Messages in this thread Patch in this message | | | From | Balbir Singh <> | Date | Fri, 20 Apr 2007 22:13:41 +0530 | Subject | [PATCH -mm] Taskstats fix the structure members alignment issue |
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We broke the the alignment of members of taskstats to the 8 byte boundary with the CSA patches. In the current kernel, the taskstats structure is not suitable for use by 32 bit applications in a 64 bit kernel.
On x86_64
Offsets of taskstats' members (64 bit kernel, 64 bit application)
@taskstats'offsetof[@taskstats'indices] = ( 0, # version 4, # ac_exitcode 8, # ac_flag 9, # ac_nice 16, # cpu_count 24, # cpu_delay_total 32, # blkio_count 40, # blkio_delay_total 48, # swapin_count 56, # swapin_delay_total 64, # cpu_run_real_total 72, # cpu_run_virtual_total 80, # ac_comm 112, # ac_sched 113, # ac_pad 116, # ac_uid 120, # ac_gid 124, # ac_pid 128, # ac_ppid 132, # ac_btime 136, # ac_etime 144, # ac_utime 152, # ac_stime 160, # ac_minflt 168, # ac_majflt 176, # coremem 184, # virtmem 192, # hiwater_rss 200, # hiwater_vm 208, # read_char 216, # write_char 224, # read_syscalls 232, # write_syscalls 240, # read_bytes 248, # write_bytes 256, # cancelled_write_bytes );
Offsets of taskstats' members (64 bit kernel, 32 bit application)
@taskstats'offsetof[@taskstats'indices] = ( 0, # version 4, # ac_exitcode 8, # ac_flag 9, # ac_nice 12, # cpu_count 20, # cpu_delay_total 28, # blkio_count 36, # blkio_delay_total 44, # swapin_count 52, # swapin_delay_total 60, # cpu_run_real_total 68, # cpu_run_virtual_total 76, # ac_comm 108, # ac_sched 109, # ac_pad 112, # ac_uid 116, # ac_gid 120, # ac_pid 124, # ac_ppid 128, # ac_btime 132, # ac_etime 140, # ac_utime 148, # ac_stime 156, # ac_minflt 164, # ac_majflt 172, # coremem 180, # virtmem 188, # hiwater_rss 196, # hiwater_vm 204, # read_char 212, # write_char 220, # read_syscalls 228, # write_syscalls 236, # read_bytes 244, # write_bytes 252, # cancelled_write_bytes );
This is one way to solve the problem without re-arranging structure members is to pack the structure. The patch adds an __attribute__((aligned(8))) to the taskstats structure members so that 32 bit applications using taskstats can work with a 64 bit kernel.
Using __attribute__((packed)) would break the 64 bit alignment of members.
The fix was tested on x86_64. After the fix, we got
Offsets of taskstats' members (64 bit kernel, 64 bit application)
@taskstats'offsetof[@taskstats'indices] = ( 0, # version 4, # ac_exitcode 8, # ac_flag 9, # ac_nice 16, # cpu_count 24, # cpu_delay_total 32, # blkio_count 40, # blkio_delay_total 48, # swapin_count 56, # swapin_delay_total 64, # cpu_run_real_total 72, # cpu_run_virtual_total 80, # ac_comm 112, # ac_sched 113, # ac_pad 120, # ac_uid 124, # ac_gid 128, # ac_pid 132, # ac_ppid 136, # ac_btime 144, # ac_etime 152, # ac_utime 160, # ac_stime 168, # ac_minflt 176, # ac_majflt 184, # coremem 192, # virtmem 200, # hiwater_rss 208, # hiwater_vm 216, # read_char 224, # write_char 232, # read_syscalls 240, # write_syscalls 248, # read_bytes 256, # write_bytes 264, # cancelled_write_bytes );
Offsets of taskstats' members (64 bit kernel, 32 bit application)
@taskstats'offsetof[@taskstats'indices] = ( 0, # version 4, # ac_exitcode 8, # ac_flag 9, # ac_nice 16, # cpu_count 24, # cpu_delay_total 32, # blkio_count 40, # blkio_delay_total 48, # swapin_count 56, # swapin_delay_total 64, # cpu_run_real_total 72, # cpu_run_virtual_total 80, # ac_comm 112, # ac_sched 113, # ac_pad 120, # ac_uid 124, # ac_gid 128, # ac_pid 132, # ac_ppid 136, # ac_btime 144, # ac_etime 152, # ac_utime 160, # ac_stime 168, # ac_minflt 176, # ac_majflt 184, # coremem 192, # virtmem 200, # hiwater_rss 208, # hiwater_vm 216, # read_char 224, # write_char 232, # read_syscalls 240, # write_syscalls 248, # read_bytes 256, # write_bytes 264, # cancelled_write_bytes );
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> ---
include/linux/taskstats.h | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)
diff -puN include/linux/taskstats.h~fix-taskstats-alignment include/linux/taskstats.h --- linux-2.6.20/include/linux/taskstats.h~fix-taskstats-alignment 2007-04-19 12:28:25.000000000 +0530 +++ linux-2.6.20-balbir/include/linux/taskstats.h 2007-04-19 13:21:48.000000000 +0530 @@ -66,7 +66,7 @@ struct taskstats { /* Delay waiting for cpu, while runnable * count, delay_total NOT updated atomically */ - __u64 cpu_count; + __u64 cpu_count __attribute__((aligned(8))); __u64 cpu_delay_total; /* Following four fields atomically updated using task->delays->lock */ @@ -101,14 +101,17 @@ struct taskstats { /* Basic Accounting Fields start */ char ac_comm[TS_COMM_LEN]; /* Command name */ - __u8 ac_sched; /* Scheduling discipline */ + __u8 ac_sched __attribute__((aligned(8))); + /* Scheduling discipline */ __u8 ac_pad[3]; - __u32 ac_uid; /* User ID */ + __u32 ac_uid __attribute__((aligned(8))); + /* User ID */ __u32 ac_gid; /* Group ID */ __u32 ac_pid; /* Process ID */ __u32 ac_ppid; /* Parent process ID */ __u32 ac_btime; /* Begin time [sec since 1970] */ - __u64 ac_etime; /* Elapsed time [usec] */ + __u64 ac_etime __attribute__((aligned(8))); + /* Elapsed time [usec] */ __u64 ac_utime; /* User CPU time [usec] */ __u64 ac_stime; /* SYstem CPU time [usec] */ __u64 ac_minflt; /* Minor Page Fault Count */ _ -- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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