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Date:   Tue, 4 Apr 2023 07:04:06 +0300
From:   Dan Carpenter <error27@gmail.com>
To:     oe-kbuild@lists.linux.dev, "Paul E. McKenney" <paulmck@kernel.org>
Cc:     lkp@intel.com, oe-kbuild-all@lists.linux.dev,
        linux-kernel@vger.kernel.org
Subject: [paulmck-rcu:dev.2023.03.30a 28/35] kernel/rcu/tree.c:2149
 rcu_do_batch() error: uninitialized symbol 'jlimit'.
Message-ID: <90f95e84-842c-4273-90a3-93afd5353fd2@kili.mountain>
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tree:   https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev.2023.03.30a
head:   e222f9a512539c3f4093a55d16624d9da614800b
commit: a63baab5f60110f3631c98b55d59066f1c68c4f7 [28/35] rcu: Employ jiffies-based backstop to callback time limit
config: openrisc-randconfig-m031-20230403 (https://download.01.org/0day-ci/archive/20230404/202304041113.A5sNFc2y-lkp@intel.com/config)
compiler: or1k-linux-gcc (GCC) 12.1.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Link: https://lore.kernel.org/r/202304041113.A5sNFc2y-lkp@intel.com/

smatch warnings:
kernel/rcu/tree.c:2149 rcu_do_batch() error: uninitialized symbol 'jlimit'.

vim +/jlimit +2149 kernel/rcu/tree.c

5bb5d09cc4f868 kernel/rcu/tree.c Paul E. McKenney        2018-07-03  2065  static void rcu_do_batch(struct rcu_data *rdp)
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2066  {
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2067  	long bl;
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2068  	long count = 0;
b5374b2df0ac1c kernel/rcu/tree.c Paul E. McKenney        2020-06-23  2069  	int div;
b4e6039e8af8c2 kernel/rcu/tree.c Joel Fernandes (Google  2020-11-18  2070) 	bool __maybe_unused empty;
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2071  	unsigned long flags;
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2072  	unsigned long jlimit;
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2073  	bool jlimit_check = false;
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2074  	long pending;
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2075  	struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl);
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2076  	struct rcu_head *rhp;
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2077  	long tlimit = 0;
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2078  
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2079  	/* If no callbacks are ready, just return. */
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2080  	if (!rcu_segcblist_ready_cbs(&rdp->cblist)) {
3c779dfef2c452 kernel/rcu/tree.c Paul E. McKenney        2018-07-05  2081  		trace_rcu_batch_start(rcu_state.name,
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2082  				      rcu_segcblist_n_cbs(&rdp->cblist), 0);
3c779dfef2c452 kernel/rcu/tree.c Paul E. McKenney        2018-07-05  2083  		trace_rcu_batch_end(rcu_state.name, 0,
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2084  				    !rcu_segcblist_empty(&rdp->cblist),
4968c300e1fa53 kernel/rcutree.c  Paul E. McKenney        2011-12-07  2085  				    need_resched(), is_idle_task(current),
5103850654fdc6 kernel/rcu/tree.c Zqiang                  2022-04-29  2086  				    rcu_is_callbacks_kthread(rdp));
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2087  		return;
29c00b4a1d9e27 kernel/rcutree.c  Paul E. McKenney        2011-06-17  2088  	}
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2089  
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2090  	/*
7b65dfa32dca1b kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2091  	 * Extract the list of ready callbacks, disabling IRQs to prevent
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2092  	 * races with call_rcu() from interrupt handlers.  Leave the
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2093  	 * callback counts, as rcu_barrier() needs to be conservative.
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2094  	 */
7b65dfa32dca1b kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2095  	rcu_nocb_lock_irqsave(rdp, flags);
8146c4e2e2c197 kernel/rcutree.c  Paul E. McKenney        2012-01-10  2096  	WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
253cbbff621407 kernel/rcu/tree.c Paul E. McKenney        2022-11-14  2097  	pending = rcu_segcblist_get_seglen(&rdp->cblist, RCU_DONE_TAIL);
b5374b2df0ac1c kernel/rcu/tree.c Paul E. McKenney        2020-06-23  2098  	div = READ_ONCE(rcu_divisor);
b5374b2df0ac1c kernel/rcu/tree.c Paul E. McKenney        2020-06-23  2099  	div = div < 0 ? 7 : div > sizeof(long) * 8 - 2 ? sizeof(long) * 8 - 2 : div;
b5374b2df0ac1c kernel/rcu/tree.c Paul E. McKenney        2020-06-23  2100  	bl = max(rdp->blimit, pending >> div);
70c461b1465c5e kernel/rcu/tree.c Paul E. McKenney        2023-03-21  2101  	if ((in_serving_softirq() || rdp->rcu_cpu_kthread_status == RCU_KTHREAD_RUNNING) &&
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2102  	    (IS_ENABLED(CONFIG_RCU_DOUBLE_CHECK_CB_TIME) || unlikely(bl > 100))) {
                                                                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
jlimit is only initialized if one of these conditions is met.

a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2103  		const long npj = NSEC_PER_SEC / HZ;
a2b354b9950bb8 kernel/rcu/tree.c Paul E. McKenney        2020-06-23  2104  		long rrn = READ_ONCE(rcu_resched_ns);
a2b354b9950bb8 kernel/rcu/tree.c Paul E. McKenney        2020-06-23  2105  
a2b354b9950bb8 kernel/rcu/tree.c Paul E. McKenney        2020-06-23  2106  		rrn = rrn < NSEC_PER_MSEC ? NSEC_PER_MSEC : rrn > NSEC_PER_SEC ? NSEC_PER_SEC : rrn;
a2b354b9950bb8 kernel/rcu/tree.c Paul E. McKenney        2020-06-23  2107  		tlimit = local_clock() + rrn;
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2108  		jlimit = jiffies + (rrn + npj + 1) / npj;
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2109  		jlimit_check = true;
a2b354b9950bb8 kernel/rcu/tree.c Paul E. McKenney        2020-06-23  2110  	}
3c779dfef2c452 kernel/rcu/tree.c Paul E. McKenney        2018-07-05  2111  	trace_rcu_batch_start(rcu_state.name,
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2112  			      rcu_segcblist_n_cbs(&rdp->cblist), bl);
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2113  	rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl);
344e219d7d2b28 kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2114  	if (rcu_rdp_is_offloaded(rdp))
7f36ef82e5cf0b kernel/rcu/tree.c Paul E. McKenney        2019-05-28  2115  		rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist);
3afe7fa535491e kernel/rcu/tree.c Joel Fernandes (Google  2020-11-14  2116) 
3afe7fa535491e kernel/rcu/tree.c Joel Fernandes (Google  2020-11-14  2117) 	trace_rcu_segcb_stats(&rdp->cblist, TPS("SegCbDequeued"));
5d6742b37727e1 kernel/rcu/tree.c Paul E. McKenney        2019-05-15  2118  	rcu_nocb_unlock_irqrestore(rdp, flags);
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2119  
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2120  	/* Invoke callbacks. */
6a949b7af82db7 kernel/rcu/tree.c Paul E. McKenney        2019-07-28  2121  	tick_dep_set_task(current, TICK_DEP_BIT_RCU);
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2122  	rhp = rcu_cblist_dequeue(&rcl);
3afe7fa535491e kernel/rcu/tree.c Joel Fernandes (Google  2020-11-14  2123) 
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2124  	for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) {
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2125) 		rcu_callback_t f;
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2126) 
6bc335828056f3 kernel/rcu/tree.c Joel Fernandes (Google  2020-11-03  2127) 		count++;
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2128  		debug_rcu_head_unqueue(rhp);
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2129) 
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2130) 		rcu_lock_acquire(&rcu_callback_map);
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2131) 		trace_rcu_invoke_callback(rcu_state.name, rhp);
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2132) 
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2133) 		f = rhp->func;
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2134) 		WRITE_ONCE(rhp->func, (rcu_callback_t)0L);
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2135) 		f(rhp);
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2136) 
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2137) 		rcu_lock_release(&rcu_callback_map);
77a40f97030b27 kernel/rcu/tree.c Joel Fernandes (Google  2019-08-30  2138) 
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2139  		/*
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2140  		 * Stop only if limit reached and CPU has something to do.
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2141  		 */
3e61e95e2d095e kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2142  		if (in_serving_softirq()) {
3e61e95e2d095e kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2143  			if (count >= bl && (need_resched() || !is_idle_task(current)))
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2144  				break;
3e61e95e2d095e kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2145  			/*
3e61e95e2d095e kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2146  			 * Make sure we don't spend too much time here and deprive other
3e61e95e2d095e kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2147  			 * softirq vectors of CPU cycles.
3e61e95e2d095e kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2148  			 */
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31 @2149  			if (rcu_do_batch_check_time(count, tlimit, jlimit_check, jlimit))
                                                                                                                                                         ^^^^^^
Uninitialized?

cfcdef5e30469f kernel/rcu/tree.c Eric Dumazet            2019-07-24  2150  				break;
a554ba288845fd kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2151  		} else {
70c461b1465c5e kernel/rcu/tree.c Paul E. McKenney        2023-03-21  2152  			// In rcuc/rcuoc context, so no worries about
70c461b1465c5e kernel/rcu/tree.c Paul E. McKenney        2023-03-21  2153  			// depriving other softirq vectors of CPU cycles.
5d6742b37727e1 kernel/rcu/tree.c Paul E. McKenney        2019-05-15  2154  			local_bh_enable();
5d6742b37727e1 kernel/rcu/tree.c Paul E. McKenney        2019-05-15  2155  			lockdep_assert_irqs_enabled();
5d6742b37727e1 kernel/rcu/tree.c Paul E. McKenney        2019-05-15  2156  			cond_resched_tasks_rcu_qs();
5d6742b37727e1 kernel/rcu/tree.c Paul E. McKenney        2019-05-15  2157  			lockdep_assert_irqs_enabled();
5d6742b37727e1 kernel/rcu/tree.c Paul E. McKenney        2019-05-15  2158  			local_bh_disable();
70c461b1465c5e kernel/rcu/tree.c Paul E. McKenney        2023-03-21  2159  			// But rcuc kthreads can delay quiescent-state
70c461b1465c5e kernel/rcu/tree.c Paul E. McKenney        2023-03-21  2160  			// reporting, so check time limits for them.
70c461b1465c5e kernel/rcu/tree.c Paul E. McKenney        2023-03-21  2161  			if (rdp->rcu_cpu_kthread_status == RCU_KTHREAD_RUNNING &&
a63baab5f60110 kernel/rcu/tree.c Paul E. McKenney        2023-03-31  2162  			    rcu_do_batch_check_time(count, tlimit, jlimit_check, jlimit)) {
70c461b1465c5e kernel/rcu/tree.c Paul E. McKenney        2023-03-21  2163  				rdp->rcu_cpu_has_work = 1;
70c461b1465c5e kernel/rcu/tree.c Paul E. McKenney        2023-03-21  2164  				break;
70c461b1465c5e kernel/rcu/tree.c Paul E. McKenney        2023-03-21  2165  			}
5d6742b37727e1 kernel/rcu/tree.c Paul E. McKenney        2019-05-15  2166  		}
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2167  	}
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2168  
7b65dfa32dca1b kernel/rcu/tree.c Frederic Weisbecker     2021-10-19  2169  	rcu_nocb_lock_irqsave(rdp, flags);
e816d56fad57ba kernel/rcu/tree.c Paul E. McKenney        2020-05-01  2170  	rdp->n_cbs_invoked += count;
3c779dfef2c452 kernel/rcu/tree.c Paul E. McKenney        2018-07-05  2171  	trace_rcu_batch_end(rcu_state.name, count, !!rcl.head, need_resched(),
5103850654fdc6 kernel/rcu/tree.c Zqiang                  2022-04-29  2172  			    is_idle_task(current), rcu_is_callbacks_kthread(rdp));
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2173  
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2174  	/* Update counts and requeue any remaining callbacks. */
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2175  	rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl);
6bc335828056f3 kernel/rcu/tree.c Joel Fernandes (Google  2020-11-03  2176) 	rcu_segcblist_add_len(&rdp->cblist, -count);
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2177  
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2178  	/* Reinstate batch limit if we have worked down the excess. */
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2179  	count = rcu_segcblist_n_cbs(&rdp->cblist);
d5a9a8c3bc8068 kernel/rcu/tree.c Paul E. McKenney        2019-04-10  2180  	if (rdp->blimit >= DEFAULT_MAX_RCU_BLIMIT && count <= qlowmark)
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2181  		rdp->blimit = blimit;
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2182  
37c72e56f6b234 kernel/rcutree.c  Paul E. McKenney        2009-10-14  2183  	/* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2184  	if (count == 0 && rdp->qlen_last_fqs_check != 0) {
37c72e56f6b234 kernel/rcutree.c  Paul E. McKenney        2009-10-14  2185  		rdp->qlen_last_fqs_check = 0;
2431774f04d105 kernel/rcu/tree.c Paul E. McKenney        2021-07-20  2186  		rdp->n_force_qs_snap = READ_ONCE(rcu_state.n_force_qs);
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2187  	} else if (count < rdp->qlen_last_fqs_check - qhimark)
15fecf89e46a96 kernel/rcu/tree.c Paul E. McKenney        2017-02-08  2188  		rdp->qlen_last_fqs_check = count;
efd88b02bb9e6b kernel/rcu/tree.c Paul E. McKenney        2017-10-19  2189  
efd88b02bb9e6b kernel/rcu/tree.c Paul E. McKenney        2017-10-19  2190  	/*
efd88b02bb9e6b kernel/rcu/tree.c Paul E. McKenney        2017-10-19  2191  	 * The following usually indicates a double call_rcu().  To track
efd88b02bb9e6b kernel/rcu/tree.c Paul E. McKenney        2017-10-19  2192  	 * this down, try building with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y.
efd88b02bb9e6b kernel/rcu/tree.c Paul E. McKenney        2017-10-19  2193  	 */
b4e6039e8af8c2 kernel/rcu/tree.c Joel Fernandes (Google  2020-11-18  2194) 	empty = rcu_segcblist_empty(&rdp->cblist);
b4e6039e8af8c2 kernel/rcu/tree.c Joel Fernandes (Google  2020-11-18  2195) 	WARN_ON_ONCE(count == 0 && !empty);
d1b222c6be1f8b kernel/rcu/tree.c Paul E. McKenney        2019-07-02  2196  	WARN_ON_ONCE(!IS_ENABLED(CONFIG_RCU_NOCB_CPU) &&
b4e6039e8af8c2 kernel/rcu/tree.c Joel Fernandes (Google  2020-11-18  2197) 		     count != 0 && empty);
b4e6039e8af8c2 kernel/rcu/tree.c Joel Fernandes (Google  2020-11-18  2198) 	WARN_ON_ONCE(count == 0 && rcu_segcblist_n_segment_cbs(&rdp->cblist) != 0);
b4e6039e8af8c2 kernel/rcu/tree.c Joel Fernandes (Google  2020-11-18  2199) 	WARN_ON_ONCE(!empty && rcu_segcblist_n_segment_cbs(&rdp->cblist) == 0);
37c72e56f6b234 kernel/rcutree.c  Paul E. McKenney        2009-10-14  2200  
5d6742b37727e1 kernel/rcu/tree.c Paul E. McKenney        2019-05-15  2201  	rcu_nocb_unlock_irqrestore(rdp, flags);
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2202  
6a949b7af82db7 kernel/rcu/tree.c Paul E. McKenney        2019-07-28  2203  	tick_dep_clear_task(current, TICK_DEP_BIT_RCU);
64db4cfff99c04 kernel/rcutree.c  Paul E. McKenney        2008-12-18  2204  }

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