linux/drivers/pci
Rafael J. Wysocki c125e96f04 PM: Make it possible to avoid races between wakeup and system sleep
One of the arguments during the suspend blockers discussion was that
the mainline kernel didn't contain any mechanisms making it possible
to avoid races between wakeup and system suspend.

Generally, there are two problems in that area.  First, if a wakeup
event occurs exactly when /sys/power/state is being written to, it
may be delivered to user space right before the freezer kicks in, so
the user space consumer of the event may not be able to process it
before the system is suspended.  Second, if a wakeup event occurs
after user space has been frozen, it is not generally guaranteed that
the ongoing transition of the system into a sleep state will be
aborted.

To address these issues introduce a new global sysfs attribute,
/sys/power/wakeup_count, associated with a running counter of wakeup
events and three helper functions, pm_stay_awake(), pm_relax(), and
pm_wakeup_event(), that may be used by kernel subsystems to control
the behavior of this attribute and to request the PM core to abort
system transitions into a sleep state already in progress.

The /sys/power/wakeup_count file may be read from or written to by
user space.  Reads will always succeed (unless interrupted by a
signal) and return the current value of the wakeup events counter.
Writes, however, will only succeed if the written number is equal to
the current value of the wakeup events counter.  If a write is
successful, it will cause the kernel to save the current value of the
wakeup events counter and to abort the subsequent system transition
into a sleep state if any wakeup events are reported after the write
has returned.

[The assumption is that before writing to /sys/power/state user space
will first read from /sys/power/wakeup_count.  Next, user space
consumers of wakeup events will have a chance to acknowledge or
veto the upcoming system transition to a sleep state.  Finally, if
the transition is allowed to proceed, /sys/power/wakeup_count will
be written to and if that succeeds, /sys/power/state will be written
to as well.  Still, if any wakeup events are reported to the PM core
by kernel subsystems after that point, the transition will be
aborted.]

Additionally, put a wakeup events counter into struct dev_pm_info and
make these per-device wakeup event counters available via sysfs,
so that it's possible to check the activity of various wakeup event
sources within the kernel.

To illustrate how subsystems can use pm_wakeup_event(), make the
low-level PCI runtime PM wakeup-handling code use it.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Acked-by: Greg Kroah-Hartman <gregkh@suse.de>
Acked-by: markgross <markgross@thegnar.org>
Reviewed-by: Alan Stern <stern@rowland.harvard.edu>
2010-07-19 01:58:48 +02:00
..
hotplug PCI: hotplug/cpqphp, fix NULL dereference 2010-06-11 13:10:21 -07:00
pcie PM: Make it possible to avoid races between wakeup and system sleep 2010-07-19 01:58:48 +02:00
.gitignore
access.c PCI: output FW warning in pci_read/write_vpd 2010-05-18 15:00:25 -07:00
bus.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
dmar.c Merge git://git.infradead.org/iommu-2.6 2010-05-21 17:25:01 -07:00
hotplug-pci.c PCI: fix section mismatch warning in pci_scan_child_bus 2008-03-04 15:07:03 -08:00
hotplug.c Driver core: change add_uevent_var to use a struct 2007-10-12 14:51:01 -07:00
htirq.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
intel-iommu.c intel-iommu: Force-disable IOMMU for iGFX on broken Cantiga revisions. 2010-06-15 10:57:57 +01:00
intr_remapping.c Merge git://git.infradead.org/iommu-2.6 2010-05-21 17:25:01 -07:00
intr_remapping.h intr-remap: generic support for remapping HPET MSIs 2009-08-27 23:33:20 +02:00
ioapic.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
iov.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
iova.c intel-iommu: Remove superfluous iova_alloc_lock from IOVA code 2009-07-15 08:17:02 +01:00
irq.c PCI: struct device - replace bus_id with dev_name(), dev_set_name() 2009-01-07 11:12:23 -08:00
Kconfig PCI: change PCI_MSI help text to recommend enabling 2010-05-11 12:01:10 -07:00
Makefile microblaze: Enable PCI, missing files 2010-03-11 14:04:27 +01:00
msi.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
msi.h PCI MSI: shorten PCI_MSIX_ENTRY_* symbol names 2009-06-29 12:15:19 -07:00
pci-acpi.c PM: Make it possible to avoid races between wakeup and system sleep 2010-07-19 01:58:48 +02:00
pci-driver.c PCI PM: Run-time callbacks for PCI bus type 2010-02-22 16:21:19 -08:00
pci-stub.c PCI: pci-stub: add pci_stub.ids parameter 2009-09-09 13:44:34 -07:00
pci-sysfs.c Revert "PCI: create function symlinks in /sys/bus/pci/slots/N/" 2010-06-11 13:08:37 -07:00
pci.c PM: Make it possible to avoid races between wakeup and system sleep 2010-07-19 01:58:48 +02:00
pci.h PM: Make it possible to avoid races between wakeup and system sleep 2010-07-19 01:58:48 +02:00
probe.c ACPI, APEI, PCIE AER, use general HEST table parsing in AER firmware_first setup 2010-05-19 22:40:14 -04:00
proc.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
quirks.c ahci: add pci quirk for JMB362 2010-06-07 16:03:10 -04:00
remove.c PCI: eliminate redundant pci_stop_dev() call from pci_destroy_dev() 2009-06-11 12:04:19 -07:00
rom.c PCI: fix rom.c kernel-doc warning 2009-02-13 12:01:56 -08:00
search.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
setup-bus.c Revert "PCI: update bridge resources to get more big ranges in PCI assign unssigned" 2010-05-12 18:39:45 -07:00
setup-irq.c PCI: use dev_printk when possible 2008-06-25 16:05:13 -07:00
setup-res.c PCI: fall back to original BIOS BAR addresses 2010-07-16 11:39:48 -07:00
slot.c Revert "PCI: create function symlinks in /sys/bus/pci/slots/N/" 2010-06-11 13:08:37 -07:00
syscall.c headers: smp_lock.h redux 2009-07-12 12:22:34 -07:00
vpd.c pci: Add helper to search for VPD keywords 2010-02-28 00:43:33 -08:00