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List:       linux-raid
Subject:    Does the md codes can work well under SMP?
From:       "liyiming" <liyiming () nrchpc ! ac ! cn>
Date:       2006-12-12 7:23:59
Message-ID: 200612121523597963092 () nrchpc ! ac ! cn
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These days I devoted to reading md codes in 2.6.12_r11
I have noticed that you applied two different locking strategy in these two functions:
end_read_request:
	if (uptodate) {
		set_bit(R5_UPTODATE, &sh->dev[i].flags);	
	} else {
		md_error(conf->mddev, conf->disks[i].rdev);
		clear_bit(R5_UPTODATE, &sh->dev[i].flags);
	}
	rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
	clear_bit(R5_LOCKED, &sh->dev[i].flags);
	set_bit(STRIPE_HANDLE, &sh->state);
	release_stripe(sh);
end_write_request:
	spin_lock_irqsave(&conf->device_lock, flags);
	if (!uptodate)
		md_error(conf->mddev, conf->disks[i].rdev);

	rdev_dec_pending(conf->disks[i].rdev, conf->mddev);
	
	clear_bit(R5_LOCKED, &sh->dev[i].flags);
	set_bit(STRIPE_HANDLE, &sh->state);
	__release_stripe(conf, sh);
	spin_unlock_irqrestore(&conf->device_lock, flags);


if these two function excuting on different CPU, the spin lock can work well? and why?
 				
--------------
liyiming
2006-12-12

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