Messages in this thread | | | Date | Mon, 21 Aug 2006 15:48:41 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH] sys_ioprio_set: don't disable irqs |
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On Mon, 21 Aug 2006 00:50:34 +0400 Oleg Nesterov <oleg@tv-sign.ru> wrote:
> Question: why do we need to disable irqs in exit_io_context() ?
iirc it was to prevent IRQ-context code from getting a hold on current->io_context and then playing around with it while it's getting freed.
In practice, a preempt_disable() there would probably suffice (ie: if this CPU is running an ISR, it won't be running exit_io_context as well). But local_irq_disable() is clearer, albeit more expensive.
> Why do we need ->alloc_lock to clear io_context->task ?
To prevent races against elv_unregister(), I guess.
> In other words, could you explain why the patch below is not correct. > > Thanks, > > Oleg. > > --- 2.6.18-rc4/block/ll_rw_blk.c~6_exit 2006-08-20 19:30:10.000000000 +0400 > +++ 2.6.18-rc4/block/ll_rw_blk.c 2006-08-20 22:34:46.000000000 +0400 > @@ -3580,25 +3580,22 @@ EXPORT_SYMBOL(put_io_context); > /* Called by the exitting task */ > void exit_io_context(void) > { > - unsigned long flags; > struct io_context *ioc; > struct cfq_io_context *cic; > > - local_irq_save(flags); > task_lock(current); > ioc = current->io_context; > current->io_context = NULL; > - ioc->task = NULL; > task_unlock(current); > - local_irq_restore(flags); > > + ioc->task = NULL; > if (ioc->aic && ioc->aic->exit) > ioc->aic->exit(ioc->aic); > if (ioc->cic_root.rb_node != NULL) { > cic = rb_entry(rb_first(&ioc->cic_root), struct cfq_io_context, rb_node); > cic->exit(ioc); > } > - > + > put_io_context(ioc); > } > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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