user/sven/linux.git/kernel/sched/debug.c, branch v5.4.140

sched/debug: Fix cgroup_path[] serialization

2021-05-14T07:44:26Z

[ Upstream commit ad789f84c9a145f8a18744c0387cec22ec51651e ] The handling of sysrq key can be activated by echoing the key to /proc/sysrq-trigger or via the magic key sequence typed into a terminal that is connected to the system in some way (serial, USB or other mean). In the former case, the handling is done in a user context. In the latter case, it is likely to be in an interrupt context. Currently in print_cpu() of kernel/sched/debug.c, sched_debug_lock is taken with interrupt disabled for the whole duration of the calls to print_*_stats() and print_rq() which could last for the quite some time if the information dump happens on the serial console. If the system has many cpus and the sched_debug_lock is somehow busy (e.g. parallel sysrq-t), the system may hit a hard lockup panic depending on the actually serial console implementation of the system. The purpose of sched_debug_lock is to serialize the use of the global cgroup_path[] buffer in print_cpu(). The rests of the printk calls don't need serialization from sched_debug_lock. Calling printk() with interrupt disabled can still be problematic if multiple instances are running. Allocating a stack buffer of PATH_MAX bytes is not feasible because of the limited size of the kernel stack. The solution implemented in this patch is to allow only one caller at a time to use the full size group_path[], while other simultaneous callers will have to use shorter stack buffers with the possibility of path name truncation. A "..." suffix will be printed if truncation may have happened. The cgroup path name is provided for informational purpose only, so occasional path name truncation should not be a big problem. Fixes: efe25c2c7b3a ("sched: Reinstate group names in /proc/sched_debug") Suggested-by: Peter Zijlstra Signed-off-by: Waiman Long Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20210415195426.6677-1-longman@redhat.com Signed-off-by: Sasha Levin

sched/debug: Make sd->flags sysctl read-only

2020-07-09T07:37:50Z

[ Upstream commit 9818427c6270a9ce8c52c8621026fe9cebae0f92 ] Writing to the sysctl of a sched_domain->flags directly updates the value of the field, and goes nowhere near update_top_cache_domain(). This means that the cached domain pointers can end up containing stale data (e.g. the domain pointed to doesn't have the relevant flag set anymore). Explicit domain walks that check for flags will be affected by the write, but this won't be in sync with the cached pointers which will still point to the domains that were cached at the last sched_domain build. In other words, writing to this interface is playing a dangerous game. It could be made to trigger an update of the cached sched_domain pointers when written to, but this does not seem to be worth the trouble. Make it read-only. Signed-off-by: Valentin Schneider Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20200415210512.805-3-valentin.schneider@arm.com Signed-off-by: Sasha Levin

Merge tag 'v5.2-rc6' into sched/core, to refresh the branch

2019-06-24T17:19:53Z

Signed-off-by: Ingo Molnar

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500

2019-06-19T15:09:55Z

Based on 2 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation # extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 4122 file(s). Signed-off-by: Thomas Gleixner Reviewed-by: Enrico Weigelt Reviewed-by: Kate Stewart Reviewed-by: Allison Randal Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de Signed-off-by: Greg Kroah-Hartman

sched/core: Remove sd->*_idx

2019-06-03T09:49:40Z

The sched domain per rq load index files also disappear from the /proc/sys/kernel/sched_domain/cpuX/domainY directories. Signed-off-by: Dietmar Eggemann Signed-off-by: Peter Zijlstra (Intel) Acked-by: Rik van Riel Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Morten Rasmussen Cc: Patrick Bellasi Cc: Peter Zijlstra Cc: Quentin Perret Cc: Thomas Gleixner Cc: Valentin Schneider Cc: Vincent Guittot Link: https://lkml.kernel.org/r/20190527062116.11512-6-dietmar.eggemann@arm.com Signed-off-by: Ingo Molnar

sched/core: Remove rq->cpu_load[]

2019-06-03T09:49:40Z

The per rq load array values also disappear from the cpu#X sections in /proc/sched_debug. Signed-off-by: Dietmar Eggemann Signed-off-by: Peter Zijlstra (Intel) Acked-by: Rik van Riel Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Morten Rasmussen Cc: Patrick Bellasi Cc: Peter Zijlstra Cc: Quentin Perret Cc: Thomas Gleixner Cc: Valentin Schneider Cc: Vincent Guittot Link: https://lkml.kernel.org/r/20190527062116.11512-5-dietmar.eggemann@arm.com Signed-off-by: Ingo Molnar

sched/debug: Remove sd->*_idx range on sysctl

2019-06-03T09:49:39Z

This reverts: commit 201c373e8e48 ("sched/debug: Limit sd->*_idx range on sysctl") Load indexes (sd->*_idx) are no longer needed without rq->cpu_load[]. The range check for load indexes can be removed as well. Get rid of it before the rq->cpu_load[] since it uses CPU_LOAD_IDX_MAX. At the same time, fix the following coding style issues detected by scripts/checkpatch.pl: ERROR: space prohibited before that ',' ERROR: space prohibited before that close parenthesis ')' Signed-off-by: Dietmar Eggemann Signed-off-by: Peter Zijlstra (Intel) Acked-by: Rik van Riel Cc: Frederic Weisbecker Cc: Linus Torvalds Cc: Morten Rasmussen Cc: Patrick Bellasi Cc: Peter Zijlstra Cc: Quentin Perret Cc: Thomas Gleixner Cc: Valentin Schneider Cc: Vincent Guittot Link: https://lkml.kernel.org/r/20190527062116.11512-4-dietmar.eggemann@arm.com Signed-off-by: Ingo Molnar

sched/fair: Remove rq->load

2019-06-03T09:49:37Z

The CFS class is the only one maintaining and using the CPU wide load (rq->load(.weight)). The last use case of the CPU wide load in CFS's set_next_entity() can be replaced by using the load of the CFS class (rq->cfs.load(.weight)) instead. Signed-off-by: Dietmar Eggemann Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20190424084556.604-1-dietmar.eggemann@arm.com Signed-off-by: Ingo Molnar

sched/debug: Fix spelling mistake "logaritmic" -> "logarithmic"

2019-04-19T19:04:49Z

Signed-off-by: Colin Ian King Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: kernel-janitors@vger.kernel.org Link: http://lkml.kernel.org/r/20181128152350.13622-1-colin.king@canonical.com Signed-off-by: Ingo Molnar

sched/debug: Initialize sd_sysctl_cpus if !CONFIG_CPUMASK_OFFSTACK

2019-02-04T08:13:21Z

register_sched_domain_sysctl() copies the cpu_possible_mask into sd_sysctl_cpus, but only if sd_sysctl_cpus hasn't already been allocated (ie, CONFIG_CPUMASK_OFFSTACK is set). However, when CONFIG_CPUMASK_OFFSTACK is not set, sd_sysctl_cpus is left uninitialized (all zeroes) and the kernel may fail to initialize sched_domain sysctl entries for all possible CPUs. This is visible to the user if the kernel is booted with maxcpus=n, or if ACPI tables have been modified to leave CPUs offline, and then checking for missing /proc/sys/kernel/sched_domain/cpu* entries. Fix this by separating the allocation and initialization, and adding a flag to initialize the possible CPU entries while system booting only. Tested-by: Syuuichirou Ishii Tested-by: Tarumizu, Kohei Signed-off-by: Hidetoshi Seto Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Masayoshi Mizuma Acked-by: Joe Lawrence Cc: Linus Torvalds Cc: Masayoshi Mizuma Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Link: https://lkml.kernel.org/r/20190129151245.5073-1-msys.mizuma@gmail.com Signed-off-by: Ingo Molnar