On Mon, 3 Dec 2007 11:21:37 -0500 "Ed L. Cashin" <[EMAIL PROTECTED]> wrote:
> On Sat, Dec 01, 2007 at 12:23:02PM -0800, Andrew Morton wrote: > > (switched to email - please respond via emailed reply-to-all, not via the > > bugzilla web interface) > > > > On Sat, 1 Dec 2007 11:54:11 -0800 (PST) [EMAIL PROTECTED] wrote: > > > > > http://bugzilla.kernel.org/show_bug.cgi?id=9482 > ... > > Damn that's odd. General Protection Fault in > > __set_page_dirty->__percpu_counter_add(). No sign of AOE in the trace. > > > > I assume that it is repeatable and that it doesn't occur with mkfs on > > regular local disk drives? > > I am encountering this same problem during testing of some patches I > would like to send to the LKML, applied to 2.6.24-rc3, and I can trip > this problem with just, > > echo > /dev/etherd/e7.0 > > ... at which point I get the trace below. (I had added a couple of > checks for 0xffffffffffffffff pointers to __percpu_counter_add.) I > haven't been able to check the unpatched aoe driver, but it looks the > same. > > Unable to handle kernel paging request at ffffffffffffffff RIP: > [<ffffffff8036d597>] __percpu_counter_add+0x24/0x6d > PGD 203067 PUD 204067 PMD 0 > Oops: 0000 [1] SMP > CPU 0 > Modules linked in: aoe > Pid: 2860, comm: bash Not tainted 2.6.24-rc3-47dbg #5 > RIP: 0010:[<ffffffff8036d597>] [<ffffffff8036d597>] > __percpu_counter_add+0x24/0x6d > RSP: 0018:ffff81007a0fbaa8 EFLAGS: 00010092 > RAX: ffffffffffffffff RBX: ffff81007fcc48e0 RCX: 0000000000000010 > RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff81007ace7240 > RBP: ffff81007a0fbac8 R08: ffff81007cc077b0 R09: ffffffff802ae5ee > R10: ffff81007a0fbaa8 R11: ffff810077dd99d8 R12: ffff81007ace7240 > R13: 0000000000000000 R14: 0000000000000200 R15: ffff810078473bb0 > FS: 00002ba601c5cdb0(0000) GS:ffffffff8078b000(0000) knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b > CR2: ffffffffffffffff CR3: 0000000077c31000 CR4: 00000000000006e0 > DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 > DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 > Process bash (pid: 2860, threadinfo ffff81007a0fa000, task ffff81007bf48040) > Stack: ffff81007a0fbac8 ffff81007fcc48e0 ffff81007c81c380 0000000000000000 > ffff81007a0fbaf8 ffffffff802ae682 000010007a0fbae8 ffff810078473bb0 > 0000000000000200 ffff81007fcc48e0 ffff81007a0fbb18 ffffffff802ae75c > Call Trace: > [<ffffffff802ae682>] __set_page_dirty+0xdc/0x121 > [<ffffffff802ae75c>] mark_buffer_dirty+0x95/0x99 > [<ffffffff802ae7d2>] __block_commit_write+0x72/0xac > [<ffffffff802ae988>] block_write_end+0x4f/0x5b > [<ffffffff802b243f>] blkdev_write_end+0x1b/0x38 > [<ffffffff80265d96>] generic_file_buffered_write+0x1c0/0x648 > [<ffffffff8023a752>] current_fs_time+0x22/0x29 > [<ffffffff80266576>] __generic_file_aio_write_nolock+0x358/0x3c2 > [<ffffffff80266c84>] filemap_fault+0x1c4/0x320 > [<ffffffff80264cce>] unlock_page+0x2d/0x31 > [<ffffffff802666dd>] generic_file_aio_write_nolock+0x3b/0x8d > [<ffffffff8028e40f>] do_sync_write+0xe2/0x126 > [<ffffffff802497d0>] autoremove_wake_function+0x0/0x38 > [<ffffffff8058e705>] do_page_fault+0x3f8/0x7bb > [<ffffffff8028cae8>] fd_install+0x5f/0x68 > [<ffffffff8028eb98>] vfs_write+0xae/0x137 > [<ffffffff8028f102>] sys_write+0x47/0x70 > [<ffffffff8020b7ae>] system_call+0x7e/0x83 Strange. It _looks_ like we've somehow caused smp_processor_id() to return a not-possible CPU number. This code: void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch) { s64 count; s32 *pcount; int cpu = get_cpu(); pcount = per_cpu_ptr(fbc->counters, cpu); grabs a null pointer out of fbc->counters and then does the __percpu_disguise() thing on it, thus getting an address of ~0. Which I think implies that something in AOE is scribbling on task_struct, thread_info or a machine register (%fs). Quite an achievement if so... Could you debug this a bit please? Find out which CPU number __percpu_counter_add() is using, for a start? I'd do: in __percpu_counter_add(): int foo; EXPORT_SYMBOL(foo); __percpu_counter_add() { int cpu = get_cpu(); if (foo) printk("cpu:%d\n", cpu); ... } in aoe: extern int foo; { ... foo = 1; } Alternatively, just do if (!cpu_possible(cpu)) printk(...) in __percpu_counter_add(). Then you can proceed to work through the various operations which smp_processor_id() does and find out where it went wrong: print out %fs, mainly. If the cpu number is valid then perhaps something scribbled on the cpu's per-cpu memory. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
