[bcain:bcain/glink 46/71] arch/hexagon/kernel/process.c:72:2: error: call to undeclared function 'flush_smp_call_function_queue'; ISO C99 and later do not support implicit function declarations

[kernel test robot <lkp@intel.com>]

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/bcain/linux.git bcain/glink
head:   f5a983a09d006ee1c9fe4c66beca5f1f927caa04
commit: 0d2f3aa6da801431e0498989f03e5c498c538b82 [46/71] hexagon: flush SMP call-function queue before entering idle
config: hexagon-randconfig-001-20260505 (https://download.01.org/0day-ci/archive/20260505/202605051923.IzqCBvfX-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project 5bac06718f502014fade905512f1d26d578a18f3)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260505/202605051923.IzqCBvfX-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202605051923.IzqCBvfX-lkp@intel.com/

All errors (new ones prefixed by >>):

>> arch/hexagon/kernel/process.c:72:2: error: call to undeclared function 'flush_smp_call_function_queue'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
      72 |         flush_smp_call_function_queue();
         |         ^
   1 error generated.


vim +/flush_smp_call_function_queue +72 arch/hexagon/kernel/process.c

    51	
    52	/*
    53	 * Flush pending SMP call-function work before entering __vmwait().
    54	 *
    55	 * On platforms with high IPI delivery latency (e.g. Hexagon hardware
    56	 * threads behind a hypervisor under QEMU TCG emulation), the interrupt
    57	 * from __vmintop_post() can take an extremely long time to wake the
    58	 * target thread from __vmwait().  During this time, call_single_data_t
    59	 * objects sit locked on the call_single_queue.  Since v5.7 (commit
    60	 * 5a18ceca6350), smp_call_function_single_async() returns -EBUSY when
    61	 * it finds a locked CSD instead of spinning, and callers like the
    62	 * scheduler's NOHZ kick and hrtimer migration silently drop the work.
    63	 *
    64	 * By draining the queue here — with IRQs disabled but before the RCU
    65	 * idle context (ct_cpuidle_enter) — we unlock CSDs while the CPU is
    66	 * still responsive.  This shrinks the -EBUSY window to just the
    67	 * __vmwait() duration and prevents the cascading stalls that otherwise
    68	 * hang SMP boot on v5.7+ kernels.
    69	 */
    70	void arch_cpu_idle_enter(void)
    71	{
  > 72		flush_smp_call_function_queue();
    73	}
    74	

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