Messages in this thread Patch in this message | | | Date | Sat, 10 Mar 2007 03:23:03 -0500 | From | Mathieu Desnoyers <> | Subject | [PATCH] Fix atomicity of TIF update in flush_thread() for powerpc |
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Fix atomicity of TIF update in flush_thread() for powerpc
Fixes it correctly with *_ti_thread_flag.
Race :
parent process executing : sys_ptrace() (lock_kernel()) (ptrace_get_task_struct(pid)) arch_ptrace() ptrace_detach() ptrace_disable(child); clear_singlestep(child); clear_tsk_thread_flag(child, TIF_SINGLESTEP); (which clears the TIF_SINGLESTEP flag atomically from a different process) (put_task_struct(child)) (unlock_kernel())
And at the same time, in the child process : sys_execve() do_execve() search_binary_handler() load_elf_binary() flush_old_exec() flush_thread() doing a non-atomic thread flag update
Applies on 2.6.20.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
--- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -476,8 +476,13 @@ void flush_thread(void) #ifdef CONFIG_PPC64 struct thread_info *t = current_thread_info(); - if (t->flags & _TIF_ABI_PENDING) - t->flags ^= (_TIF_ABI_PENDING | _TIF_32BIT); + if (test_ti_thread_flag(t, TIF_ABI_PENDING)) { + clear_ti_thread_flag(t, TIF_ABI_PENDING); + if (test_ti_thread_flag(t, TIF_32BIT)) + clear_ti_thread_flag(t, TIF_32BIT); + else + set_ti_thread_flag(t, TIF_32BIT); + } #endif discard_lazy_cpu_state(); -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - 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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