tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/next
head:   909bd6e3d9e73fd0ca1d6255466573d4c3fbe321
commit: 909bd6e3d9e73fd0ca1d6255466573d4c3fbe321 [27/27] rcu: Suppress RCU CPU stall warnings while dumping trace
config: i386-randconfig-x000-201735 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        git checkout 909bd6e3d9e73fd0ca1d6255466573d4c3fbe321
        # save the attached .config to linux build tree
        make ARCH=i386 

All error/warnings (new ones prefixed by >>):

   In file included from kernel/rcu/rcuperf.c:51:0:
   kernel/rcu/rcuperf.c: In function 'rcu_perf_writer':
>> kernel/rcu/rcu.h:225:8: error: 'rcu_cpu_stall_suppress' undeclared (first use in this function)
      if (!rcu_cpu_stall_suppress) \
           ^
>> kernel/rcu/rcuperf.c:482:5: note: in expansion of macro 'rcu_ftrace_dump'
        rcu_ftrace_dump(DUMP_ALL);
        ^~~~~~~~~~~~~~~
   kernel/rcu/rcu.h:225:8: note: each undeclared identifier is reported only once for each function it appears in
      if (!rcu_cpu_stall_suppress) \
           ^
>> kernel/rcu/rcuperf.c:482:5: note: in expansion of macro 'rcu_ftrace_dump'
        rcu_ftrace_dump(DUMP_ALL);
        ^~~~~~~~~~~~~~~

vim +/rcu_cpu_stall_suppress +225 kernel/rcu/rcu.h

   214	
   215	/*
   216	 * Dump the ftrace buffer, but only one time per callsite per boot.
   217	 */
   218	#define rcu_ftrace_dump(oops_dump_mode) \
   219	do { \
   220		static atomic_t ___rfd_beenhere = ATOMIC_INIT(0); \
   221		\
   222		if (!atomic_read(&___rfd_beenhere) && \
   223		    !atomic_xchg(&___rfd_beenhere, 1)) { \
   224			tracing_off(); \
 > 225			if (!rcu_cpu_stall_suppress) \
   226				rcu_cpu_stall_suppress = 3; \
   227			ftrace_dump(oops_dump_mode); \
   228			if (rcu_cpu_stall_suppress == 3) \
   229				rcu_cpu_stall_suppress = 0; \
   230		} \
   231	} while (0)
   232	

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