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Filename Latest commit message Latest commit date
Thomas Pfaff ac5894fb86 genirq: Synchronize interrupt thread startup 
commit 8707898e22fd665bc1d7b18b809be4b56ce25bdd upstream.

A kernel hang can be observed when running setserial in a loop on a kernel
with force threaded interrupts. The sequence of events is:

   setserial
     open("/dev/ttyXXX")
       request_irq()
     do_stuff()
      -> serial interrupt
         -> wake(irq_thread)
	      desc->threads_active++;
     close()
       free_irq()
         kthread_stop(irq_thread)
     synchronize_irq() <- hangs because desc->threads_active != 0

The thread is created in request_irq() and woken up, but does not get on a
CPU to reach the actual thread function, which would handle the pending
wake-up. kthread_stop() sets the should stop condition which makes the
thread immediately exit, which in turn leaves the stale threads_active
count around.

This problem was introduced with commit 519cc8652b, which addressed a
interrupt sharing issue in the PCIe code.

Before that commit free_irq() invoked synchronize_irq(), which waits for
the hard interrupt handler and also for associated threads to complete.

To address the PCIe issue synchronize_irq() was replaced with
__synchronize_hardirq(), which only waits for the hard interrupt handler to
complete, but not for threaded handlers.

This was done under the assumption, that the interrupt thread already
reached the thread function and waits for a wake-up, which is guaranteed to
be handled before acting on the stop condition. The problematic case, that
the thread would not reach the thread function, was obviously overlooked.

Make sure that the interrupt thread is really started and reaches
thread_fn() before returning from __setup_irq().

This utilizes the existing wait queue in the interrupt descriptor. The
wait queue is unused for non-shared interrupts. For shared interrupts the
usage might cause a spurious wake-up of a waiter in synchronize_irq() or the
completion of a threaded handler might cause a spurious wake-up of the
waiter for the ready flag. Both are harmless and have no functional impact.

[ tglx: Amended changelog ]

Fixes: 519cc8652b ("genirq: Synchronize only with single thread on free_irq()")
Signed-off-by: Thomas Pfaff <tpfaff@pcs.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/552fe7b4-9224-b183-bb87-a8f36d335690@pcs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-05-12 12:23:41 +02:00
arch parisc: Merge model and model name into one line in /proc/cpuinfo 2022-05-12 12:23:40 +02:00
block block/compat_ioctl: fix range check in BLKGETSIZE 2022-04-27 13:50:50 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:47:29 +02:00
crypto crypto: authenc - Fix sleep in atomic context in decrypt_tail 2022-04-15 14:18:04 +02:00
Documentation ext4, doc: fix incorrect h_reserved size 2022-04-27 13:50:50 +02:00
drivers ACPICA: Always create namespace nodes using acpi_ns_create_node() 2022-05-12 12:23:41 +02:00
fs mm, hugetlb: allow for "high" userspace addresses 2022-05-09 09:03:28 +02:00
include mm, hugetlb: allow for "high" userspace addresses 2022-05-09 09:03:28 +02:00
init init/main.c: return 1 from handled __setup() functions 2022-04-15 14:18:35 +02:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:23:35 +01:00
kernel genirq: Synchronize interrupt thread startup 2022-05-12 12:23:41 +02:00
lib hex2bin: fix access beyond string end 2022-05-09 09:03:22 +02:00
LICENSES
mm mm, hugetlb: allow for "high" userspace addresses 2022-05-09 09:03:28 +02:00
net Revert "SUNRPC: attempt AF_LOCAL connect on setup" 2022-05-12 12:23:40 +02:00
samples samples/kretprobes: Fix return value if register_kretprobe() failed 2021-11-17 09:48:39 +01:00
scripts gcc-plugins: latent_entropy: use /dev/urandom 2022-04-20 09:19:38 +02:00
security Fix incorrect type in assignment of ipv6 port for audit 2022-04-15 14:18:22 +02:00
sound ALSA: fireworks: fix wrong return count shorter than expected by 4 bytes 2022-05-12 12:23:40 +02:00
tools selftests: mlxsw: vxlan_flooding: Prevent flooding of unwanted packets 2022-04-27 13:50:47 +02:00
usr
virt KVM: Prevent module exit until all VMs are freed 2022-04-15 14:18:27 +02:00
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Makefile Linux 5.4.192 2022-05-09 09:03:28 +02:00
README

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.

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.