On Tue, 23 Jul 2002, Linus Torvalds wrote:
> /* BIG comment about what we're doing. */
> /* We're dropping the spinlock, but we remain non-preemptable */
> __raw_spin_unlock(..);
>
> and then later on, when preemptability is over, we do
>
> local_irq_enable();
> preempt_enable();
>
> so that we _clearly_ mark out the region where we must not re-schedule.
agreed, this is much nicer.
i removed the spin_unlock_no_resched() define, and modified the slab.c fix
(and the other spin_unlock_no_resched() places) to be more verbose about
what they do.
we still have preempt_enable_no_resched() - that is legitimately needed in
a number of cases - i've added comments to make its usage clear.
these cleanups are in the -G5 patch:
http://redhat.com/~mingo/remove-irqlock-patches/remove-irqlock-2.5.27-G5
i've test-booted BK-curr + G5, CONFIG_SMP, CONFIG_PREEMPT and
CONFIG_DEBUG_IRQ_SCHEDULE kernel on an SMP box, it works fine.
Ingo
Changes in -G3:
- slab.c needs to spin_unlock_no_resched(), instead of spin_unlock(). (It
also has to check for preemption in the right spot.) This should fix
the memory corruption.
- irq_exit() needs to run softirqs if interrupts not active - in the
previous patch it ran them when preempt_count() was 0, which is
incorrect.
- spinlock macros are updated to enable preemption after enabling
interrupts. Besides avoiding false positive warnings, this also
- fork.c has to call scheduler_tick() with preemption disabled -
otherwise scheduler_tick()'s spin_unlock can preempt!
- irqs_disabled() macro introduced.
- [ all other local_irq_enable() or sti instances conditional on
CONFIG_DEBUG_IRQ_SCHEDULE are to fix false positive warnings. ]
Changes in -G0:
- fix buggy in_softirq(). Fortunately the bug made the test broader,
which didnt result in algorithmical breakage, just suboptimal
performance.
- move do_softirq() processing into irq_exit() => this also fixes the
softirq processing bugs present in apic.c IRQ handlers that did not
test for softirqs after irq_exit().
- simplify local_bh_enable().
Changes in -F9:
- replace all instances of:
local_save_flags(flags);
local_irq_disable();
with the shorter form of:
local_irq_save(flags);
about 30 files are affected by this change.
Changes in -F8:
- preempt/hardirq/softirq count separation, cleanups.
- skbuff.c fix.
- use irq_count() in scheduler_tick()
Changes in -F3:
- the entry.S cleanups/speedups by Oleg Nesterov.
- a rather critical synchronize_irq() bugfix: if a driver frees an
interrupt that is still being probed then synchronize_irq() locks up.
This bug has caused a spurious boot-lockup on one of my testsystems,
ifconfig would lock up trying to close eth0.
- remove duplicate definitions from asm-i386/system.h, this fixes
compiler warnings.
-
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This archive was generated by hypermail 2b29 : Tue Jul 23 2002 - 22:00:45 EST