linux-kernel - Re: decode GFP flags in oom killer output.

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Message-ID: <20120308000233.GA10695@redhat.com>
Date:	Wed, 7 Mar 2012 19:02:33 -0500
From:	Dave Jones <davej@...hat.com>
To:	Michal Nazarewicz <mina86@...a86.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: decode GFP flags in oom killer output.

On Thu, Mar 08, 2012 at 12:48:08AM +0100, Michal Nazarewicz wrote:
 
 > > +static void decode_gfp_mask(gfp_t gfp_mask, char *out_string)
 > > +{
 > > +	unsigned int i;
 > > +
 > > +	for (i = 0; i < 32; i++) {
 > > +		if (gfp_mask & (1 << i)) {
 > > +			if (gfp_flag_texts[i])
 > > +				out_string += sprintf(out_string, "%s ", gfp_flag_texts[i]);
 > > +			else
 > > +				out_string += sprintf(out_string, "reserved! ");
 > > +		}
 > > +	}
 > > +	out_string = "\0";
 > 
 > Uh?  Did you mean “*out_string = 0;” which is redundant anyway?

Yeah, that was the intent.
 
 > Also, this leaves a trailing space at the end of the string.

The zero was supposed to wipe it out, but I just realized it's advanced past it.
 
 > >  static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
 > >  			struct mem_cgroup *memcg, const nodemask_t *nodemask)
 > >  {
 > > +	char gfp_string[80];
 > 
 > For ~0, the string will be 256 characters followed by a NUL byte byte at the end.
 > This combination may make no sense, but the point is that you need to take length
 > of the buffer into account, probably by using snprintf() and a counter.

alternatively, we could just use a bigger buffer here.

thanks,

	Dave
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