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Date: Wed, 15 Nov 2006 10:20:43 -0800 From: Badari Pulavarty <pbadari@...ibm.com> To: Andrew Morton <akpm@...l.org> CC: linux-mm <linux-mm@...ck.org>, ext4 <linux-ext4@...r.kernel.org>, lkml <linux-kernel@...r.kernel.org> Subject: Re: pagefault in generic_file_buffered_write() causing deadlock Andrew Morton wrote: > On Wed, 15 Nov 2006 07:57:45 -0800 > Badari Pulavarty <pbadari@...ibm.com> wrote: > > >> We are looking at a customer situation (on 2.6.16-based distro) - where >> system becomes almost useless while running some java & stress tests. >> >> Root cause seems to be taking a pagefault in generic_file_buffered_write >> () after calling prepare_write. I am wondering >> >> 1) Why & How this can happen - since we made sure to fault the user >> buffer before prepare write. >> > > When using writev() we only fault in the first segment of the iovec. If > the second or succesive segment isn't mapped into pagetables we're > vulnerable to the deadlock. > > Hmm.. Not it :( Its coming from write() not writev(). [C00000002ABBF290] [C00000000039D58C] .do_page_fault+0x2e4/0x75c [C00000002ABBF460] [C000000000004860] .handle_page_fault+0x20/0x54 --- Exception: 301 at .__copy_tofrom_user+0x11c/0x580 LR = .generic_file_buffered_write+0x39c/0x7c8 [C00000002ABBF750] [C000000000095A94] .generic_file_buffered_write+0x2c0/0x7c8 ( unreliable) [C00000002ABBF8F0] [C0000000000962EC] .__generic_file_aio_write_nolock+0x350/0x3 e0 [C00000002ABBFA20] [C000000000096908] .generic_file_aio_write+0x78/0x104 [C00000002ABBFAE0] [C0000000001649F0] .ext3_file_write+0x2c/0xd4 [C00000002ABBFB70] [C0000000000C5168] .do_sync_write+0xd4/0x130 [C00000002ABBFCF0] [C0000000000C5ED4] .vfs_write+0x128/0x20c [C00000002ABBFD90] [C0000000000C664C] .sys_write+0x4c/0x8c [C00000002ABBFE30] [C00000000000871C] syscall_exit+0x0/0x40 Thanks, Badari - 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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