Hi GURUs
I am working on application based on Freescale P1020 SDK. But for
some reasons, my application hangs in setuid(0).
The Freescale P1020 SDK is using this toolchain:
gcc-4.3.74-eglibc-2.8.74-dp-2
and the kernel is also from SDK:
linux-2.6.31.
The threads in my application are like:
main() thread - SCHED_NORMAL
|
|------- thread #a, implement a timer using SIGALRM - SCHED_RR
|
|-------- thread #b – SCHED_NORMAL - this is
who hangs at setuid(0).
|
|-------- thread #c - SCHED_RR,
waitting on a netlink FD for incomming event
I added some code in kernel, I found that my thread #b returns from
sys_setuid() successfully, with its "task_struct->state" as
TASK_RUNNING. but for some reason, it doesn't return to my user-level
application code. it seems that it stays in setuid() libc function and
another system call sys_futex(), and its kernel mode stack calltrace
is like:
[cdc25c80] [c007e5ac] __rcu_process_callbacks+0x2c4/0x3a0 (unreliable)
[cdc25d40] [c0007ef8] __switch_to+0x5c/0xcc
[cdc25d50] [c0488ab8] schedule+0x2dc/0x4c4
[cdc25db0] [c00699e0] futex_wait_queue_me+0xfc/0x134
[cdc25de0] [c0069b54] futex_wait+0x13c/0x2cc
[cdc25ec0] [c006c560] do_futex+0x58/0x1e8
[cdc25ee0] [c006c784] sys_futex+0x94/0x1e4
[cdc25f40] [c0010254] ret_from_syscall+0x0/0x3c
I notice that there was some discussion about RT thread setuid() hang,
http://linux.derkeiler.com/Mailing-Lists/Kernel/2009-02/msg09870.html
but that fix is already in kernel.2.6.31, and my thread is
SCHED_NORMAL, not RT. so I guess it is not like my case.
And this is some kernel configurations:
CONFIG_TREE_RCU=y
# CONFIG_TREE_PREEMPT_RCU is not set
# CONFIG_RCU_TRACE is not set
CONFIG_RCU_FANOUT=32
# CONFIG_RCU_FANOUT_EXACT is not set
# CONFIG_TREE_RCU_TRACE is not set
CONFIG_IKCONFIG=y
CONFIG_IKCONFIG_PROC=y
CONFIG_LOG_BUF_SHIFT=14
CONFIG_GROUP_SCHED=y
# CONFIG_FAIR_GROUP_SCHED is not set
# CONFIG_RT_GROUP_SCHED is not set
CONFIG_USER_SCHED=y
# CONFIG_CGROUP_SCHED is not set
# CONFIG_CGROUPS is not set
CONFIG_PREEMPT_NONE=y
# CONFIG_PREEMPT_VOLUNTARY is not set
# CONFIG_PREEMPT is not set
CONFIG_PREEMPT is not set, but setuid() hangs no matter
whether or not it is set.
Any way, I am completely out of ideas.
Is this caused by the toolchain of Freescale P1020 SDK? Do you have
any ideas about what I should do to debug this issue?
I would appreciate it a lot if you GURUs could give me some idea. If
you need me to provide more information, please let me know.
thanks
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