic_long_t owner; /* 8 bytes */
struct optimistic_spin_queue osq; /* spinner MCS lock */
...
Before commit 57efa1fe59 adds the 'write_protect_seq', it happens to
have a very optimal cache alignment layout, as Linus explained:
"and before the addition of the 'write_protect_seq' field, the
mmap_sem was at offset 120 in 'struct mm_struct'.
Which meant that count and owner were in two different cachelines,
and then when you have contention and spend time in
rwsem_down_write_slowpath(), this is probably *exactly* the kind
of layout you want.
Because first the rwsem_write_trylock() will do a cmpxchg on the
first cacheline (for the optimistic fast-path), and then in the
case of contention, rwsem_down_write_slowpath() will just access
the second cacheline.
Which is probably just optimal for a load that spends a lot of
time contended - new waiters touch that first cacheline, and then
they queue themselves up on the second cacheline."
After the commit, the rw_semaphore is at offset 128, which means the
'count' and 'owner' fields are now in the same cacheline, and causes
more cache bouncing.
Currently there are 3 "#ifdef CONFIG_XXX" before 'mmap_lock' which will
affect its offset:
CONFIG_MMU
CONFIG_MEMBARRIER
CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES
The layout above is on 64 bits system with 0day's default kernel config
(similar to RHEL-8.3's config), in which all these 3 options are 'y'.
And the layout can vary with different kernel configs.
Relayouting a structure is usually a double-edged sword, as sometimes it
can helps one case, but hurt other cases. For this case, one solution
is, as the newly added 'write_protect_seq' is a 4 bytes long seqcount_t
(when CONFIG_DEBUG_LOCK_ALLOC=n), placing it into an existing 4 bytes
hole in 'mm_struct' will not change other fields' alignment, while
restoring the regression.
Link: https://lore.kernel.org/lkml/20210525031636.GB7744@xsang-OptiPlex-9020/ [1]
Reported-by: kernel test robot <oliver.sang@intel.com>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Pull USB fixes from Greg KH:
"Here are a number of tiny USB fixes for 5.13-rc6.
There are more than I would normally like, but there's been a bunch of
people banging on the gadget and dwc3 and typec code recently for I
think an Android release, which has resulted in a number of small
fixes. It's nice to see companies send fixes upstream for this type of
work, a notable change from years ago.
Anyway, fixes in here are:
- usb-serial device id updates
- usb-serial cp210x driver fixes for broken firmware versions
- typec fixes for crazy charging devices and other reported problems
- dwc3 fixes for reported problems found
- gadget fixes for reported problems
- tiny xhci fixes
- other small fixes for reported issues.
- revert of a problem fix found by linux-next testing
All of these have passed 0-day and linux-next testing with no reported
problems (the revert for the found linux-next build problem included)"
* tag 'usb-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb: (44 commits)
Revert "usb: gadget: fsl: Re-enable driver for ARM SoCs"
usb: typec: mux: Fix copy-paste mistake in typec_mux_match
usb: typec: ucsi: Clear PPM capability data in ucsi_init() error path
usb: gadget: fsl: Re-enable driver for ARM SoCs
usb: typec: wcove: Use LE to CPU conversion when accessing msg->header
USB: serial: cp210x: fix CP2102N-A01 modem control
USB: serial: cp210x: fix alternate function for CP2102N QFN20
usb: misc: brcmstb-usb-pinmap: check return value after calling platform_get_resource()
usb: dwc3: ep0: fix NULL pointer exception
usb: gadget: eem: fix wrong eem header operation
usb: typec: intel_pmc_mux: Put ACPI device using acpi_dev_put()
usb: typec: intel_pmc_mux: Add missed error check for devm_ioremap_resource()
usb: typec: intel_pmc_mux: Put fwnode in error case during ->probe()
usb: typec: tcpm: Do not finish VDM AMS for retrying Responses
usb: fix various gadget panics on 10gbps cabling
usb: fix various gadgets null ptr deref on 10gbps cabling.
usb: pci-quirks: disable D3cold on xhci suspend for s2idle on AMD Renoir
usb: f_ncm: only first packet of aggregate needs to start timer
USB: f_ncm: ncm_bitrate (speed) is unsigned
MAINTAINERS: usb: add entry for isp1760
...
Pull serial driver fix from Greg KH:
"A single 8250_exar serial driver fix for a reported problem with a
change that happened in 5.13-rc1.
It has been in linux-next with no reported problems"
* tag 'tty-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
serial: 8250_exar: Avoid NULL pointer dereference at ->exit()
Pull staging driver fixes from Greg KH:
"Two tiny staging driver fixes:
- ralink-gdma driver authorship information fixed up
- rtl8723bs driver fix for reported regression
Both have been in linux-next for a while with no reported problems"
* tag 'staging-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging:
staging: ralink-gdma: Remove incorrect author information
staging: rtl8723bs: Fix uninitialized variables
Pull driver core fix from Greg KH:
"A single debugfs fix for 5.13-rc6, fixing a bug in
debugfs_read_file_str() that showed up in 5.13-rc1.
It has been in linux-next for a full week with no
reported problems"
* tag 'driver-core-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core:
debugfs: Fix debugfs_read_file_str()
Pull char/misc driver fixes from Greg KH:
"Here are some small misc driver fixes for 5.13-rc6 that fix some
reported problems:
- Tiny phy driver fixes for reported issues
- rtsx regression for when the device suspended
- mhi driver fix for a use-after-free
All of these have been in linux-next for a few days with no reported
issues"
* tag 'char-misc-5.13-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc:
misc: rtsx: separate aspm mode into MODE_REG and MODE_CFG
bus: mhi: pci-generic: Fix hibernation
bus: mhi: pci_generic: Fix possible use-after-free in mhi_pci_remove()
bus: mhi: pci_generic: T99W175: update channel name from AT to DUN
phy: Sparx5 Eth SerDes: check return value after calling platform_get_resource()
phy: ralink: phy-mt7621-pci: drop 'of_match_ptr' to fix -Wunused-const-variable
phy: ti: Fix an error code in wiz_probe()
phy: phy-mtk-tphy: Fix some resource leaks in mtk_phy_init()
phy: cadence: Sierra: Fix error return code in cdns_sierra_phy_probe()
phy: usb: Fix misuse of IS_ENABLED
Pull pin control fixes from Linus Walleij:
- Fix some documentation warnings for Allwinner
- Fix duplicated GPIO groups on Qualcomm SDX55
- Fix a double enablement bug in the Ralink driver
- Fix the Qualcomm SC8180x Kconfig so the driver can be selected.
* tag 'pinctrl-v5.13-2' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl:
pinctrl: qcom: Make it possible to select SC8180x TLMM
pinctrl: ralink: rt2880: avoid to error in calls is pin is already enabled
pinctrl: qcom: Fix duplication in gpio_groups
pinctrl: aspeed: Fix minor documentation error
Pull block fixes from Jens Axboe:
"A few fixes that should go into 5.13:
- Fix a regression deadlock introduced in this release between open
and remove of a bdev (Christoph)
- Fix an async_xor md regression in this release (Xiao)
- Fix bcache oversized read issue (Coly)"
* tag 'block-5.13-2021-06-12' of git://git.kernel.dk/linux-block:
block: loop: fix deadlock between open and remove
async_xor: check src_offs is not NULL before updating it
bcache: avoid oversized read request in cache missing code path
bcache: remove bcache device self-defined readahead
Peter Zijlstra
Ingo Molnar
Lukasz Luba
Dietmar Eggemann
Vincent Guittot
Odin Ugedal
Linus Torvalds
Feng Tang