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Date: Thu, 20 Sep 2012 08:25:01 +0530 From: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> To: David Rientjes <rientjes@...gle.com> CC: Konrad Rzeszutek Wilk <konrad@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>, Dave Jones <davej@...hat.com>, Linux Kernel <linux-kernel@...r.kernel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>, Suzuki Poulose <suzuki@...ibm.com> Subject: Re: 3.6rc6 slab corruption. On 09/20/2012 08:16 AM, David Rientjes wrote: > On Thu, 20 Sep 2012, Raghavendra K T wrote: > >> Only problem, I find is histogram data expands dynamically (because it >> changes). I think having static allocation of 352 bytes as suggested >> Linus is a good idea. >> > > Certainly, but it's a different topic and would be a subsequent patch to > either my patch or Konrad's patch. Before that's done, I think we should > fix the race condition that currently exists either by: > > - merging my patch (which I can sign-off and write a changelog for if > Konrad agrees), or > > - merging Konrad's patch and introducing a mutex so that it's possible to > do many reads to collect statistics after opening the file a single > time with a single fd. > > Since these files are incapable of doing lseek, it would seem that my > patch would be best and you'd simply want to close() + open() to read new > data, which also guarantees that all readers get the same information. > The only reason I hesitate on that and will defer to Konrad's opinion is > because the way the code is currently written looks like it was intended > to copy the data are read() rather than open(); in other words, it almost > seems as if they were made to be non-seekable after the u32_array_read() > implementation was complete and it was at one time possible to do an > lseek(SEEK_SET). Yes. common use case is just open once,read and close. i.e. cat /sys/kernel/debug/../histoblocked I also don't see why we have to keep fd open to read it. But yes let Konrad comment on that. > After that's fixed, and to address your concern, we can simply do the > allocation of file->private_data for the maximum size possible when the > file is created as a follow-up patch. I agree, missed that once we do a open and then read it we are done. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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