条件跳转或移动取决于未初始化的值（分段错误/Fortran）

Question

我遇到了分段错误。所以，我决定使用 valgrind。对于编译，我使用了：

gfortran -fopenmp -g HECESE_openmp.f90

为了执行，我使用了：

valgrind --track-origins=yes ./a.out

我得到的一个错误是“条件跳转或移动取决于未初始化的值”，然后是“未初始化的值是由堆栈分配创建的”。你可以在下面看到它。

==13202== Conditional jump or move depends on uninitialised value(s)
==13202==    at 0x1159DC: __procedures_MOD_grad._omp_fn.4 (HECESE_openmp.f90:690)
==13202==    by 0x4C78E75: GOMP_parallel (in /usr/lib/x86_64-linux-gnu/libgomp.so.1.0.0)
==13202==    by 0x10BF25: __procedures_MOD_grad (HECESE_openmp.f90:660)
==13202==    by 0x1123FF: MAIN__ (HECESE_openmp.f90:1063)
==13202==    by 0x113E89: main (HECESE_openmp.f90:721)
==13202==  Uninitialised value was created by a stack allocation
==13202==    at 0x10B211: __procedures_MOD_grad (HECESE_openmp.f90:482)
==13202== 
==13202== Conditional jump or move depends on uninitialised value(s)
==13202==    at 0x1159E2: __procedures_MOD_grad._omp_fn.4 (HECESE_openmp.f90:690)
==13202==    by 0x4C78E75: GOMP_parallel (in /usr/lib/x86_64-linux-gnu/libgomp.so.1.0.0)
==13202==    by 0x10BF25: __procedures_MOD_grad (HECESE_openmp.f90:660)
==13202==    by 0x1123FF: MAIN__ (HECESE_openmp.f90:1063)
==13202==    by 0x113E89: main (HECESE_openmp.f90:721)
==13202==  Uninitialised value was created by a stack allocation
==13202==    at 0x10B211: __procedures_MOD_grad (HECESE_openmp.f90:482)
==13202== 
==13202== Jump to the invalid address stated on the next line
==13202==    at 0x0: ???
==13202==    by 0x4C7BD7A: ??? (in /usr/lib/x86_64-linux-gnu/libgomp.so.1.0.0)
==13202==    by 0x4C846A7: ??? (in /usr/lib/x86_64-linux-gnu/libgomp.so.1.0.0)
==13202==    by 0x4C8304C: ??? (in /usr/lib/x86_64-linux-gnu/libgomp.so.1.0.0)
==13202==    by 0x10BF25: __procedures_MOD_grad (HECESE_openmp.f90:660)
==13202==    by 0x1123FF: MAIN__ (HECESE_openmp.f90:1063)
==13202==    by 0x113E89: main (HECESE_openmp.f90:721)
==13202==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

这是我编译的代码：

       tasklist_GRAD(5)%f_ptr => u_prime_2 !5
       tasklist_GRAD(6)%f_ptr => taux_ !6
       tasklist_GRAD(7)%f_ptr => u_prime_gauche_2 !7 
       tasklist_GRAD(8)%f_ptr => u_prime_droite_2 !8
       tasklist_GRAD(9)%f_ptr => ax_droite_1 !9
       tasklist_GRAD(10)%f_ptr => ax_gauche_1 !10
       tasklist_GRAD(11)%f_ptr => ux_droite_1 !11
       tasklist_GRAD(12)%f_ptr => ux_gauche_1 !12
       tasklist_GRAD(13)%f_ptr => u_grad_x_2 !13
       tasklist_GRAD(14)%f_ptr => u_prime_gauche_3 !14 
       tasklist_GRAD(15)%f_ptr => u_prime_droite_3 !15
       tasklist_GRAD(16)%f_ptr => ax_droite_2 !16
       tasklist_GRAD(17)%f_ptr => ax_gauche_2 !17
       tasklist_GRAD(18)%f_ptr => ux_droite_2 !18
       tasklist_GRAD(19)%f_ptr => ux_gauche_2 !19
       tasklist_GRAD(20)%f_ptr => u_grad_x_3 !20

       
       !$OMP PARALLEL PRIVATE(num_thread,nthreads) &
       !$OMP SHARED(tasklist_GRAD,threads_list,threads_list_all,tasks_ready_master) &
       !$OMP SHARED(threads_list_part1,threads_list_part2,threads_list_part3)
       num_thread=OMP_GET_THREAD_NUM()
       nthreads=OMP_GET_NUM_THREADS()


       !Thread Application Master
       if (num_thread==1) then
          do ff=5,20
             if (associated(tasklist_GRAD(ff)%f_ptr) .eqv. .true.) then
                tasks_ready_master(ff) = tasklist_GRAD(ff) 
             end if
          end do

          do ff=5,20
             if (associated(tasks_ready_master(ff)%f_ptr) .eqv. .true.) then
                tasks_ready_master(ff)%state=STATE_READY
             end if
          end do
       end if


       !Thread Master 
       if (num_thread==0) then
          allocate(threads_list(nthreads-2))
          do ff=1,nthreads-2
             threads_list(ff)=ff+1
          end do


          do ff=5,20,nthreads-2
             if (tasks_ready_master(ff)%state==STATE_READY) then
                threads_list_all(ff:ff+nthreads-3)=threads_list(:)
             end if
          end do
          threads_list_part3=threads_list_all(5:20)
       end if
       !$OMP BARRIER
       !Threads workers
       do ff=5,20
          if (num_thread==threads_list_part3(ff-4)) then
             !$OMP TASK
             call tasks_ready_master(ff)%f_ptr(self,ww,pas,cpt ,nb_element,cpt1,dt,dx,p_element,u_prime,u_prime_moins,u_prime_plus,&
                  &taux,grad_x_u,grad_t_u,grad_x_f,grad_t_f,ax_plus,ax_moins,ux_plus,ux_moins,sm,flux,tab0,tab)
             !$OMP END TASK
          end if
       end do

       !$OMP END PARALLEL

第 690 行是：if (tasks_ready_master(ff)%state==STATE_READY) 然后

对于使用的列表：

    type(tcb),dimension(20)::tasklist_GRAD,tasks_ready_master
    integer,allocatable,dimension(:)::threads_list
    integer,dimension(30)::threads_list_all
    integer,dimension(3)::threads_list_part1
    integer::threads_list_part2    
    integer,dimension(16)::threads_list_part3

我忽略错误的来源。你能帮我吗？这是我第一次使用Valgrind，也是第一次在这个网站上提问。

Answer 1

不幸的是，您将代码编辑为工作版本，这掩盖了问题所在。早期代码的相关部分读取

           !Thread Master 
           if (num_thread==0) then
...
              threads_list_part3=threads_list_all(5:20)
           end if
 
           !Threads workers
           do ff=5,20
              if (num_thread==threads_list_part3(ff-4)) then

你有竞争条件。线程零执行括号中的块，但其他线程仍然是运行并继续进入 do 循环，因此 threads_list_part3 可能在主线程初始化之前被非主线程访问它。最简单的解决方法是使用屏障来确保非主线程等待主线程完成其工作。您可以明确地执行此操作

               !Thread Master 
               if (num_thread==0) then
    ...
                  threads_list_part3=threads_list_all(5:20)
               end if
!$omp barrier     
               !Threads workers
               do ff=5,20
                  if (num_thread==threads_list_part3(ff-4)) then

或隐式地通过工作共享结构，例如 !$omp single

!$omp single
               !Thread Master 
    ...
               threads_list_part3=threads_list_all(5:20)
!$omp end single     
               !Threads workers
               do ff=5,20
                  if (num_thread==threads_list_part3(ff-4)) then

我个人认为我更喜欢第二种形式。

条件跳转或移动取决于未初始化的值（分段错误/Fortran）

Conditional jump or move depends on uninitialised value(s) (Segmentation Fault / Fortran)

fortran

valgrind

openmp

gfortran

segmentation-fault