From: Jay Lan <jlan@sgi.com>
To: linux-ia64@vger.kernel.org
Subject: [BUG] running strace utility can cause system to hang at sys_ptrace
Date: Thu, 13 Jul 2006 17:58:17 +0000 [thread overview]
Message-ID: <44B689B9.3090902@sgi.com> (raw)
We ran into a system hang problem at sys_ptrace.
The system may hang if a user attempts to "strace" a pthreaded
application that is making frequent calls to pthread_create &
pthread_exit.
The hang is caused by a task sleeping (yield()) while holding the
tasklist_lock.
Note that the problem appears to exist ONLY on IA64. IA64 has an
ARCH-specific implementation of sys_ptrace().
The failing path is:
sys_ptrace
read_lock(&tasklist_lock);
find_thread_for_addr(child, addr);
thread_matches(p, addr)
ptrace_check_attach(thread, 0)
wait_task_inactive(child);
yield();
Failures always show 1 task sleeping with the backtrace listed
above, plus tasks on all cpus spinning waiting to write_lock the
tasklist lock.
Sleeping
Stack traceback for pid 31069
0xe00000343b800000 31069 0 3 R 0xe00000343b8003a0 strace
0xa000000100981c60 schedule+0x2460
0xa00000010007d4d0 sys_sched_yield+0x110
0xa000000100982120 yield+0x40
0xa000000100082f10 wait_task_inactive+0x170
0xa0000001000a2570 ptrace_check_attach+0x1d0
0xa00000010002e9b0 sys_ptrace+0x1f0
0xa00000010000c900 ia64_ret_from_syscall
CPU 0
0xe00000343b5f0000 4973 0 3 C 0xe00000343b5f03a0 thdcrex
0xa00000010000caa0 ia64_leave_kernel
0xa00000010053d0a0 _raw_write_lock+0x120
0xa0000001009854d0 _write_lock_irq+0x30
0xa000000100093a00 do_exit+0xae0
0xa000000100094560 sys_exit+0x20
0xa00000010000c900 ia64_ret_from_syscall
CPU 1
0xe000003038880000 4972 0 1 R 0xe0000030388803a0 thdcrex
0xa00000010000caa0 ia64_leave_kernel
0xa00000010053d0a0 _raw_write_lock+0x120
0xa0000001009854d0 _write_lock_irq+0x30
0xa0000001000880e0 copy_process+0x1f80
0xa000000100088e30 do_fork+0x150
0xa00000010000c160 sys_clone2+0x60
0xa00000010000c900 ia64_ret_from_syscall
Regards,
- jay
next reply other threads:[~2006-07-13 17:58 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-13 17:58 Jay Lan [this message]
2006-07-13 18:24 ` [BUG] running strace utility can cause system to hang at sys_ptrace Jay Lan
2006-07-13 18:45 ` Christoph Hellwig
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