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932,869 commits

Author SHA1 Message Date
Linus Walleij
97cbaf2c82 tty: serial: cpm_uart: Convert to use GPIO descriptors
The CPM UART (PowerPC) has an open coded GPIO modem control
handling. Since I can't test this I can't just migrate it to
the serial mctrl GPIO helper library though I wish I could.
I do second best and convert it to GPIO descriptors at least.

Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20200229231842.247563-1-linus.walleij@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-06 13:16:16 +01:00
Linus Walleij
8145e85f82 tty: serial: lantiq: Drop GPIO include
Nothing in this driver uses the symbols from <linux/gpio.h>
so drop this include.

Cc: Rahul Tanwar <rahul.tanwar@linux.intel.com>
Cc: Songjun Wu <songjun.wu@linux.intel.com>
Cc: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Cc: John Crispin <john@phrozen.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20200229212331.174946-1-linus.walleij@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-06 13:16:16 +01:00
Linus Walleij
67f468d4ae tty: serial: atmel_serial: Drop GPIO includes
Nothing in this driver uses the symbols from these GPIO
includes so drop them. These are probably just historical
artifacts from befor mctrl_gpio was used.

Cc: Ludovic Desroches <ludovic.desroches@microchip.com>
Cc: Razvan Stefanescu <razvan.stefanescu@microchip.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Ludovic Desroches <ludovic.desroches@microchip.com>
Link: https://lore.kernel.org/r/20200229220941.205599-1-linus.walleij@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2020-03-06 13:16:16 +01:00
Qais Yousef
d94a9df490 sched/rt: Remove unnecessary push for unfit tasks
In task_woken_rt() and switched_to_rto() we try trigger push-pull if the
task is unfit.

But the logic is found lacking because if the task was the only one
running on the CPU, then rt_rq is not in overloaded state and won't
trigger a push.

The necessity of this logic was under a debate as well, a summary of
the discussion can be found in the following thread:

  https://lore.kernel.org/lkml/20200226160247.iqvdakiqbakk2llz@e107158-lin.cambridge.arm.com/

Remove the logic for now until a better approach is agreed upon.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 804d402fb6 ("sched/rt: Make RT capacity-aware")
Link: https://lkml.kernel.org/r/20200302132721.8353-6-qais.yousef@arm.com
2020-03-06 12:57:29 +01:00
Qais Yousef
98ca645f82 sched/rt: Allow pulling unfitting task
When implemented RT Capacity Awareness; the logic was done such that if
a task was running on a fitting CPU, then it was sticky and we would try
our best to keep it there.

But as Steve suggested, to adhere to the strict priority rules of RT
class; allow pulling an RT task to unfitting CPU to ensure it gets a
chance to run ASAP.

LINK: https://lore.kernel.org/lkml/20200203111451.0d1da58f@oasis.local.home/
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 804d402fb6 ("sched/rt: Make RT capacity-aware")
Link: https://lkml.kernel.org/r/20200302132721.8353-5-qais.yousef@arm.com
2020-03-06 12:57:28 +01:00
Qais Yousef
a1bd02e1f2 sched/rt: Optimize cpupri_find() on non-heterogenous systems
By introducing a new cpupri_find_fitness() function that takes the
fitness_fn as an argument and only called when asym_system static key is
enabled.

cpupri_find() is now a wrapper function that calls cpupri_find_fitness()
passing NULL as a fitness_fn, hence disabling the logic that handles
fitness by default.

LINK: https://lore.kernel.org/lkml/c0772fca-0a4b-c88d-fdf2-5715fcf8447b@arm.com/
Reported-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 804d402fb6 ("sched/rt: Make RT capacity-aware")
Link: https://lkml.kernel.org/r/20200302132721.8353-4-qais.yousef@arm.com
2020-03-06 12:57:27 +01:00
Qais Yousef
b28bc1e002 sched/rt: Re-instate old behavior in select_task_rq_rt()
When RT Capacity Aware support was added, the logic in select_task_rq_rt
was modified to force a search for a fitting CPU if the task currently
doesn't run on one.

But if the search failed, and the search was only triggered to fulfill
the fitness request; we could end up selecting a new CPU unnecessarily.

Fix this and re-instate the original behavior by ensuring we bail out
in that case.

This behavior change only affected asymmetric systems that are using
util_clamp to implement capacity aware. None asymmetric systems weren't
affected.

LINK: https://lore.kernel.org/lkml/20200218041620.GD28029@codeaurora.org/
Reported-by: Pavan Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 804d402fb6 ("sched/rt: Make RT capacity-aware")
Link: https://lkml.kernel.org/r/20200302132721.8353-3-qais.yousef@arm.com
2020-03-06 12:57:27 +01:00
Qais Yousef
d9cb236b94 sched/rt: cpupri_find: Implement fallback mechanism for !fit case
When searching for the best lowest_mask with a fitness_fn passed, make
sure we record the lowest_level that returns a valid lowest_mask so that
we can use that as a fallback in case we fail to find a fitting CPU at
all levels.

The intention in the original patch was not to allow a down migration to
unfitting CPU. But this missed the case where we are already running on
unfitting one.

With this change now RT tasks can still move between unfitting CPUs when
they're already running on such CPU.

And as Steve suggested; to adhere to the strict priority rules of RT, if
a task is already running on a fitting CPU but due to priority it can't
run on it, allow it to downmigrate to unfitting CPU so it can run.

Reported-by: Pavan Kondeti <pkondeti@codeaurora.org>
Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 804d402fb6 ("sched/rt: Make RT capacity-aware")
Link: https://lkml.kernel.org/r/20200302132721.8353-2-qais.yousef@arm.com
Link: https://lore.kernel.org/lkml/20200203142712.a7yvlyo2y3le5cpn@e107158-lin/
2020-03-06 12:57:26 +01:00
Vincent Guittot
5ab297bab9 sched/fair: Fix reordering of enqueue/dequeue_task_fair()
Even when a cgroup is throttled, the group se of a child cgroup can still
be enqueued and its gse->on_rq stays true. When a task is enqueued on such
child, we still have to update the load_avg and increase
h_nr_running of the throttled cfs. Nevertheless, the 1st
for_each_sched_entity() loop is skipped because of gse->on_rq == true and the
2nd loop because the cfs is throttled whereas we have to update both
load_avg with the old h_nr_running and increase h_nr_running in such case.

The same sequence can happen during dequeue when se moves to parent before
breaking in the 1st loop.

Note that the update of load_avg will effectively happen only once in order
to sync up to the throttled time. Next call for updating load_avg will stop
early because the clock stays unchanged.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 6d4d22468d ("sched/fair: Reorder enqueue/dequeue_task_fair path")
Link: https://lkml.kernel.org/r/20200306084208.12583-1-vincent.guittot@linaro.org
2020-03-06 12:57:25 +01:00
Vincent Guittot
6212437f0f sched/fair: Fix runnable_avg for throttled cfs
When a cfs_rq is throttled, its group entity is dequeued and its running
tasks are removed. We must update runnable_avg with the old h_nr_running
and update group_se->runnable_weight with the new h_nr_running at each
level of the hierarchy.

Reviewed-by: Ben Segall <bsegall@google.com>
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 9f68395333 ("sched/pelt: Add a new runnable average signal")
Link: https://lkml.kernel.org/r/20200227154115.8332-1-vincent.guittot@linaro.org
2020-03-06 12:57:25 +01:00
Yu Chen
ba4f7bc1de sched/deadline: Make two functions static
Since commit 06a76fe08d ("sched/deadline: Move DL related code
from sched/core.c to sched/deadline.c"), DL related code moved to
deadline.c.

Make the following two functions static since they're only used in
deadline.c:

	dl_change_utilization()
	init_dl_rq_bw_ratio()

Signed-off-by: Yu Chen <chen.yu@easystack.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200228100329.16927-1-chen.yu@easystack.cn
2020-03-06 12:57:24 +01:00
Valentin Schneider
6f693dd5be arm64: defconfig: enable CONFIG_SCHED_SMT
The (CFS) scheduler has some extra logic catering to systems with SMT, but
that logic won't be compiled in unless the above config is set.

Note that the SMT-centric codepaths are gated by the sched_smt_present
static key, and the SMT sched_domains will only survive if the platform has
SMT. As such, the only impact on !SMT platforms should be a slightly
bigger kernel - no behavioural change.

Distro kernels already enable it, which makes sense since there already are
things like ThunderX2 out in the wild. Enable it for the defconfig.

Some deltas
===========

FWIW my ELF symbol table diff looks something like this:

  NAME                                BEFORE    AFTER     DELTA
  update_sd_lb_stats.constprop.135    0         1864      +1864
  find_idlest_group.isra.115          0         1808      +1808
  update_numa_stats.isra.121          0         628       +628
  select_task_rq_fair                 3236      3732      +496
  compute_energy.isra.112             0         420       +420
  score_nearby_nodes.part.120         0         380       +380
  __update_idle_core                  0         232       +232
  nohz_balance_exit_idle.part.127     0         216       +216
  sched_slice.isra.99                 0         172       +172
  update_load_avg.part.107            0         116       +116
  wakeup_preempt_entity.isra.101      0         92        +92
  sched_cpu_activate                  340       396       +56
  pick_next_task_idle                 8         56        +48
  sched_cpu_deactivate                252       292       +40
  show_smt_active                     44        80        +36
  cpu_smt_mask                        0         28        +28
  set_next_task_idle                  4         32        +28
  task_numa_work                      680       692       +12
  cpu_smt_flags                       0         8         +8
  enqueue_task_fair                   2608      2612      +4
  wakeup_preempt_entity.isra.104      92        0         -92
  update_load_avg                     1028      932       -96
  task_numa_migrate                   1824      1728      -96
  sched_slice.isra.102                172       0         -172
  nohz_balance_exit_idle.part.130     216       0         -216
  task_numa_find_cpu                  2116      1868      -248
  score_nearby_nodes.part.123         380       0         -380
  compute_energy.isra.115             420       0         -420
  update_numa_stats.isra.124          472       0         -472
  find_idlest_group.isra.118          1808      0         -1808
  update_sd_lb_stats.constprop.138    1864      0         -1864
  ------------------------------------------------------------------
  DELTA SUM                                               +820

As for the sched_domains, this is on a hikey960:

before:
  $ cat /proc/sys/kernel/sched_domain/cpu*/domain*/name | sort | uniq
  DIE
  MC

after:
  $ cat /proc/sys/kernel/sched_domain/cpu*/domain*/name | sort | uniq
  DIE
  MC

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200227191433.31994-3-valentin.schneider@arm.com
2020-03-06 12:57:23 +01:00
Valentin Schneider
38502ab4bf sched/topology: Don't enable EAS on SMT systems
EAS already requires asymmetric CPU capacities to be enabled, and mixing
this with SMT is an aberration, but better be safe than sorry.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Acked-by: Quentin Perret <qperret@google.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200227191433.31994-2-valentin.schneider@arm.com
2020-03-06 12:57:23 +01:00
Mel Gorman
0621df3154 sched/numa: Acquire RCU lock for checking idle cores during NUMA balancing
Qian Cai reported the following bug:

  The linux-next commit ff7db0bf24 ("sched/numa: Prefer using an idle CPU as a
  migration target instead of comparing tasks") introduced a boot warning,

  [   86.520534][    T1] WARNING: suspicious RCU usage
  [   86.520540][    T1] 5.6.0-rc3-next-20200227 #7 Not tainted
  [   86.520545][    T1] -----------------------------
  [   86.520551][    T1] kernel/sched/fair.c:5914 suspicious rcu_dereference_check() usage!
  [   86.520555][    T1]
  [   86.520555][    T1] other info that might help us debug this:
  [   86.520555][    T1]
  [   86.520561][    T1]
  [   86.520561][    T1] rcu_scheduler_active = 2, debug_locks = 1
  [   86.520567][    T1] 1 lock held by systemd/1:
  [   86.520571][    T1]  #0: ffff8887f4b14848 (&mm->mmap_sem#2){++++}, at: do_page_fault+0x1d2/0x998
  [   86.520594][    T1]
  [   86.520594][    T1] stack backtrace:
  [   86.520602][    T1] CPU: 1 PID: 1 Comm: systemd Not tainted 5.6.0-rc3-next-20200227 #7

task_numa_migrate() checks for idle cores when updating NUMA-related statistics.
This relies on reading a RCU-protected structure in test_idle_cores() via this
call chain

task_numa_migrate
  -> update_numa_stats
    -> numa_idle_core
      -> test_idle_cores

While the locking could be fine-grained, it is more appropriate to acquire
the RCU lock for the entire scan of the domain. This patch removes the
warning triggered at boot time.

Reported-by: Qian Cai <cai@lca.pw>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: ff7db0bf24 ("sched/numa: Prefer using an idle CPU as a migration target instead of comparing tasks")
Link: https://lkml.kernel.org/r/20200227191804.GJ3818@techsingularity.net
2020-03-06 12:57:22 +01:00
Valentin Schneider
76c389ab2b sched/fair: Fix kernel build warning in test_idle_cores() for !SMT NUMA
Building against the tip/sched/core as ff7db0bf24 ("sched/numa: Prefer
using an idle CPU as a migration target instead of comparing tasks") with
the arm64 defconfig (which doesn't have CONFIG_SCHED_SMT set) leads to:

  kernel/sched/fair.c:1525:20: warning: 'test_idle_cores' declared 'static' but never defined [-Wunused-function]
   static inline bool test_idle_cores(int cpu, bool def);
		      ^~~~~~~~~~~~~~~

Rather than define it in its own CONFIG_SCHED_SMT #define island, bunch it
up with test_idle_cores().

Reported-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
[mgorman@techsingularity.net: Edit changelog, minor style change]
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: ff7db0bf24 ("sched/numa: Prefer using an idle CPU as a migration target instead of comparing tasks")
Link: https://lkml.kernel.org/r/20200303110258.1092-3-mgorman@techsingularity.net
2020-03-06 12:57:22 +01:00
Thara Gopinath
05289b90c2 sched/fair: Enable tuning of decay period
Thermal pressure follows pelt signals which means the decay period for
thermal pressure is the default pelt decay period. Depending on SoC
characteristics and thermal activity, it might be beneficial to decay
thermal pressure slower, but still in-tune with the pelt signals.  One way
to achieve this is to provide a command line parameter to set a decay
shift parameter to an integer between 0 and 10.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-10-thara.gopinath@linaro.org
2020-03-06 12:57:21 +01:00
Thara Gopinath
f12e4f66ab thermal/cpu-cooling: Update thermal pressure in case of a maximum frequency capping
Thermal governors can request for a CPU's maximum supported frequency to
be capped in case of an overheat event. This in turn means that the
maximum capacity available for tasks to run on the particular CPU is
reduced. Delta between the original maximum capacity and capped maximum
capacity is known as thermal pressure. Enable cpufreq cooling device to
update the thermal pressure in event of a capped maximum frequency.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-9-thara.gopinath@linaro.org
2020-03-06 12:57:21 +01:00
Thara Gopinath
467b7d01c4 sched/fair: Update cpu_capacity to reflect thermal pressure
cpu_capacity initially reflects the maximum possible capacity of a CPU.
Thermal pressure on a CPU means this maximum possible capacity is
unavailable due to thermal events. This patch subtracts the average
thermal pressure for a CPU from its maximum possible capacity so that
cpu_capacity reflects the remaining maximum capacity.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-8-thara.gopinath@linaro.org
2020-03-06 12:57:20 +01:00
Thara Gopinath
b4eccf5f8e sched/fair: Enable periodic update of average thermal pressure
Introduce support in scheduler periodic tick and other CFS bookkeeping
APIs to trigger the process of computing average thermal pressure for a
CPU. Also consider avg_thermal.load_avg in others_have_blocked which
allows for decay of pelt signals.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-7-thara.gopinath@linaro.org
2020-03-06 12:57:20 +01:00
Thara Gopinath
8eab879c54 arm/topology: Populate arch_scale_thermal_pressure() for ARM platforms
Hook up topology_get_thermal_pressure to arch_scale_thermal_pressure thus
enabling scheduler to retrieve instantaneous thermal pressure of a CPU.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-6-thara.gopinath@linaro.org
2020-03-06 12:57:19 +01:00
Thara Gopinath
ae1677c0bb arm64/topology: Populate arch_scale_thermal_pressure() for arm64 platforms
Hook up topology_get_thermal_pressure to arch_scale_thermal_pressure thus
enabling scheduler to retrieve instantaneous thermal pressure of a CPU.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-5-thara.gopinath@linaro.org
2020-03-06 12:57:19 +01:00
Thara Gopinath
ad58cc5cc5 drivers/base/arch_topology: Add infrastructure to store and update instantaneous thermal pressure
Add architecture specific APIs to update and track thermal pressure on a
per CPU basis. A per CPU variable thermal_pressure is introduced to keep
track of instantaneous per CPU thermal pressure. Thermal pressure is the
delta between maximum capacity and capped capacity due to a thermal event.

topology_get_thermal_pressure can be hooked into the scheduler specified
arch_scale_thermal_pressure to retrieve instantaneous thermal pressure of
a CPU.

arch_set_thermal_pressure can be used to update the thermal pressure.

Considering topology_get_thermal_pressure reads thermal_pressure and
arch_set_thermal_pressure writes into thermal_pressure, one can argue for
some sort of locking mechanism to avoid a stale value.  But considering
topology_get_thermal_pressure can be called from a system critical path
like scheduler tick function, a locking mechanism is not ideal. This means
that it is possible the thermal_pressure value used to calculate average
thermal pressure for a CPU can be stale for up to 1 tick period.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-4-thara.gopinath@linaro.org
2020-03-06 12:57:18 +01:00
Thara Gopinath
36a0df85d2 sched/topology: Add callback to read per CPU thermal pressure
Introduce the arch_scale_thermal_pressure() callback to retrieve per CPU thermal
pressure.

Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-3-thara.gopinath@linaro.org
2020-03-06 12:57:17 +01:00
Thara Gopinath
765047932f sched/pelt: Add support to track thermal pressure
Extrapolating on the existing framework to track rt/dl utilization using
pelt signals, add a similar mechanism to track thermal pressure. The
difference here from rt/dl utilization tracking is that, instead of
tracking time spent by a CPU running a RT/DL task through util_avg, the
average thermal pressure is tracked through load_avg. This is because
thermal pressure signal is weighted time "delta" capacity unlike util_avg
which is binary. "delta capacity" here means delta between the actual
capacity of a CPU and the decreased capacity a CPU due to a thermal event.

In order to track average thermal pressure, a new sched_avg variable
avg_thermal is introduced. Function update_thermal_load_avg can be called
to do the periodic bookkeeping (accumulate, decay and average) of the
thermal pressure.

Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Thara Gopinath <thara.gopinath@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200222005213.3873-2-thara.gopinath@linaro.org
2020-03-06 12:57:17 +01:00
Chris Wilson
f1dfdab694 sched/vtime: Prevent unstable evaluation of WARN(vtime->state)
As the vtime is sampled under loose seqcount protection by kcpustat, the
vtime fields may change as the code flows. Where logic dictates a field
has a static value, use a READ_ONCE.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Fixes: 74722bb223 ("sched/vtime: Bring up complete kcpustat accessor")
Link: https://lkml.kernel.org/r/20200123180849.28486-1-frederic@kernel.org
2020-03-06 12:57:16 +01:00
Lukas Bulwahn
0be38b10f0 MAINTAINERS: adjust to reservation.h renaming
Commit 52791eeec1 ("dma-buf: rename reservation_object to dma_resv")
renamed include/linux/reservation.h to include/linux/dma-resv.h, but
missed the reference in the MAINTAINERS entry.

Since then, ./scripts/get_maintainer.pl --self-test complains:

  warning: no file matches F: include/linux/reservation.h

Adjust the DMA BUFFER SHARING FRAMEWORK entry in MAINTAINERS.

Co-developed-by: Sebastian Duda <sebastian.duda@fau.de>
Signed-off-by: Sebastian Duda <sebastian.duda@fau.de>
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/356414/
Signed-off-by: Christian König <christian.koenig@amd.com>
2020-03-06 12:52:46 +01:00
Ingo Molnar
1b10d388d0 Merge branch 'linus' into sched/core, to pick up fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-06 12:49:56 +01:00
Ian Rogers
441b62acd9 tools: Fix off-by 1 relative directory includes
This is currently working due to extra include paths in the build.

Committer testing:

  $ cd tools/include/uapi/asm/

Before this patch:

  $ ls -la ../../arch/x86/include/uapi/asm/errno.h
  ls: cannot access '../../arch/x86/include/uapi/asm/errno.h': No such file or directory
  $

After this patch;

  $ ls -la ../../../arch/x86/include/uapi/asm/errno.h
  -rw-rw-r--. 1 acme acme 31 Feb 20 12:42 ../../../arch/x86/include/uapi/asm/errno.h
  $

Check that that is still under tools/, i.e. hasn't escaped into the main
kernel sources:

  $ cd ../../../arch/x86/include/uapi/asm/
  $ pwd
  /home/acme/git/perf/tools/arch/x86/include/uapi/asm
  $

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexios Zavras <alexios.zavras@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Igor Lubashev <ilubashe@akamai.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Wei Li <liwei391@huawei.com>
Link: http://lore.kernel.org/lkml/20200306071110.130202-2-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-03-06 08:36:46 -03:00
John Garry
3f5777fbaf perf jevents: Fix leak of mapfile memory
The memory for global pointer is never freed during normal program
execution, so let's do that in the main function exit as a good
programming practice.

A stray blank line is also removed.

Reported-by: Jiri Olsa <jolsa@redhat.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: James Clark <james.clark@arm.com>
Cc: Joakim Zhang <qiangqing.zhang@nxp.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Will Deacon <will@kernel.org>
Cc: linuxarm@huawei.com
Link: http://lore.kernel.org/lkml/1583406486-154841-2-git-send-email-john.garry@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-03-06 08:30:47 -03:00
Tommi Rantala
7b919a5310 perf bench: Clear struct sigaction before sigaction() syscall
Avoid garbage in sigaction structs used in sigaction() syscalls.
Valgrind is complaining about it.

Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Changbin Du <changbin.du@intel.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lore.kernel.org/lkml/20200305083714.9381-4-tommi.t.rantala@nokia.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-03-06 08:30:47 -03:00
Tommi Rantala
f649bd9dd5 perf bench futex-wake: Restore thread count default to online CPU count
Since commit 3b2323c2c1 ("perf bench futex: Use cpumaps") the default
number of threads the benchmark uses got changed from number of online
CPUs to zero:

  $ perf bench futex wake
  # Running 'futex/wake' benchmark:
  Run summary [PID 15930]: blocking on 0 threads (at [private] futex 0x558b8ee4bfac), waking up 1 at a time.
  [Run 1]: Wokeup 0 of 0 threads in 0.0000 ms
  [...]
  [Run 10]: Wokeup 0 of 0 threads in 0.0000 ms
  Wokeup 0 of 0 threads in 0.0004 ms (+-40.82%)

Restore the old behavior by grabbing the number of online CPUs via
cpu->nr:

  $ perf bench futex wake
  # Running 'futex/wake' benchmark:
  Run summary [PID 18356]: blocking on 8 threads (at [private] futex 0xb3e62c), waking up 1 at a time.
  [Run 1]: Wokeup 8 of 8 threads in 0.0260 ms
  [...]
  [Run 10]: Wokeup 8 of 8 threads in 0.0270 ms
  Wokeup 8 of 8 threads in 0.0419 ms (+-24.35%)

Fixes: 3b2323c2c1 ("perf bench futex: Use cpumaps")
Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Darren Hart <dvhart@infradead.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lore.kernel.org/lkml/20200305083714.9381-3-tommi.t.rantala@nokia.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-03-06 08:30:47 -03:00
Tommi Rantala
29b4f5f188 perf top: Fix stdio interface input handling with glibc 2.28+
Since glibc 2.28 when running 'perf top --stdio', input handling no
longer works, but hitting any key always just prints the "Mapped keys"
help text.

To fix it, call clearerr() in the display_thread() loop to clear any EOF
sticky errors, as instructed in the glibc NEWS file
(https://sourceware.org/git/?p=glibc.git;a=blob;f=NEWS):

 * All stdio functions now treat end-of-file as a sticky condition.  If you
   read from a file until EOF, and then the file is enlarged by another
   process, you must call clearerr or another function with the same effect
   (e.g. fseek, rewind) before you can read the additional data.  This
   corrects a longstanding C99 conformance bug.  It is most likely to affect
   programs that use stdio to read interactive input from a terminal.
   (Bug #1190.)

Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200305083714.9381-2-tommi.t.rantala@nokia.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-03-06 08:30:47 -03:00
Nick Desaulniers
cfd3bc752a perf diff: Fix undefined string comparision spotted by clang's -Wstring-compare
clang warns:

  util/block-info.c:298:18: error: result of comparison against a string
  literal is unspecified (use an explicit string comparison function
  instead) [-Werror,-Wstring-compare]
          if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                          ^  ~~~~~~~~~~~~~~~
  util/block-info.c:298:51: error: result of comparison against a string
  literal is unspecified (use an explicit string comparison function
  instead) [-Werror,-Wstring-compare]
          if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                           ^  ~~~~~~~~~~~~~~~
  util/block-info.c:298:18: error: result of comparison against a string
  literal is unspecified (use an explicit string
  comparison function instead) [-Werror,-Wstring-compare]
          if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                          ^  ~~~~~~~~~~~~~~~
  util/block-info.c:298:51: error: result of comparison against a string
  literal is unspecified (use an explicit string comparison function
  instead) [-Werror,-Wstring-compare]
          if ((start_line != SRCLINE_UNKNOWN) && (end_line != SRCLINE_UNKNOWN)) {
                                                           ^  ~~~~~~~~~~~~~~~
  util/map.c:434:15: error: result of comparison against a string literal
  is unspecified (use an explicit string comparison function instead)
  [-Werror,-Wstring-compare]
                  if (srcline != SRCLINE_UNKNOWN)
                              ^  ~~~~~~~~~~~~~~~

Reviewer Notes:

Looks good to me. Some more context:
https://clang.llvm.org/docs/DiagnosticsReference.html#wstring-compare
The spec says:
J.1 Unspecified behavior
The following are unspecified:
.. Whether two string literals result in distinct arrays (6.4.5).

Signed-off-by: Nick Desaulniers <nick.desaulniers@gmail.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Changbin Du <changbin.du@intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: John Keeping <john@metanate.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: clang-built-linux@googlegroups.com
Link: https://github.com/ClangBuiltLinux/linux/issues/900
Link: http://lore.kernel.org/lkml/20200223193456.25291-1-nick.desaulniers@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2020-03-06 08:30:29 -03:00
Randy Dunlap
9b6c80be97 drm: unbreak the DRM menu, broken by DRM_EXPORT_FOR_TESTS
Unbreak the DRM menu. This Kconfig symbol does not depend on DRM,
so the menu is broken at that point.

Move the symbol to a location in the Kconfig file so that it does
not break the dependency continuity.

Fixes: 6349120ddc ("drm: Move EXPORT_SYMBOL_FOR_TESTS_ONLY under a separate Kconfig")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/04221997-79ba-f8a2-4f2d-3c3d9f5219bc@infradead.org
2020-03-06 11:15:43 +00:00
Chris Wilson
7be1b9b8e9 drm/mm: Break long searches in fragmented address spaces
We try hard to select a suitable hole in the drm_mm first time. But if
that is unsuccessful, we then have to look at neighbouring nodes, and
this requires traversing the rbtree. Walking the rbtree can be slow
(much slower than a linear list for deep trees), and if the drm_mm has
been purposefully fragmented our search can be trapped for a long, long
time. For non-preemptible kernels, we need to break up long CPU bound
sections by manually checking for cond_resched(); similarly we should
also bail out if we have been told to terminate. (In an ideal world, we
would break for any signal, but we need to trade off having to perform
the search again after ERESTARTSYS, which again may form a trap of
making no forward progress.)

Reported-by: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Zbigniew Kempczyński <zbigniew.kempczynski@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Andi Shyti <andi.shyti@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200207151720.2812125-1-chris@chris-wilson.co.uk
2020-03-06 11:15:43 +00:00
Thomas Bogendoerfer
95dbf14b23 ALSA: sgio2audio: Remove usage of dropped hw_params/hw_free functions
Commit ee88f4ebe5 ("ALSA: mips: Use managed buffer allocation") removed
superfluous hw_params/hw_free callbacks, but forgot to remove them where
they were used.

Fixes: ee88f4ebe5 ("ALSA: mips: Use managed buffer allocation")
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Link: https://lore.kernel.org/r/20200306105837.31523-1-tsbogend@alpha.franken.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
2020-03-06 12:06:41 +01:00
Chris Wilson
ef398881d2 drm/i915/gem: Limit struct_mutex to eb_reserve
We only need to serialise the multiple pinning during the eb_reserve
phase. Ideally this would be using the vm->mutex as an outer lock, or
using a composite global mutex (ww_mutex), but at the moment we are
using struct_mutex for the group.

Closes: https://gitlab.freedesktop.org/drm/intel/issues/1381
Fixes: 003d8b9143 ("drm/i915/gem: Only call eb_lookup_vma once during execbuf ioctl")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200306071614.2846708-3-chris@chris-wilson.co.uk
2020-03-06 10:58:05 +00:00
Chris Wilson
26fc4e4ba1 drm/i915: Always propagate the invocation to i915_schedule
We only call i915_schedule() when we know we have changed the priority
on a request and so require to propagate any change in priority to its
signalers (for PI). By unconditionally checking all of our signalers, we
avoid skipping changes made prior to construction of the request (as the
request may be waited upon before submission when used in parallel).

References: https://gitlab.freedesktop.org/drm/intel/issues/1318
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200306071614.2846708-2-chris@chris-wilson.co.uk
2020-03-06 10:58:05 +00:00
Ian Rogers
95ed6c707f perf/cgroup: Order events in RB tree by cgroup id
If one is monitoring 6 events on 20 cgroups the per-CPU RB tree will
hold 120 events. The scheduling in of the events currently iterates
over all events looking to see which events match the task's cgroup or
its cgroup hierarchy. If a task is in 1 cgroup with 6 events, then 114
events are considered unnecessarily.

This change orders events in the RB tree by cgroup id if it is present.
This means scheduling in may go directly to events associated with the
task's cgroup if one is present. The per-CPU iterator storage in
visit_groups_merge is sized sufficent for an iterator per cgroup depth,
where different iterators are needed for the task's cgroup and parent
cgroups. By considering the set of iterators when visiting, the lowest
group_index event may be selected and the insertion order group_index
property is maintained. This also allows event rotation to function
correctly, as although events are grouped into a cgroup, rotation always
selects the lowest group_index event to rotate (delete/insert into the
tree) and the min heap of iterators make it so that the group_index order
is maintained.

Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20190724223746.153620-3-irogers@google.com
2020-03-06 11:57:01 +01:00
Ian Rogers
c2283c9368 perf/cgroup: Grow per perf_cpu_context heap storage
Allow the per-CPU min heap storage to have sufficient space for per-cgroup
iterators.

Based-on-work-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200214075133.181299-6-irogers@google.com
2020-03-06 11:57:00 +01:00
Ian Rogers
836196beb3 perf/core: Add per perf_cpu_context min_heap storage
The storage required for visit_groups_merge's min heap needs to vary in
order to support more iterators, such as when multiple nested cgroups'
events are being visited. This change allows for 2 iterators and doesn't
support growth.

Based-on-work-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200214075133.181299-5-irogers@google.com
2020-03-06 11:57:00 +01:00
Ian Rogers
6eef8a7116 perf/core: Use min_heap in visit_groups_merge()
visit_groups_merge will pick the next event based on when it was
inserted in to the context (perf_event group_index). Events may be per CPU
or for any CPU, but in the future we'd also like to have per cgroup events
to avoid searching all events for the events to schedule for a cgroup.
Introduce a min heap for the events that maintains a property that the
earliest inserted event is always at the 0th element. Initialize the heap
with per-CPU and any-CPU events for the context.

Based-on-work-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200214075133.181299-4-irogers@google.com
2020-03-06 11:56:59 +01:00
Ian Rogers
6e24628d78 lib: Introduce generic min-heap
Supports push, pop and converting an array into a heap. If the sense of
the compare function is inverted then it can provide a max-heap.

Based-on-work-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200214075133.181299-3-irogers@google.com
2020-03-06 11:56:59 +01:00
Peter Zijlstra
98add2af89 perf/cgroup: Reorder perf_cgroup_connect()
Move perf_cgroup_connect() after perf_event_alloc(), such that we can
find/use the PMU's cpu context.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ian Rogers <irogers@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lkml.kernel.org/r/20200214075133.181299-2-irogers@google.com
2020-03-06 11:56:58 +01:00
Peter Zijlstra
2c2366c754 perf/core: Remove 'struct sched_in_data'
We can deduce the ctx and cpuctx from the event, no need to pass them
along. Remove the structure and pass in can_add_hw directly.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-06 11:56:58 +01:00
Peter Zijlstra
ab6f824cfd perf/core: Unify {pinned,flexible}_sched_in()
Less is more; unify the two very nearly identical function.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-06 11:56:55 +01:00
Ingo Molnar
1941011a8b Merge branch 'perf/urgent' into perf/core, to pick up the latest fixes
Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-06 11:56:40 +01:00
Chris Wilson
1eaa251b66 drm/i915: Assert requests within a context are submitted in order
Check the flow of requests into the hardware to verify that are
submitted in order along their timeline.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200306071614.2846708-1-chris@chris-wilson.co.uk
2020-03-06 10:53:54 +00:00
Gustavo A. R. Silva
78a7b61aef drm/bridge/mhl.h: Replace zero-length array with flexible-array member
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305110011.GA21056@embeddedor
2020-03-06 11:52:01 +01:00
Gustavo A. R. Silva
5b2adbddf2 drm/vc4/vc4_drv.h: Replace zero-length array with flexible-array member
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array member[1][2],
introduced in C99:

struct foo {
        int stuff;
        struct boo array[];
};

By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.

Also, notice that, dynamic memory allocations won't be affected by
this change:

"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]

This issue was found with the help of Coccinelle.

[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
[2] https://github.com/KSPP/linux/issues/21
[3] commit 7649773293 ("cxgb3/l2t: Fix undefined behaviour")

Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200305105707.GA19261@embeddedor
2020-03-06 11:50:17 +01:00