user/sven/linux.git/kernel/power/main.c, branch v6.1.116

freezer,sched: Rewrite core freezer logic

2022-09-07T19:53:50Z

Rewrite the core freezer to behave better wrt thawing and be simpler in general. By replacing PF_FROZEN with TASK_FROZEN, a special block state, it is ensured frozen tasks stay frozen until thawed and don't randomly wake up early, as is currently possible. As such, it does away with PF_FROZEN and PF_FREEZER_SKIP, freeing up two PF_flags (yay!). Specifically; the current scheme works a little like: freezer_do_not_count(); schedule(); freezer_count(); And either the task is blocked, or it lands in try_to_freezer() through freezer_count(). Now, when it is blocked, the freezer considers it frozen and continues. However, on thawing, once pm_freezing is cleared, freezer_count() stops working, and any random/spurious wakeup will let a task run before its time. That is, thawing tries to thaw things in explicit order; kernel threads and workqueues before doing bringing SMP back before userspace etc.. However due to the above mentioned races it is entirely possible for userspace tasks to thaw (by accident) before SMP is back. This can be a fatal problem in asymmetric ISA architectures (eg ARMv9) where the userspace task requires a special CPU to run. As said; replace this with a special task state TASK_FROZEN and add the following state transitions: TASK_FREEZABLE -> TASK_FROZEN __TASK_STOPPED -> TASK_FROZEN __TASK_TRACED -> TASK_FROZEN The new TASK_FREEZABLE can be set on any state part of TASK_NORMAL (IOW. TASK_INTERRUPTIBLE and TASK_UNINTERRUPTIBLE) -- any such state is already required to deal with spurious wakeups and the freezer causes one such when thawing the task (since the original state is lost). The special __TASK_{STOPPED,TRACED} states *can* be restored since their canonical state is in ->jobctl. With this, frozen tasks need an explicit TASK_FROZEN wakeup and are free of undue (early / spurious) wakeups. Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Ingo Molnar Acked-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/20220822114649.055452969@infradead.org

freezer: Have {,un}lock_system_sleep() save/restore flags

2022-09-07T19:53:48Z

Rafael explained that the reason for having both PF_NOFREEZE and PF_FREEZER_SKIP is that {,un}lock_system_sleep() is callable from kthread context that has previously called set_freezable(). In preparation of merging the flags, have {,un}lock_system_slee() save and restore current->flags. Signed-off-by: Peter Zijlstra (Intel) Acked-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/20220822114648.725003428@infradead.org

Merge tag 'cxl-for-5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl

2022-05-28T04:24:19Z

Pull cxl updates from Dan Williams: "Compute Express Link (CXL) updates for this cycle. The highlight is new driver-core infrastructure and CXL subsystem changes for allowing lockdep to validate device_lock() usage. Thanks to PeterZ for setting me straight on the current capabilities of the lockdep API, and Greg acked it as well. On the CXL ACPI side this update adds support for CXL _OSC so that platform firmware knows that it is safe to still grant Linux native control of PCIe hotplug and error handling in the presence of CXL devices. A circular dependency problem was discovered between suspend and CXL memory for cases where the suspend image might be stored in CXL memory where that image also contains the PCI register state to restore to re-enable the device. Disable suspend for now until an architecture is defined to clarify that conflict. Lastly a collection of reworks, fixes, and cleanups to the CXL subsystem where support for snooping mailbox commands and properly handling the "mem_enable" flow are the highlights. Summary: - Add driver-core infrastructure for lockdep validation of device_lock(), and fixup a deadlock report that was previously hidden behind the 'lockdep no validate' policy. - Add CXL _OSC support for claiming native control of CXL hotplug and error handling. - Disable suspend in the presence of CXL memory unless and until a protocol is identified for restoring PCI device context from memory hosted on CXL PCI devices. - Add support for snooping CXL mailbox commands to protect against inopportune changes, like set-partition with the 'immediate' flag set. - Rework how the driver detects legacy CXL 1.1 configurations (CXL DVSEC / 'mem_enable') before enabling new CXL 2.0 decode configurations (CXL HDM Capability). - Miscellaneous cleanups and fixes from -next exposure" * tag 'cxl-for-5.19' of git://git.kernel.org/pub/scm/linux/kernel/git/cxl/cxl: (47 commits) cxl/port: Enable HDM Capability after validating DVSEC Ranges cxl/port: Reuse 'struct cxl_hdm' context for hdm init cxl/port: Move endpoint HDM Decoder Capability init to port driver cxl/pci: Drop @info argument to cxl_hdm_decode_init() cxl/mem: Merge cxl_dvsec_ranges() and cxl_hdm_decode_init() cxl/mem: Skip range enumeration if mem_enable clear cxl/mem: Consolidate CXL DVSEC Range enumeration in the core cxl/pci: Move cxl_await_media_ready() to the core cxl/mem: Validate port connectivity before dvsec ranges cxl/mem: Fix cxl_mem_probe() error exit cxl/pci: Drop wait_for_valid() from cxl_await_media_ready() cxl/pci: Consolidate wait_for_media() and wait_for_media_ready() cxl/mem: Drop mem_enabled check from wait_for_media() nvdimm: Fix firmware activation deadlock scenarios device-core: Kill the lockdep_mutex nvdimm: Drop nd_device_lock() ACPI: NFIT: Drop nfit_device_lock() nvdimm: Replace lockdep_mutex with local lock classes cxl: Drop cxl_device_lock() cxl/acpi: Add root device lockdep validation ...

PM: CXL: Disable suspend

2022-04-22T23:09:42Z

The CXL specification claims S3 support at a hardware level, but at a system software level there are some missing pieces. Section 9.4 (CXL 2.0) rightly claims that "CXL mem adapters may need aux power to retain memory context across S3", but there is no enumeration mechanism for the OS to determine if a given adapter has that support. Moreover the save state and resume image for the system may inadvertantly end up in a CXL device that needs to be restored before the save state is recoverable. I.e. a circular dependency that is not resolvable without a third party save-area. Arrange for the cxl_mem driver to fail S3 attempts. This still nominaly allows for suspend, but requires unbinding all CXL memory devices before the suspend to ensure the typical DRAM flow is taken. The cxl_mem unbind flow is intended to also tear down all CXL memory regions associated with a given cxl_memdev. It is reasonable to assume that any device participating in a System RAM range published in the EFI memory map is covered by aux power and save-area outside the device itself. So this restriction can be minimized in the future once pre-existing region enumeration support arrives, and perhaps a spec update to clarify if the EFI memory map is sufficent for determining the range of devices managed by platform-firmware for S3 support. Per Rafael, if the CXL configuration prevents suspend then it should fail early before tasks are frozen, and mem_sleep should stop showing 'mem' as an option [1]. Effectively CXL augments the platform suspend ->valid() op since, for example, the ACPI ops are not aware of the CXL / PCI dependencies. Given the split role of platform firmware vs OS provisioned CXL memory it is up to the cxl_mem driver to determine if the CXL configuration has elements that platform firmware may not be prepared to restore. Link: https://lore.kernel.org/r/CAJZ5v0hGVN_=3iU8OLpHY3Ak35T5+JcBM-qs8SbojKrpd0VXsA@mail.gmail.com [1] Cc: "Rafael J. Wysocki" Cc: Pavel Machek Cc: Len Brown Reviewed-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/165066828317.3907920.5690432272182042556.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams

PM: sleep: enable dynamic debug support within pm_pr_dbg()

2022-04-13T14:34:01Z

Currently pm_pr_dbg() is used to filter kernel pm debug messages based on pm_debug_messages_on flag. The problem is if we enable/disable this flag it will affect all pm_pr_dbg() calls at once, so we can't individually control them. This patch changes pm_pr_dbg() implementation as such: - If pm_debug_messages_on is enabled, print the message. - If pm_debug_messages_on is disabled and CONFIG_DYNAMIC_DEBUG is enabled, only print the messages explicitly enabled on /sys/kernel/debug/dynamic_debug/control. - If pm_debug_messages_on is disabled and CONFIG_DYNAMIC_DEBUG is disabled, don't print the message. Signed-off-by: David Cohen Signed-off-by: Rafael J. Wysocki

PM: s2idle: ACPI: Fix wakeup interrupts handling

2022-02-07T20:02:31Z

After commit e3728b50cd9b ("ACPI: PM: s2idle: Avoid possible race related to the EC GPE") wakeup interrupts occurring immediately after the one discarded by acpi_s2idle_wake() may be missed. Moreover, if the SCI triggers again immediately after the rearming in acpi_s2idle_wake(), that wakeup may be missed too. The problem is that pm_system_irq_wakeup() only calls pm_system_wakeup() when pm_wakeup_irq is 0, but that's not the case any more after the interrupt causing acpi_s2idle_wake() to run until pm_wakeup_irq is cleared by the pm_wakeup_clear() call in s2idle_loop(). However, there may be wakeup interrupts occurring in that time frame and if that happens, they will be missed. To address that issue first move the clearing of pm_wakeup_irq to the point at which it is known that the interrupt causing acpi_s2idle_wake() to tun will be discarded, before rearming the SCI for wakeup. Moreover, because that only reduces the size of the time window in which the issue may manifest itself, allow pm_system_irq_wakeup() to register two second wakeup interrupts in a row and, when discarding the first one, replace it with the second one. [Of course, this assumes that only one wakeup interrupt can be discarded in one go, but currently that is the case and I am not aware of any plans to change that.] Fixes: e3728b50cd9b ("ACPI: PM: s2idle: Avoid possible race related to the EC GPE") Cc: 5.4+ # 5.4+ Signed-off-by: Rafael J. Wysocki

PM: sleep: unmark 'state' functions as kernel-doc

2021-08-16T16:49:39Z

Fix kernel-doc warnings in kernel/power/main.c by unmarking the comment block as kernel-doc notation. This eliminates the following kernel-doc warnings: kernel/power/main.c:593: warning: expecting prototype for state(). Prototype was for state_show() instead kernel/power/main.c:593: warning: Function parameter or member 'kobj' not described in 'state_show' kernel/power/main.c:593: warning: Function parameter or member 'attr' not described in 'state_show' kernel/power/main.c:593: warning: Function parameter or member 'buf' not described in 'state_show' Signed-off-by: Randy Dunlap Signed-off-by: Rafael J. Wysocki

PM: sleep: Constify static struct attribute_group

2021-02-12T15:46:59Z

The only usage of suspend_attr_group is to put its address in an array of pointers to const attribute_group structs. Make it const to allow the compiler to put it into read-only memory. Signed-off-by: Rikard Falkeborn Signed-off-by: Rafael J. Wysocki

notifier: Fix broken error handling pattern

2020-09-01T07:58:03Z

The current notifiers have the following error handling pattern all over the place: int err, nr; err = __foo_notifier_call_chain(&chain, val_up, v, -1, &nr); if (err & NOTIFIER_STOP_MASK) __foo_notifier_call_chain(&chain, val_down, v, nr-1, NULL) And aside from the endless repetition thereof, it is broken. Consider blocking notifiers; both calls take and drop the rwsem, this means that the notifier list can change in between the two calls, making @nr meaningless. Fix this by replacing all the __foo_notifier_call_chain() functions with foo_notifier_call_chain_robust() that embeds the above pattern, but ensures it is inside a single lock region. Note: I switched atomic_notifier_call_chain_robust() to use the spinlock, since RCU cannot provide the guarantee required for the recovery. Note: software_resume() error handling was broken afaict. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Acked-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/20200818135804.325626653@infradead.org

PM: sleep: Add pm_debug_messages kernel command line option

2020-04-02T13:29:56Z

Debug messages from the system suspend/hibernation infrastructure are disabled by default, and can only be enabled after the system has boot up via /sys/power/pm_debug_messages. This makes the hibernation resume hard to track as it involves system boot up across hibernation. There's no chance for software_resume() to track the resume process, for example. Add a kernel command line option to set pm_debug_messages during boot up. Signed-off-by: Chen Yu [ rjw: Subject & changelog ] Signed-off-by: Rafael J. Wysocki