Bug 194979

Summary: uart_intr leads to "bad stray interrupt" under pressure
Product: Base System Reporter: Max Laier <max.laier>
Component: kernAssignee: freebsd-bugs (Nobody) <bugs>
Status: Closed FIXED    
Severity: Affects Some People CC: cse.cem, harry.weppner, marcel, marius
Priority: ---    
Version: CURRENT   
Hardware: Any   
OS: Any   
Attachments:
Description Flags
Setup uart_intr() as both filter and hander none

Description Max Laier 2014-11-13 02:30:20 UTC 
Created attachment 149349 [details]
Setup uart_intr() as both filter and hander

Broken by:
https://svnweb.freebsd.org/base?view=revision&revision=253161

With this, uart_intr() can return FILTER_SCHEDULE_THREAD, but we don't setup a
threaded handler, which leads to the panic.

Since the handling in uart_intr() looks MP-safe now, the attached patch should
do the trick.
Comment 1 commit-hook freebsd_committer freebsd_triage 2015-07-24 17:02:18 UTC 
A commit references this bug:

Author: marius
Date: Fri Jul 24 17:01:18 UTC 2015
New revision: 285843
URL: https://svnweb.freebsd.org/changeset/base/285843

Log:
  - Since r253161, uart_intr() abuses FILTER_SCHEDULE_THREAD for signaling
    uart_bus_attach() during its test that 20 iterations weren't sufficient
    for clearing all pending interrupts, assuming this means that hardware
    is broken and doesn't deassert interrupts. However, under pressure, 20
    iterations also can be insufficient for clearing all pending interrupts,
    leading to a panic as intr_event_handle() tries to schedule an interrupt
    handler not registered. Solve this by introducing a flag that is set in
    test mode and otherwise restores pre-r253161 behavior of uart_intr(). The
    approach of additionally registering uart_intr() as handler as suggested
    in PR 194979 is not taken as that in turn would abuse special pccard and
    pccbb handling code of intr_event_handle(). [1]
  - Const'ify uart_driver_name.
  - Fix some minor style bugs.

  PR:		194979 [1]
  Reviewed by:	marcel (earlier version)
  MFC after:	3 days

Changes:
  head/sys/dev/uart/uart_bus.h
  head/sys/dev/uart/uart_core.c
Comment 2 commit-hook freebsd_committer freebsd_triage 2015-07-30 02:23:45 UTC 
A commit references this bug:

Author: marius
Date: Thu Jul 30 02:23:11 UTC 2015
New revision: 286059
URL: https://svnweb.freebsd.org/changeset/base/286059

Log:
  MFC: r285843

  - Since r253161, uart_intr() abuses FILTER_SCHEDULE_THREAD for signaling
    uart_bus_attach() during its test that 20 iterations weren't sufficient
    for clearing all pending interrupts, assuming this means that hardware
    is broken and doesn't deassert interrupts. However, under pressure, 20
    iterations also can be insufficient for clearing all pending interrupts,
    leading to a panic as intr_event_handle() tries to schedule an interrupt
    handler not registered. Solve this by introducing a flag that is set in
    test mode and otherwise restores pre-r253161 behavior of uart_intr(). The
    approach of additionally registering uart_intr() as handler as suggested
    in PR 194979 is not taken as that in turn would abuse special pccard and
    pccbb handling code of intr_event_handle(). [1]
  - Const'ify uart_driver_name.
  - Fix some minor style bugs.

  PR:		194979 [1]
  Reviewed by:	marcel (earlier version)

Changes:
_U  stable/10/
  stable/10/sys/dev/uart/uart_bus.h
  stable/10/sys/dev/uart/uart_core.c
Comment 3 commit-hook freebsd_committer freebsd_triage 2015-07-30 03:06:54 UTC 
A commit references this bug:

Author: marius
Date: Thu Jul 30 03:06:13 UTC 2015
New revision: 286061
URL: https://svnweb.freebsd.org/changeset/base/286061

Log:
  MFC: r285843 (r286059 in stable/10)

  - Since r253161, uart_intr() abuses FILTER_SCHEDULE_THREAD for signaling
    uart_bus_attach() during its test that 20 iterations weren't sufficient
    for clearing all pending interrupts, assuming this means that hardware
    is broken and doesn't deassert interrupts. However, under pressure, 20
    iterations also can be insufficient for clearing all pending interrupts,
    leading to a panic as intr_event_handle() tries to schedule an interrupt
    handler not registered. Solve this by introducing a flag that is set in
    test mode and otherwise restores pre-r253161 behavior of uart_intr(). The
    approach of additionally registering uart_intr() as handler as suggested
    in PR 194979 is not taken as that in turn would abuse special pccard and
    pccbb handling code of intr_event_handle(). [1]
  - Const'ify uart_driver_name.
  - Fix some minor style bugs.

  PR:		194979 [1]
  Reviewed by:	marcel (earlier version)
  Approved by:	re (gjb)

Changes:
_U  releng/10.2/
  releng/10.2/sys/dev/uart/uart_bus.h
  releng/10.2/sys/dev/uart/uart_core.c