7 Feb 2007 13:20
RE: Could "bio_vec" be referenced any time?
Yu-Chen Wu <g944370 <at> oz.nthu.edu.tw>
2007-02-07 12:20:42 GMT
2007-02-07 12:20:42 GMT
Hi NeilBrown, Thank you for your help and introducing "ksymoops" to me. I think you are right. The BIO is passed by MD put BIO into a share "kfifo". THX : ) -----Original Message----- From: linux-raid-owner <at> vger.kernel.org [mailto:linux-raid-owner <at> vger.kernel.org] On Behalf Of Neil Brown Sent: Wednesday, February 07, 2007 3:46 AM To: Yu-Chen Wu Cc: linux-kernel <at> vger.kernel.org; linux-raid <at> vger.kernel.org Subject: Re: Could "bio_vec" be referenced any time? On Tuesday February 6, g944370 <at> oz.nthu.edu.tw wrote: > Hi all, > I write a module that creates a kernel thread to show the BIOs from > MD modules. > The kernel thread will call show_bio() when md passing a BIO to my > module,else sleep. > Sometimes, show_bio() continues working successfully ,but it > somtimes makes "general protection fault". > The show_bio() always works when I comment the > "bio_for_each_segment" loop. > Is the zone I comment the cause of the fault? > As above, I consider it's the main problem.Also, I strongly want to > know your opinions.Thank you for help. > > THX Without seeing how the bio gets to show_bio it is hard to be certain, but my guess would be that by the time show_bio tries to inspect the bio, the IO request involving it has already completed and the bio has been freed, so you are accessing freed memory. > Feb 6 22:00:28 RAID-SUSE kernel: Code: 8b 00 f6 c4 08 74 0e 48 c7 c7 14 9c > 45 88 31 c0 e8 b5 bf e2 If you feed this line into ksymoops you get: Code; 0000000000000000 Before first symbol 0: 8b 00 mov (%rax),%eaxC ... so it is trying to dereference $rax. > Feb 6 22:00:28 RAID-SUSE kernel: RAX: 6b6b6b6b6b6b6b6b RBX: > ffff810037f52668 RCX: 0000000000040000 Which contains 6b6b6b6b6b6b6b6b. which is lots of copies of 'POISON_FREE' (defined in include/linux/poison.h) which makes it really look like that memory has already been freed. NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo <at> vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo <at> vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html