Revision c492e2d464c82fdb82002569033325b4e1a7e5eb authored by Linus Torvalds on 29 May 2015, 17:35:21 UTC, committed by Linus Torvalds on 29 May 2015, 17:35:21 UTC
Pull m,ore md bugfixes gfrom Neil Brown: "Assorted fixes for new RAID5 stripe-batching functionality. Unfortunately this functionality was merged a little prematurely. The necessary testing and code review is now complete (or as complete as it can be) and to code passes a variety of tests and looks quite sensible. Also a fix for some recent locking changes - a race was introduced which causes a reshape request to sometimes fail. No data safety issues" * tag 'md/4.1-rc5-fixes' of git://neil.brown.name/md: md: fix race when unfreezing sync_action md/raid5: break stripe-batches when the array has failed. md/raid5: call break_stripe_batch_list from handle_stripe_clean_event md/raid5: be more selective about distributing flags across batch. md/raid5: add handle_flags arg to break_stripe_batch_list. md/raid5: duplicate some more handle_stripe_clean_event code in break_stripe_batch_list md/raid5: remove condition test from check_break_stripe_batch_list. md/raid5: Ensure a batch member is not handled prematurely. md/raid5: close race between STRIPE_BIT_DELAY and batching. md/raid5: ensure whole batch is delayed for all required bitmap updates.
irqflags-tracing.txt
IRQ-flags state tracing
started by Ingo Molnar <mingo@redhat.com>
the "irq-flags tracing" feature "traces" hardirq and softirq state, in
that it gives interested subsystems an opportunity to be notified of
every hardirqs-off/hardirqs-on, softirqs-off/softirqs-on event that
happens in the kernel.
CONFIG_TRACE_IRQFLAGS_SUPPORT is needed for CONFIG_PROVE_SPIN_LOCKING
and CONFIG_PROVE_RW_LOCKING to be offered by the generic lock debugging
code. Otherwise only CONFIG_PROVE_MUTEX_LOCKING and
CONFIG_PROVE_RWSEM_LOCKING will be offered on an architecture - these
are locking APIs that are not used in IRQ context. (the one exception
for rwsems is worked around)
architecture support for this is certainly not in the "trivial"
category, because lots of lowlevel assembly code deal with irq-flags
state changes. But an architecture can be irq-flags-tracing enabled in a
rather straightforward and risk-free manner.
Architectures that want to support this need to do a couple of
code-organizational changes first:
- add and enable TRACE_IRQFLAGS_SUPPORT in their arch level Kconfig file
and then a couple of functional changes are needed as well to implement
irq-flags-tracing support:
- in lowlevel entry code add (build-conditional) calls to the
trace_hardirqs_off()/trace_hardirqs_on() functions. The lock validator
closely guards whether the 'real' irq-flags matches the 'virtual'
irq-flags state, and complains loudly (and turns itself off) if the
two do not match. Usually most of the time for arch support for
irq-flags-tracing is spent in this state: look at the lockdep
complaint, try to figure out the assembly code we did not cover yet,
fix and repeat. Once the system has booted up and works without a
lockdep complaint in the irq-flags-tracing functions arch support is
complete.
- if the architecture has non-maskable interrupts then those need to be
excluded from the irq-tracing [and lock validation] mechanism via
lockdep_off()/lockdep_on().
in general there is no risk from having an incomplete irq-flags-tracing
implementation in an architecture: lockdep will detect that and will
turn itself off. I.e. the lock validator will still be reliable. There
should be no crashes due to irq-tracing bugs. (except if the assembly
changes break other code by modifying conditions or registers that
shouldn't be)
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