linux-kernel - RE: can a kmalloc be both GFP_ATOMIC and GFP

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Date:	Sat, 28 Apr 2007 08:03:42 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	"Robert P. J. Day" <rpjday@...dspring.com>
Cc:	"Shan, Guo Wen (Gavin)" <gshan@...atel-lucent.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: RE: can a kmalloc be both GFP_ATOMIC and GFP_KERNEL at the same
	time?


> >
> >
> >   i'd always assumed that the type flags of GFP_ATOMIC and GFP_KERNEL
> > were mutually exclusive when it came to calling kmalloc(), at least
> > based on everything i'd read.  so i'm not sure how to interpret the
> > following:
> >
> > drivers/scsi/aic7xxx_old.c:  aic_dev = kmalloc(sizeof(struct aic_dev_data), GFP_ATOMIC | GFP_KERNEL);
> > drivers/message/i2o/device.c:   resblk = kmalloc(buflen + 8, GFP_KERNEL | GFP_ATOMIC);
> >
> >   clarification?
> 
> oh, i'm *aware* of the definitions of those flags, but every single
> source i've ever read has *strongly* suggested that you don't use
> those two flags together so i was surprised to see those combinations.
> (as an example, love's kernel book, p. 192, shows a table of valid
> combinations of flags to use, but doesn't mention the one above.)
> 
> and, on the other hand, if they *are* legal to use together, i guess
> i'm kind of surprised that there would be only two instances of it.

it's not legal to use the combo; you have found yourself a very genuine
bug here! Good spotting!


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