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McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 04/21] rcutorture: Fix stutter_wait() return value and freelist checks Date: Thu, 30 May 2019 08:16:55 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190530151650.GA422@linux.ibm.com> References: <20190530151650.GA422@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 19053015-0060-0000-0000-00000349F81D X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011185; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000286; SDB=6.01210791; UDB=6.00636161; IPR=6.00991826; MB=3.00027120; MTD=3.00000008; XFM=3.00000015; UTC=2019-05-30 15:17:16 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19053015-0061-0000-0000-0000498E0469 Message-Id: <20190530151712.1612-4-paulmck@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-05-30_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=38 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1905300108 Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org The stutter_wait() function is supposed to return true if it actually waits and false otherwise, but it instead unconditionally returns false. Which hides a bug in rcu_torture_writer() that fails to account for the fact that one of the rcu_tortures[] array elements will normally be referenced by rcu_torture_current, and thus not be on the freelist. This commit therefore corrects the stutter_wait() return value and adds a check for rcu_torture_current to rcu_torture_writer()'s check that things get freed after everything goes quiescent. In addition, this commit causes torture_stutter() to give a bit more than one second (instead of only one jiffy) warning of the end of the stutter interval. Finally, this commit disables long-delay readers and aggressive update-side forward-progress checks while forward-progress testing is in flight. Reported-by: Sebastian Andrzej Siewior Signed-off-by: Paul E. McKenney --- kernel/rcu/rcutorture.c | 16 ++++++++++++---- kernel/torture.c | 17 +++++++++++++---- 2 files changed, 25 insertions(+), 8 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 7906ba2d9dad..954ac2b98619 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -1010,10 +1010,13 @@ rcu_torture_writer(void *arg) !rcu_gp_is_normal(); } rcu_torture_writer_state = RTWS_STUTTER; - if (stutter_wait("rcu_torture_writer")) + if (stutter_wait("rcu_torture_writer") && + !READ_ONCE(rcu_fwd_cb_nodelay)) for (i = 0; i < ARRAY_SIZE(rcu_tortures); i++) - if (list_empty(&rcu_tortures[i].rtort_free)) - WARN_ON_ONCE(1); + if (list_empty(&rcu_tortures[i].rtort_free) && + rcu_access_pointer(rcu_torture_current) != + &rcu_tortures[i]) + WARN(1, "%s: rtort_pipe_count: %d\n", __func__, rcu_tortures[i].rtort_pipe_count); } while (!torture_must_stop()); /* Reset expediting back to unexpedited. */ if (expediting > 0) @@ -1709,6 +1712,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) } /* Tight loop containing cond_resched(). */ + WRITE_ONCE(rcu_fwd_cb_nodelay, true); + cur_ops->sync(); /* Later readers see above write. */ if (selfpropcb) { WRITE_ONCE(fcs.stop, 0); cur_ops->call(&fcs.rh, rcu_torture_fwd_prog_cb); @@ -1747,6 +1752,8 @@ static void rcu_torture_fwd_prog_nr(int *tested, int *tested_tries) WARN_ON(READ_ONCE(fcs.stop) != 2); destroy_rcu_head_on_stack(&fcs.rh); } + schedule_timeout_uninterruptible(HZ / 10); /* Let kthreads recover. */ + WRITE_ONCE(rcu_fwd_cb_nodelay, false); } /* Carry out call_rcu() forward-progress testing. */ @@ -1816,7 +1823,6 @@ static void rcu_torture_fwd_prog_cr(void) cur_ops->cb_barrier(); /* Wait for callbacks to be invoked. */ (void)rcu_torture_fwd_prog_cbfree(); - WRITE_ONCE(rcu_fwd_cb_nodelay, false); if (!torture_must_stop() && !READ_ONCE(rcu_fwd_emergency_stop)) { WARN_ON(n_max_gps < MIN_FWD_CBS_LAUNDERED); pr_alert("%s Duration %lu barrier: %lu pending %ld n_launders: %ld n_launders_sa: %ld n_max_gps: %ld n_max_cbs: %ld cver %ld gps %ld\n", @@ -1827,6 +1833,8 @@ static void rcu_torture_fwd_prog_cr(void) n_max_gps, n_max_cbs, cver, gps); rcu_torture_fwd_cb_hist(); } + schedule_timeout_uninterruptible(HZ); /* Let CBs drain. */ + WRITE_ONCE(rcu_fwd_cb_nodelay, false); } diff --git a/kernel/torture.c b/kernel/torture.c index 17b2be9bde12..de0e0ecf88e1 100644 --- a/kernel/torture.c +++ b/kernel/torture.c @@ -578,10 +578,12 @@ static int stutter; bool stutter_wait(const char *title) { int spt; + bool ret = false; cond_resched_tasks_rcu_qs(); spt = READ_ONCE(stutter_pause_test); for (; spt; spt = READ_ONCE(stutter_pause_test)) { + ret = true; if (spt == 1) { schedule_timeout_interruptible(1); } else if (spt == 2) { @@ -592,7 +594,7 @@ bool stutter_wait(const char *title) } torture_shutdown_absorb(title); } - return !!spt; + return ret; } EXPORT_SYMBOL_GPL(stutter_wait); @@ -602,13 +604,20 @@ EXPORT_SYMBOL_GPL(stutter_wait); */ static int torture_stutter(void *arg) { + int wtime; + VERBOSE_TOROUT_STRING("torture_stutter task started"); do { if (!torture_must_stop() && stutter > 1) { - WRITE_ONCE(stutter_pause_test, 1); - schedule_timeout_interruptible(stutter - 1); + wtime = stutter; + if (stutter > HZ + 1) { + WRITE_ONCE(stutter_pause_test, 1); + wtime = stutter - HZ - 1; + schedule_timeout_interruptible(wtime); + wtime = HZ + 1; + } WRITE_ONCE(stutter_pause_test, 2); - schedule_timeout_interruptible(1); + schedule_timeout_interruptible(wtime); } WRITE_ONCE(stutter_pause_test, 0); if (!torture_must_stop()) -- 2.17.1