Messages in this thread Patch in this message | | | Subject | Patch to fixe Data Acess error in dup_fd | From | Sharyathi Nagesh <> | Date | Fri, 10 Nov 2006 15:02:01 +0530 |
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On running the Stress Test on machine for more than 72 hours following error message was observed.
0:mon> e cpu 0x0: Vector: 300 (Data Access) at [c00000007ce2f7f0] pc: c000000000060d90: .dup_fd+0x240/0x39c lr: c000000000060d6c: .dup_fd+0x21c/0x39c sp: c00000007ce2fa70 msr: 800000000000b032 dar: ffffffff00000028 dsisr: 40000000 current = 0xc000000074950980 paca = 0xc000000000454500 pid = 27330, comm = bash
0:mon> t [c00000007ce2fa70] c000000000060d28 .dup_fd+0x1d8/0x39c (unreliable) [c00000007ce2fb30] c000000000060f48 .copy_files+0x5c/0x88 [c00000007ce2fbd0] c000000000061f5c .copy_process+0x574/0x1520 [c00000007ce2fcd0] c000000000062f88 .do_fork+0x80/0x1c4 [c00000007ce2fdc0] c000000000011790 .sys_clone+0x5c/0x74 [c00000007ce2fe30] c000000000008950 .ppc_clone+0x8/0xc --- Exception: c00 (System Call) at 000000000fee9c60 SP (fcb2e770) is in userspace
--------------------------- The problem is because of race window. When if(expand) block is executed in dup_fd unlocking of oldf->file_lock give a window for fdtable in oldf to be modified. So actual open_files in oldf may not match with open_files variable. This is the debug patch to fix the problem Please let me know of your opinion. It is generated on:2.6.19-rc1 --- kernel/fork.c.orig 2006-11-10 14:42:02.000000000 +0530 +++ kernel/fork.c 2006-11-10 14:42:30.000000000 +0530 @@ -687,6 +687,7 @@ static struct files_struct *dup_fd(struc * the latest pointer. */ spin_lock(&oldf->file_lock); + open_files = count_open_files(old_fdt); old_fdt = files_fdtable(oldf); } | |