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Thomas Gleixner 9fddc16ff6 x86/ioapic: Unbreak check_timer() commit `86a82ae0b5` upstream. Several people reported in the kernel bugzilla that between v4.12 and v4.13 the magic which works around broken hardware and BIOSes to find the proper timer interrupt delivery mode stopped working for some older affected platforms which need to fall back to ExtINT delivery mode. The reason is that the core code changed to keep track of the masked and disabled state of an interrupt line more accurately to avoid the expensive hardware operations. That broke an assumption in i8259_make_irq() which invokes disable_irq_nosync(); irq_set_chip_and_handler(); enable_irq(); Up to v4.12 this worked because enable_irq() unconditionally unmasked the interrupt line, but after the state tracking improvements this is not longer the case because the IO/APIC uses lazy disabling. So the line state is unmasked which means that enable_irq() does not call into the new irq chip to unmask it. In principle this is a shortcoming of the core code, but it's more than unclear whether the core code should try to reset state. At least this cannot be done unconditionally as that would break other existing use cases where the chip type is changed, e.g. when changing the trigger type, but the callers expect the state to be preserved. As the way how check_timer() is switching the delivery modes is truly unique, the obvious fix is to simply unmask the i8259 manually after changing the mode to ExtINT delivery and switching the irq chip to the legacy PIC. Note, that the fixes tag is not really precise, but identifies the commit which broke the assumptions in the IO/APIC and i8259 code and that's the kernel version to which this needs to be backported. Fixes: `bf22ff45be` ("genirq: Avoid unnecessary low level irq function calls") Reported-by: p_c_chan@hotmail.com Reported-by: ecm4@mail.com Reported-by: perdigao1@yahoo.com Reported-by: matzes@users.sourceforge.net Reported-by: rvelascog@gmail.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: p_c_chan@hotmail.com Tested-by: matzes@users.sourceforge.net Cc: stable@vger.kernel.org Link: https://bugzilla.kernel.org/show_bug.cgi?id=197769 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2020-10-01 13:14:25 +02:00
arch	x86/ioapic: Unbreak check_timer()	2020-10-01 13:14:25 +02:00
block	block: ensure bdi->io_pages is always initialized	2020-09-12 13:40:22 +02:00
certs	export.h: remove VMLINUX_SYMBOL() and VMLINUX_SYMBOL_STR()	2018-08-22 23:21:44 +09:00
crypto	crypto: af_alg - fix use-after-free in af_alg_accept() due to bh_lock_sock()	2020-07-09 09:37:10 +02:00
Documentation	kbuild: support LLVM=1 to switch the default tools to Clang/LLVM	2020-09-26 18:01:32 +02:00
drivers	media: smiapp: Fix error handling at NVM reading	2020-10-01 13:14:25 +02:00
firmware	Fix built-in early-load Intel microcode alignment	2020-01-23 08:21:29 +01:00
fs	f2fs: Return EOF on unaligned end of file DIO read	2020-09-23 12:10:59 +02:00
include	tcp_bbr: adapt cwnd based on ack aggregation estimation	2020-09-26 18:01:32 +02:00
init	printk: queue wake_up_klogd irq_work only if per-CPU areas are ready	2020-07-22 09:32:13 +02:00
ipc	ipc/util.c: sysvipc_find_ipc() incorrectly updates position index	2020-05-20 08:18:40 +02:00
kernel	kprobes: fix kill kprobe which has been marked as gone	2020-09-26 18:01:28 +02:00
lib	test_kmod: avoid potential double free in trigger_config_run_type()	2020-08-21 11:05:38 +02:00
LICENSES	LICENSES: Remove CC-BY-SA-4.0 license text	2018-10-18 11:28:50 +02:00
mm	mm: fix double page fault on arm64 if PTE_AF is cleared	2020-10-01 13:14:24 +02:00
net	tcp_bbr: adapt cwnd based on ack aggregation estimation	2020-09-26 18:01:32 +02:00
samples	samples: bpf: Fix build error	2020-06-03 08:19:31 +02:00
scripts	checkpatch: fix the usage of capture group ( ... )	2020-09-09 19:04:32 +02:00
security	selinux: allow labeling before policy is loaded	2020-10-01 13:14:23 +02:00
sound	ASoC: kirkwood: fix IRQ error handling	2020-10-01 13:14:24 +02:00
tools	kbuild: support LLVM=1 to switch the default tools to Clang/LLVM	2020-09-26 18:01:32 +02:00
usr	initramfs: restore default compression behavior	2020-04-13 10:44:59 +02:00
virt	KVM: fix memory leak in kvm_io_bus_unregister_dev()	2020-09-26 18:01:28 +02:00
.clang-format	clang-format: Set IndentWrappedFunctionNames false	2018-08-01 18:38:51 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes
.gitignore	Kbuild updates for v4.17 (2nd)	2018-04-15 17:21:30 -07:00
.mailmap	libnvdimm-for-4.19_misc	2018-08-25 18:13:10 -07:00
COPYING	COPYING: use the new text with points to the license files	2018-03-23 12:41:45 -06:00
CREDITS	9p: remove Ron Minnich from MAINTAINERS	2018-08-17 16:20:26 -07:00
Kbuild
Kconfig	kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt	2018-08-02 08:06:55 +09:00
MAINTAINERS	Documentation/llvm: add documentation on building w/ Clang/LLVM	2020-09-26 18:01:31 +02:00
Makefile	Linux 4.19.148	2020-09-26 18:01:33 +02:00
README	Docs: Added a pointer to the formatted docs to README	2018-03-21 09:02:53 -06:00

README

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.