Hi Fengguang, On 10/09, Fengguang Wu wrote: > > Thanks for looking into this. Attached is the task_work.s for you.
Thanks a lot! I'm afraid I am wrong, my asm skills are close to zero... but this code looks wrong to me, and this can explain the oopses. > task_work_add: > pushl %ebp # > movl %esp, %ebp #, > pushl %edi # > pushl %esi # > pushl %ebx # > subl $12, %esp #, > call mcount > movl %eax, %edi # task, task > movl %edx, -16(%ebp) # work, %sfp > movb %cl, -21(%ebp) # notify, %sfp > .p2align 4,,15 > .L3: > movl 904(%edi), %esi # task_3(D)->task_works, head > cmpl $work_exited, %esi #, head > sete %bl #, D.14145 > andl $255, %ebx #, D.14145 > xorl %ecx, %ecx # > movl %ebx, %edx # D.14145, > movl $______f.14042, %eax #, > call ftrace_likely_update # > testl %ebx, %ebx # D.14145 > jne .L4 #, > movl -16(%ebp), %edx # %sfp, > movl %esi, (%edx) # head, work_13(D)->next > movl %esi, %eax # head, __ret > #APP > # 34 "/c/wfg/tip/kernel/task_work.c" 1 > cmpxchgl %edx,904(%edi) #, *__ptr_16 > # 0 "" 2 > #NO_APP > cmpl %eax, %esi # __ret, head > jne .L3 #, OK, we added the new work successfully, we should return 0. If we return non-zero, fput() (the likely caller) assumes that it should use the workqueues to close/free this file. Then later task_work_run() will do __fput() again. > cmpb $0, -21(%ebp) #, %sfp > je .L5 #, > movl 4(%edi), %eax # task_3(D)->stack, task_3(D)->stack > #APP > # 208 "/c/wfg/tip/arch/x86/include/asm/bitops.h" 1 > bts $1, 8(%eax); jc .L2 #, MEM[(volatile long unsigned int > *)D.14203_29], This is set_notify_resume(). Probably !CONFIG_SMP (I do not see kick_process). > # 0 "" 2 > #NO_APP > .L5: > movl $0, -20(%ebp) #, %sfp > .L2: > movl -20(%ebp), %eax # %sfp, This is what we are going to return. But note that -20(%ebp) was not initialized if TIF_NOTIFY_RESUME was already set, "jc .L2" skips .L5 above. IOW, in this case we seem to return a random value from stack. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
