linux-stable.git/kernel/sched/psi.c, branch linux-5.2.y

sched/psi: Correct overly pessimistic size calculation

2019-10-05T11:13:55+00:00

[ Upstream commit 4adcdcea717cb2d8436bef00dd689aa5bc76f11b ]

When passing a equal or more then 32 bytes long string to psi_write(),
psi_write() copies 31 bytes to its buf and overwrites buf[30]
with '\0'. Which makes the input string 1 byte shorter than
it should be.

Fix it by copying sizeof(buf) bytes when nbytes >= sizeof(buf).

This does not cause problems in normal use case like:
"some 500000 10000000" or "full 500000 10000000" because they
are less than 32 bytes in length.

	/* assuming nbytes == 35 */
	char buf[32];

	buf_size = min(nbytes, (sizeof(buf) - 1)); /* buf_size = 31 */
	if (copy_from_user(buf, user_buf, buf_size))
		return -EFAULT;

	buf[buf_size - 1] = '\0'; /* buf[30] = '\0' */

Before:

 %cd /proc/pressure/
 %echo "123456789|123456789|123456789|1234" > memory
 [   22.473497] nbytes=35,buf_size=31
 [   22.473775] 123456789|123456789|123456789| (print 30 chars)
 %sh: write error: Invalid argument

 %echo "123456789|123456789|123456789|1" > memory
 [   64.916162] nbytes=32,buf_size=31
 [   64.916331] 123456789|123456789|123456789| (print 30 chars)
 %sh: write error: Invalid argument

After:

 %cd /proc/pressure/
 %echo "123456789|123456789|123456789|1234" > memory
 [  254.837863] nbytes=35,buf_size=32
 [  254.838541] 123456789|123456789|123456789|1 (print 31 chars)
 %sh: write error: Invalid argument

 %echo "123456789|123456789|123456789|1" > memory
 [ 9965.714935] nbytes=32,buf_size=32
 [ 9965.715096] 123456789|123456789|123456789|1 (print 31 chars)
 %sh: write error: Invalid argument

Also remove the superfluous parentheses.

Signed-off-by: Miles Chen 
Cc: 
Cc: 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Thomas Gleixner 
Link: https://lkml.kernel.org/r/20190912103452.13281-1-miles.chen@mediatek.com
Signed-off-by: Ingo Molnar 
Signed-off-by: Sasha Levin

psi: get poll_work to run when calling poll syscall next time

2019-08-29T06:30:24+00:00

commit 7b2b55da1db10a5525460633ae4b6fb0be060c41 upstream.

Only when calling the poll syscall the first time can user receive
POLLPRI correctly.  After that, user always fails to acquire the event
signal.

Reproduce case:
 1. Get the monitor code in Documentation/accounting/psi.txt
 2. Run it, and wait for the event triggered.
 3. Kill and restart the process.

The question is why we can end up with poll_scheduled = 1 but the work
not running (which would reset it to 0).  And the answer is because the
scheduling side sees group->poll_kworker under RCU protection and then
schedules it, but here we cancel the work and destroy the worker.  The
cancel needs to pair with resetting the poll_scheduled flag.

Link: http://lkml.kernel.org/r/1566357985-97781-1-git-send-email-joseph.qi@linux.alibaba.com
Signed-off-by: Jason Xing 
Signed-off-by: Joseph Qi 
Reviewed-by: Caspar Zhang 
Reviewed-by: Suren Baghdasaryan 
Acked-by: Johannes Weiner 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds 
Signed-off-by: Greg Kroah-Hartman

sched/psi: Do not require setsched permission from the trigger creator

2019-08-29T06:30:15+00:00

[ Upstream commit 04e048cf09d7b5fc995817cdc5ae1acd4482429c ]

When a process creates a new trigger by writing into /proc/pressure/*
files, permissions to write such a file should be used to determine whether
the process is allowed to do so or not. Current implementation would also
require such a process to have setsched capability. Setting of psi trigger
thread's scheduling policy is an implementation detail and should not be
exposed to the user level. Remove the permission check by using _nocheck
version of the function.

Suggested-by: Nick Kralevich 
Signed-off-by: Suren Baghdasaryan 
Signed-off-by: Peter Zijlstra (Intel) 
Cc: lizefan@huawei.com
Cc: mingo@redhat.com
Cc: akpm@linux-foundation.org
Cc: kernel-team@android.com
Cc: dennisszhou@gmail.com
Cc: dennis@kernel.org
Cc: hannes@cmpxchg.org
Cc: axboe@kernel.dk
Link: https://lkml.kernel.org/r/20190730013310.162367-1-surenb@google.com
Signed-off-by: Sasha Levin

sched/psi: Reduce psimon FIFO priority

2019-08-29T06:30:15+00:00

[ Upstream commit 14f5c7b46a41a595fc61db37f55721714729e59e ]

PSI defaults to a FIFO-99 thread, reduce this to FIFO-1.

FIFO-99 is the very highest priority available to SCHED_FIFO and
it not a suitable default; it would indicate the psi work is the
most important work on the machine.

Since Real-Time tasks will have pre-allocated memory and locked it in
place, Real-Time tasks do not care about PSI. All it needs is to be
above OTHER.

Signed-off-by: Peter Zijlstra (Intel) 
Acked-by: Johannes Weiner 
Tested-by: Suren Baghdasaryan 
Cc: Thomas Gleixner 
Signed-off-by: Sasha Levin

kernel/sched/psi.c: expose pressure metrics on root cgroup

2019-05-15T02:52:48+00:00

Pressure metrics are already recorded and exposed in procfs for the
entire system, but any tool which monitors cgroup pressure has to
special case the root cgroup to read from procfs.  This patch exposes
the already recorded pressure metrics on the root cgroup.

Link: http://lkml.kernel.org/r/20190510174938.3361741-1-dschatzberg@fb.com
Signed-off-by: Dan Schatzberg 
Acked-by: Johannes Weiner 
Cc: Tejun Heo 
Cc: Li Zefan 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

psi: introduce psi monitor

2019-05-15T02:52:48+00:00

Psi monitor aims to provide a low-latency short-term pressure detection
mechanism configurable by users.  It allows users to monitor psi metrics
growth and trigger events whenever a metric raises above user-defined
threshold within user-defined time window.

Time window and threshold are both expressed in usecs.  Multiple psi
resources with different thresholds and window sizes can be monitored
concurrently.

Psi monitors activate when system enters stall state for the monitored
psi metric and deactivate upon exit from the stall state.  While system
is in the stall state psi signal growth is monitored at a rate of 10
times per tracking window.  Min window size is 500ms, therefore the min
monitoring interval is 50ms.  Max window size is 10s with monitoring
interval of 1s.

When activated psi monitor stays active for at least the duration of one
tracking window to avoid repeated activations/deactivations when psi
signal is bouncing.

Notifications to the users are rate-limited to one per tracking window.

Link: http://lkml.kernel.org/r/20190319235619.260832-8-surenb@google.com
Signed-off-by: Suren Baghdasaryan 
Signed-off-by: Johannes Weiner 
Cc: Dennis Zhou 
Cc: Ingo Molnar 
Cc: Jens Axboe 
Cc: Li Zefan 
Cc: Peter Zijlstra 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

psi: track changed states

2019-05-15T02:52:48+00:00

Introduce changed_states parameter into collect_percpu_times to track
the states changed since the last update.

This will be needed to detect whether polled states activated in the
monitor patch.

Link: http://lkml.kernel.org/r/20190319235619.260832-6-surenb@google.com
Signed-off-by: Suren Baghdasaryan 
Acked-by: Johannes Weiner 
Cc: Dennis Zhou 
Cc: Ingo Molnar 
Cc: Jens Axboe 
Cc: Li Zefan 
Cc: Peter Zijlstra 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

psi: split update_stats into parts

2019-05-15T02:52:47+00:00

Split update_stats into collect_percpu_times and update_averages for
collect_percpu_times to be reused later inside psi monitor.

Link: http://lkml.kernel.org/r/20190319235619.260832-5-surenb@google.com
Signed-off-by: Suren Baghdasaryan 
Acked-by: Johannes Weiner 
Cc: Dennis Zhou 
Cc: Ingo Molnar 
Cc: Jens Axboe 
Cc: Li Zefan 
Cc: Peter Zijlstra 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

psi: rename psi fields in preparation for psi trigger addition

2019-05-15T02:52:47+00:00

Rename psi_group structure member fields used for calculating psi totals
and averages for clear distinction between them and for trigger-related
fields that will be added by "psi: introduce psi monitor".

[surenb@google.com: v6]
  Link: http://lkml.kernel.org/r/20190319235619.260832-4-surenb@google.com
Link: http://lkml.kernel.org/r/20190124211518.244221-5-surenb@google.com
Signed-off-by: Suren Baghdasaryan 
Acked-by: Johannes Weiner 
Cc: Dennis Zhou 
Cc: Ingo Molnar 
Cc: Jens Axboe 
Cc: Li Zefan 
Cc: Peter Zijlstra 
Cc: Tejun Heo 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

psi: make psi_enable static

2019-05-15T02:52:47+00:00

psi_enable is not used outside of psi.c, make it static.

Link: http://lkml.kernel.org/r/20190319235619.260832-3-surenb@google.com
Signed-off-by: Suren Baghdasaryan 
Suggested-by: Andrew Morton 
Acked-by: Johannes Weiner 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds