Hi "Joel, I love your patch! Perhaps something to improve:
[auto build test WARNING on rcu/dev] [cannot apply to v5.4-rc1 next-20191004] [if your patch is applied to the wrong git tree, please drop us a note to help improve the system. BTW, we also suggest to use '--base' option to specify the base tree in git format-patch, please see https://stackoverflow.com/a/37406982] url: https://github.com/0day-ci/linux/commits/Joel-Fernandes-Google/Remove-GP_REPLAY-state-from-rcu_sync/20191005-024257 base: https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git dev config: x86_64-randconfig-b002-201939 (attached as .config) compiler: gcc-7 (Debian 7.4.0-13) 7.4.0 reproduce: # save the attached .config to linux build tree make ARCH=x86_64 If you fix the issue, kindly add following tag Reported-by: kbuild test robot <[email protected]> All warnings (new ones prefixed by >>): In file included from include/linux/export.h:44:0, from include/linux/linkage.h:7, from include/linux/kernel.h:8, from include/linux/list.h:9, from include/linux/wait.h:7, from include/linux/rcu_sync.h:13, from kernel//rcu/sync.c:10: kernel//rcu/sync.c: In function 'rcu_sync_dtor': kernel//rcu/sync.c:187:23: error: 'GP_REPLAY' undeclared (first use in this function) if (rsp->gp_state == GP_REPLAY) ^ include/linux/compiler.h:58:52: note: in definition of macro '__trace_if_var' #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond)) ^~~~ >> kernel//rcu/sync.c:187:2: note: in expansion of macro 'if' if (rsp->gp_state == GP_REPLAY) ^~ kernel//rcu/sync.c:187:23: note: each undeclared identifier is reported only once for each function it appears in if (rsp->gp_state == GP_REPLAY) ^ include/linux/compiler.h:58:52: note: in definition of macro '__trace_if_var' #define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond)) ^~~~ >> kernel//rcu/sync.c:187:2: note: in expansion of macro 'if' if (rsp->gp_state == GP_REPLAY) ^~ vim +/if +187 kernel//rcu/sync.c cc44ca848f5e51 Oleg Nesterov 2015-08-21 @10 #include <linux/rcu_sync.h> cc44ca848f5e51 Oleg Nesterov 2015-08-21 11 #include <linux/sched.h> cc44ca848f5e51 Oleg Nesterov 2015-08-21 12 6d1a4c2dfe7bb0 Joel Fernandes 2019-10-04 13 enum { GP_IDLE = 0, GP_ENTER, GP_PASSED, GP_EXIT }; cc44ca848f5e51 Oleg Nesterov 2015-08-21 14 cc44ca848f5e51 Oleg Nesterov 2015-08-21 15 #define rss_lock gp_wait.lock cc44ca848f5e51 Oleg Nesterov 2015-08-21 16 cc44ca848f5e51 Oleg Nesterov 2015-08-21 17 /** cc44ca848f5e51 Oleg Nesterov 2015-08-21 18 * rcu_sync_init() - Initialize an rcu_sync structure cc44ca848f5e51 Oleg Nesterov 2015-08-21 19 * @rsp: Pointer to rcu_sync structure to be initialized cc44ca848f5e51 Oleg Nesterov 2015-08-21 20 */ 95bf33b55ff446 Oleg Nesterov 2019-04-23 21 void rcu_sync_init(struct rcu_sync *rsp) cc44ca848f5e51 Oleg Nesterov 2015-08-21 22 { cc44ca848f5e51 Oleg Nesterov 2015-08-21 23 memset(rsp, 0, sizeof(*rsp)); cc44ca848f5e51 Oleg Nesterov 2015-08-21 24 init_waitqueue_head(&rsp->gp_wait); cc44ca848f5e51 Oleg Nesterov 2015-08-21 25 } cc44ca848f5e51 Oleg Nesterov 2015-08-21 26 3942a9bd7b5842 Peter Zijlstra 2016-08-11 27 /** 27fdb35fe99011 Paul E. McKenney 2017-10-19 28 * rcu_sync_enter_start - Force readers onto slow path for multiple updates 27fdb35fe99011 Paul E. McKenney 2017-10-19 29 * @rsp: Pointer to rcu_sync structure to use for synchronization 27fdb35fe99011 Paul E. McKenney 2017-10-19 30 * 3942a9bd7b5842 Peter Zijlstra 2016-08-11 31 * Must be called after rcu_sync_init() and before first use. 3942a9bd7b5842 Peter Zijlstra 2016-08-11 32 * 3942a9bd7b5842 Peter Zijlstra 2016-08-11 33 * Ensures rcu_sync_is_idle() returns false and rcu_sync_{enter,exit}() 3942a9bd7b5842 Peter Zijlstra 2016-08-11 34 * pairs turn into NO-OPs. 3942a9bd7b5842 Peter Zijlstra 2016-08-11 35 */ 3942a9bd7b5842 Peter Zijlstra 2016-08-11 36 void rcu_sync_enter_start(struct rcu_sync *rsp) 3942a9bd7b5842 Peter Zijlstra 2016-08-11 37 { 3942a9bd7b5842 Peter Zijlstra 2016-08-11 38 rsp->gp_count++; 3942a9bd7b5842 Peter Zijlstra 2016-08-11 39 rsp->gp_state = GP_PASSED; 3942a9bd7b5842 Peter Zijlstra 2016-08-11 40 } 3942a9bd7b5842 Peter Zijlstra 2016-08-11 41 cc44ca848f5e51 Oleg Nesterov 2015-08-21 42 89da3b94bb9741 Oleg Nesterov 2019-04-25 43 static void rcu_sync_func(struct rcu_head *rhp); cc44ca848f5e51 Oleg Nesterov 2015-08-21 44 89da3b94bb9741 Oleg Nesterov 2019-04-25 45 static void rcu_sync_call(struct rcu_sync *rsp) 89da3b94bb9741 Oleg Nesterov 2019-04-25 46 { 89da3b94bb9741 Oleg Nesterov 2019-04-25 47 call_rcu(&rsp->cb_head, rcu_sync_func); cc44ca848f5e51 Oleg Nesterov 2015-08-21 48 } cc44ca848f5e51 Oleg Nesterov 2015-08-21 49 cc44ca848f5e51 Oleg Nesterov 2015-08-21 50 /** cc44ca848f5e51 Oleg Nesterov 2015-08-21 51 * rcu_sync_func() - Callback function managing reader access to fastpath 27fdb35fe99011 Paul E. McKenney 2017-10-19 52 * @rhp: Pointer to rcu_head in rcu_sync structure to use for synchronization cc44ca848f5e51 Oleg Nesterov 2015-08-21 53 * 89da3b94bb9741 Oleg Nesterov 2019-04-25 54 * This function is passed to call_rcu() function by rcu_sync_enter() and cc44ca848f5e51 Oleg Nesterov 2015-08-21 55 * rcu_sync_exit(), so that it is invoked after a grace period following the 89da3b94bb9741 Oleg Nesterov 2019-04-25 56 * that invocation of enter/exit. 89da3b94bb9741 Oleg Nesterov 2019-04-25 57 * 89da3b94bb9741 Oleg Nesterov 2019-04-25 58 * If it is called by rcu_sync_enter() it signals that all the readers were 89da3b94bb9741 Oleg Nesterov 2019-04-25 59 * switched onto slow path. 89da3b94bb9741 Oleg Nesterov 2019-04-25 60 * 89da3b94bb9741 Oleg Nesterov 2019-04-25 61 * If it is called by rcu_sync_exit() it takes action based on events that cc44ca848f5e51 Oleg Nesterov 2015-08-21 62 * have taken place in the meantime, so that closely spaced rcu_sync_enter() cc44ca848f5e51 Oleg Nesterov 2015-08-21 63 * and rcu_sync_exit() pairs need not wait for a grace period. cc44ca848f5e51 Oleg Nesterov 2015-08-21 64 * cc44ca848f5e51 Oleg Nesterov 2015-08-21 65 * If another rcu_sync_enter() is invoked before the grace period cc44ca848f5e51 Oleg Nesterov 2015-08-21 66 * ended, reset state to allow the next rcu_sync_exit() to let the cc44ca848f5e51 Oleg Nesterov 2015-08-21 67 * readers back onto their fastpaths (after a grace period). If both cc44ca848f5e51 Oleg Nesterov 2015-08-21 68 * another rcu_sync_enter() and its matching rcu_sync_exit() are invoked cc44ca848f5e51 Oleg Nesterov 2015-08-21 69 * before the grace period ended, re-invoke call_rcu() on behalf of that cc44ca848f5e51 Oleg Nesterov 2015-08-21 70 * rcu_sync_exit(). Otherwise, set all state back to idle so that readers cc44ca848f5e51 Oleg Nesterov 2015-08-21 71 * can again use their fastpaths. cc44ca848f5e51 Oleg Nesterov 2015-08-21 72 */ 27fdb35fe99011 Paul E. McKenney 2017-10-19 73 static void rcu_sync_func(struct rcu_head *rhp) cc44ca848f5e51 Oleg Nesterov 2015-08-21 74 { 27fdb35fe99011 Paul E. McKenney 2017-10-19 75 struct rcu_sync *rsp = container_of(rhp, struct rcu_sync, cb_head); cc44ca848f5e51 Oleg Nesterov 2015-08-21 76 unsigned long flags; cc44ca848f5e51 Oleg Nesterov 2015-08-21 77 89da3b94bb9741 Oleg Nesterov 2019-04-25 78 WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_IDLE); 89da3b94bb9741 Oleg Nesterov 2019-04-25 79 WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_PASSED); cc44ca848f5e51 Oleg Nesterov 2015-08-21 80 cc44ca848f5e51 Oleg Nesterov 2015-08-21 81 spin_lock_irqsave(&rsp->rss_lock, flags); cc44ca848f5e51 Oleg Nesterov 2015-08-21 82 if (rsp->gp_count) { cc44ca848f5e51 Oleg Nesterov 2015-08-21 83 /* 89da3b94bb9741 Oleg Nesterov 2019-04-25 84 * We're at least a GP after the GP_IDLE->GP_ENTER transition. cc44ca848f5e51 Oleg Nesterov 2015-08-21 85 */ 89da3b94bb9741 Oleg Nesterov 2019-04-25 86 WRITE_ONCE(rsp->gp_state, GP_PASSED); 89da3b94bb9741 Oleg Nesterov 2019-04-25 87 wake_up_locked(&rsp->gp_wait); cc44ca848f5e51 Oleg Nesterov 2015-08-21 88 } else { cc44ca848f5e51 Oleg Nesterov 2015-08-21 89 /* 89da3b94bb9741 Oleg Nesterov 2019-04-25 90 * We're at least a GP after the last rcu_sync_exit(); eveybody 89da3b94bb9741 Oleg Nesterov 2019-04-25 91 * will now have observed the write side critical section. 89da3b94bb9741 Oleg Nesterov 2019-04-25 92 * Let 'em rip!. cc44ca848f5e51 Oleg Nesterov 2015-08-21 93 */ 89da3b94bb9741 Oleg Nesterov 2019-04-25 94 WRITE_ONCE(rsp->gp_state, GP_IDLE); cc44ca848f5e51 Oleg Nesterov 2015-08-21 95 } cc44ca848f5e51 Oleg Nesterov 2015-08-21 96 spin_unlock_irqrestore(&rsp->rss_lock, flags); cc44ca848f5e51 Oleg Nesterov 2015-08-21 97 } cc44ca848f5e51 Oleg Nesterov 2015-08-21 98 cc44ca848f5e51 Oleg Nesterov 2015-08-21 99 /** 89da3b94bb9741 Oleg Nesterov 2019-04-25 100 * rcu_sync_enter() - Force readers onto slowpath 89da3b94bb9741 Oleg Nesterov 2019-04-25 101 * @rsp: Pointer to rcu_sync structure to use for synchronization 89da3b94bb9741 Oleg Nesterov 2019-04-25 102 * 89da3b94bb9741 Oleg Nesterov 2019-04-25 103 * This function is used by updaters who need readers to make use of 89da3b94bb9741 Oleg Nesterov 2019-04-25 104 * a slowpath during the update. After this function returns, all 89da3b94bb9741 Oleg Nesterov 2019-04-25 105 * subsequent calls to rcu_sync_is_idle() will return false, which 89da3b94bb9741 Oleg Nesterov 2019-04-25 106 * tells readers to stay off their fastpaths. A later call to 89da3b94bb9741 Oleg Nesterov 2019-04-25 107 * rcu_sync_exit() re-enables reader slowpaths. 89da3b94bb9741 Oleg Nesterov 2019-04-25 108 * 89da3b94bb9741 Oleg Nesterov 2019-04-25 109 * When called in isolation, rcu_sync_enter() must wait for a grace 89da3b94bb9741 Oleg Nesterov 2019-04-25 110 * period, however, closely spaced calls to rcu_sync_enter() can 89da3b94bb9741 Oleg Nesterov 2019-04-25 111 * optimize away the grace-period wait via a state machine implemented 89da3b94bb9741 Oleg Nesterov 2019-04-25 112 * by rcu_sync_enter(), rcu_sync_exit(), and rcu_sync_func(). 89da3b94bb9741 Oleg Nesterov 2019-04-25 113 */ 89da3b94bb9741 Oleg Nesterov 2019-04-25 114 void rcu_sync_enter(struct rcu_sync *rsp) 89da3b94bb9741 Oleg Nesterov 2019-04-25 115 { 89da3b94bb9741 Oleg Nesterov 2019-04-25 116 int gp_state; 89da3b94bb9741 Oleg Nesterov 2019-04-25 117 89da3b94bb9741 Oleg Nesterov 2019-04-25 118 spin_lock_irq(&rsp->rss_lock); 89da3b94bb9741 Oleg Nesterov 2019-04-25 119 gp_state = rsp->gp_state; 89da3b94bb9741 Oleg Nesterov 2019-04-25 120 if (gp_state == GP_IDLE) { 89da3b94bb9741 Oleg Nesterov 2019-04-25 121 WRITE_ONCE(rsp->gp_state, GP_ENTER); 89da3b94bb9741 Oleg Nesterov 2019-04-25 122 WARN_ON_ONCE(rsp->gp_count); 89da3b94bb9741 Oleg Nesterov 2019-04-25 123 /* 89da3b94bb9741 Oleg Nesterov 2019-04-25 124 * Note that we could simply do rcu_sync_call(rsp) here and 89da3b94bb9741 Oleg Nesterov 2019-04-25 125 * avoid the "if (gp_state == GP_IDLE)" block below. 89da3b94bb9741 Oleg Nesterov 2019-04-25 126 * 89da3b94bb9741 Oleg Nesterov 2019-04-25 127 * However, synchronize_rcu() can be faster if rcu_expedited 89da3b94bb9741 Oleg Nesterov 2019-04-25 128 * or rcu_blocking_is_gp() is true. 89da3b94bb9741 Oleg Nesterov 2019-04-25 129 * 89da3b94bb9741 Oleg Nesterov 2019-04-25 130 * Another reason is that we can't wait for rcu callback if 89da3b94bb9741 Oleg Nesterov 2019-04-25 131 * we are called at early boot time but this shouldn't happen. 89da3b94bb9741 Oleg Nesterov 2019-04-25 132 */ 89da3b94bb9741 Oleg Nesterov 2019-04-25 133 } 89da3b94bb9741 Oleg Nesterov 2019-04-25 134 rsp->gp_count++; 89da3b94bb9741 Oleg Nesterov 2019-04-25 135 spin_unlock_irq(&rsp->rss_lock); 89da3b94bb9741 Oleg Nesterov 2019-04-25 136 89da3b94bb9741 Oleg Nesterov 2019-04-25 137 if (gp_state == GP_IDLE) { 89da3b94bb9741 Oleg Nesterov 2019-04-25 138 /* 89da3b94bb9741 Oleg Nesterov 2019-04-25 139 * See the comment above, this simply does the "synchronous" 89da3b94bb9741 Oleg Nesterov 2019-04-25 140 * call_rcu(rcu_sync_func) which does GP_ENTER -> GP_PASSED. 89da3b94bb9741 Oleg Nesterov 2019-04-25 141 */ 89da3b94bb9741 Oleg Nesterov 2019-04-25 142 synchronize_rcu(); 89da3b94bb9741 Oleg Nesterov 2019-04-25 143 rcu_sync_func(&rsp->cb_head); 89da3b94bb9741 Oleg Nesterov 2019-04-25 144 /* Not really needed, wait_event() would see GP_PASSED. */ 89da3b94bb9741 Oleg Nesterov 2019-04-25 145 return; 89da3b94bb9741 Oleg Nesterov 2019-04-25 146 } 89da3b94bb9741 Oleg Nesterov 2019-04-25 147 89da3b94bb9741 Oleg Nesterov 2019-04-25 148 wait_event(rsp->gp_wait, READ_ONCE(rsp->gp_state) >= GP_PASSED); 89da3b94bb9741 Oleg Nesterov 2019-04-25 149 } 89da3b94bb9741 Oleg Nesterov 2019-04-25 150 89da3b94bb9741 Oleg Nesterov 2019-04-25 151 /** 89da3b94bb9741 Oleg Nesterov 2019-04-25 152 * rcu_sync_exit() - Allow readers back onto fast path after grace period cc44ca848f5e51 Oleg Nesterov 2015-08-21 153 * @rsp: Pointer to rcu_sync structure to use for synchronization cc44ca848f5e51 Oleg Nesterov 2015-08-21 154 * cc44ca848f5e51 Oleg Nesterov 2015-08-21 155 * This function is used by updaters who have completed, and can therefore cc44ca848f5e51 Oleg Nesterov 2015-08-21 156 * now allow readers to make use of their fastpaths after a grace period cc44ca848f5e51 Oleg Nesterov 2015-08-21 157 * has elapsed. After this grace period has completed, all subsequent cc44ca848f5e51 Oleg Nesterov 2015-08-21 158 * calls to rcu_sync_is_idle() will return true, which tells readers that cc44ca848f5e51 Oleg Nesterov 2015-08-21 159 * they can once again use their fastpaths. cc44ca848f5e51 Oleg Nesterov 2015-08-21 160 */ cc44ca848f5e51 Oleg Nesterov 2015-08-21 161 void rcu_sync_exit(struct rcu_sync *rsp) cc44ca848f5e51 Oleg Nesterov 2015-08-21 162 { 6d1a4c2dfe7bb0 Joel Fernandes 2019-10-04 163 WARN_ON_ONCE(READ_ONCE(rsp->gp_state) < GP_PASSED); 89da3b94bb9741 Oleg Nesterov 2019-04-25 164 cc44ca848f5e51 Oleg Nesterov 2015-08-21 165 spin_lock_irq(&rsp->rss_lock); cc44ca848f5e51 Oleg Nesterov 2015-08-21 166 if (!--rsp->gp_count) { 89da3b94bb9741 Oleg Nesterov 2019-04-25 167 if (rsp->gp_state == GP_PASSED) { 89da3b94bb9741 Oleg Nesterov 2019-04-25 168 WRITE_ONCE(rsp->gp_state, GP_EXIT); 89da3b94bb9741 Oleg Nesterov 2019-04-25 169 rcu_sync_call(rsp); cc44ca848f5e51 Oleg Nesterov 2015-08-21 170 } cc44ca848f5e51 Oleg Nesterov 2015-08-21 171 } cc44ca848f5e51 Oleg Nesterov 2015-08-21 172 spin_unlock_irq(&rsp->rss_lock); cc44ca848f5e51 Oleg Nesterov 2015-08-21 173 } 07899a6e5f5613 Oleg Nesterov 2015-08-21 174 07899a6e5f5613 Oleg Nesterov 2015-08-21 175 /** 07899a6e5f5613 Oleg Nesterov 2015-08-21 176 * rcu_sync_dtor() - Clean up an rcu_sync structure 07899a6e5f5613 Oleg Nesterov 2015-08-21 177 * @rsp: Pointer to rcu_sync structure to be cleaned up 07899a6e5f5613 Oleg Nesterov 2015-08-21 178 */ 07899a6e5f5613 Oleg Nesterov 2015-08-21 179 void rcu_sync_dtor(struct rcu_sync *rsp) 07899a6e5f5613 Oleg Nesterov 2015-08-21 180 { 89da3b94bb9741 Oleg Nesterov 2019-04-25 181 int gp_state; 07899a6e5f5613 Oleg Nesterov 2015-08-21 182 89da3b94bb9741 Oleg Nesterov 2019-04-25 183 WARN_ON_ONCE(READ_ONCE(rsp->gp_count)); 89da3b94bb9741 Oleg Nesterov 2019-04-25 184 WARN_ON_ONCE(READ_ONCE(rsp->gp_state) == GP_PASSED); 07899a6e5f5613 Oleg Nesterov 2015-08-21 185 07899a6e5f5613 Oleg Nesterov 2015-08-21 186 spin_lock_irq(&rsp->rss_lock); 89da3b94bb9741 Oleg Nesterov 2019-04-25 @187 if (rsp->gp_state == GP_REPLAY) :::::: The code at line 187 was first introduced by commit :::::: 89da3b94bb97417ca2c5b0ce3a28643819030247 rcu/sync: Simplify the state machine :::::: TO: Oleg Nesterov <[email protected]> :::::: CC: Paul E. McKenney <[email protected]> --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
.config.gz
Description: application/gzip
