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asmlinkage void do_notify_resume(struct pt_regs *regs,
               unsigned long thread_flags)
{
   /*
   * The assembly code enters us with IRQs off, but it hasn't
   * informed the tracing code of that for efficiency reasons.
   * Update the trace code with the current status.
   */
   trace_hardirqs_off();

   do {
       /* Check valid user FS if needed */
       addr_limit_user_check();

       if (thread_flags & _TIF_NEED_RESCHED) {
           /* Unmask Debug and SError for the next task */
           local_daif_restore(DAIF_PROCCTX_NOIRQ);

           schedule();
       } else {
           local_daif_restore(DAIF_PROCCTX);

if (thread_flags & _TIF_UPROBE)
uprobe_notify_resume(regs);

if (thread_flags & _TIF_SIGPENDING)
do_signal(regs);

           if (thread_flags & _TIF_NOTIFY_RESUME) {
               clear_thread_flag(TIF_NOTIFY_RESUME);
               tracehook_notify_resume(regs);
               rseq_handle_notify_resume(NULL, regs);
           }

           if (thread_flags & _TIF_FOREIGN_FPSTATE)
               fpsimd_restore_current_state();
       }

       local_daif_mask();
       thread_flags = READ_ONCE(current_thread_info()->flags);
   } while (thread_flags & _TIF_WORK_MASK);
}

/*
* Load the userland FPSIMD state of 'current' from memory, but only if the
* FPSIMD state already held in the registers is /not/ the most recent FPSIMD
* state of 'current'
*/
void fpsimd_restore_current_state(void)
{
   /*
   * For the tasks that were created before we detected the absence of
   * FP/SIMD, the TIF_FOREIGN_FPSTATE could be set via fpsimd_thread_switch(),
   * e.g, init. This could be then inherited by the children processes.
   * If we later detect that the system doesn't support FP/SIMD,
   * we must clear the flag for all the tasks to indicate that the
   * FPSTATE is clean (as we can't have one) to avoid looping for ever in
   * do_notify_resume().
   */
   if (!system_supports_fpsimd()) {
       clear_thread_flag(TIF_FOREIGN_FPSTATE);
       return;
   }

get_cpu_fpsimd_context();

   if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
       task_fpsimd_load();
       fpsimd_bind_task_to_cpu();
   }

put_cpu_fpsimd_context();
}

work_pending:
   mov   x0, sp               // 'regs'
   bl   do_notify_resume
#ifdef CONFIG_TRACE_IRQFLAGS
   bl   trace_hardirqs_on       // enabled while in userspace
#endif
   ldr   x1, [tsk, #TSK_TI_FLAGS]   // re-check for single-step
   b   finish_ret_to_user
/*文章来源地址https://www.toymoban.com/news/detail-568468.html

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