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From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To:     "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Kevin Hilman <khilman@kernel.org>,
        Ulf Hansson <ulf.hansson@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc:     Bjorn Andersson <bjorn.andersson@linaro.org>,
        linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] PM: domain: use per-genpd lockdep class
Date:   Fri, 11 Jun 2021 13:15:40 +0300
Message-Id: <20210611101540.3379937-3-dmitry.baryshkov@linaro.org>
In-Reply-To: <20210611101540.3379937-1-dmitry.baryshkov@linaro.org>
References: <20210611101540.3379937-1-dmitry.baryshkov@linaro.org>
MIME-Version: 1.0
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In case of nested genpds it is easy to get the following warning from
lockdep, because all genpd's mutexes share same locking class. Use the
per-genpd locking class to stop lockdep from warning about possible
deadlocks. It is not possible to directly use genpd nested locking, as
it is not the genpd code calling genpd. There are interim calls to
regulator core.

[    3.030219] ============================================
[    3.030220] WARNING: possible recursive locking detected
[    3.030221] 5.13.0-rc3-00054-gf8f0a2f2b643-dirty #2480 Not tainted
[    3.030222] --------------------------------------------
[    3.030223] kworker/u16:0/7 is trying to acquire lock:
[    3.030224] ffffde0eabd29aa0 (&genpd->mlock){+.+.}-{3:3}, at: genpd_lock_mtx+0x18/0x2c
[    3.030236]
[    3.030236] but task is already holding lock:
[    3.030236] ffffde0eabcfd6d0 (&genpd->mlock){+.+.}-{3:3}, at: genpd_lock_mtx+0x18/0x2c
[    3.030240]
[    3.030240] other info that might help us debug this:
[    3.030240]  Possible unsafe locking scenario:
[    3.030240]
[    3.030241]        CPU0
[    3.030241]        ----
[    3.030242]   lock(&genpd->mlock);
[    3.030243]   lock(&genpd->mlock);
[    3.030244]
[    3.030244]  *** DEADLOCK ***
[    3.030244]
[    3.030244]  May be due to missing lock nesting notation
[    3.030244]
[    3.030245] 6 locks held by kworker/u16:0/7:
[    3.030246]  #0: ffff6cca00010938 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1f0/0x730
[    3.030252]  #1: ffff8000100c3db0 (deferred_probe_work){+.+.}-{0:0}, at: process_one_work+0x1f0/0x730
[    3.030255]  #2: ffff6cca00ce3188 (&dev->mutex){....}-{3:3}, at: __device_attach+0x3c/0x184
[    3.030260]  #3: ffffde0eabcfd6d0 (&genpd->mlock){+.+.}-{3:3}, at: genpd_lock_mtx+0x18/0x2c
[    3.030264]  #4: ffff8000100c3968 (regulator_ww_class_acquire){+.+.}-{0:0}, at: regulator_lock_dependent+0x6c/0x1b0
[    3.030270]  #5: ffff6cca00a59158 (regulator_ww_class_mutex){+.+.}-{3:3}, at: regulator_lock_recursive+0x94/0x1d0
[    3.030273]
[    3.030273] stack backtrace:
[    3.030275] CPU: 6 PID: 7 Comm: kworker/u16:0 Not tainted 5.13.0-rc3-00054-gf8f0a2f2b643-dirty #2480
[    3.030276] Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
[    3.030278] Workqueue: events_unbound deferred_probe_work_func
[    3.030280] Call trace:
[    3.030281]  dump_backtrace+0x0/0x1a0
[    3.030284]  show_stack+0x18/0x24
[    3.030286]  dump_stack+0x108/0x188
[    3.030289]  __lock_acquire+0xa20/0x1e0c
[    3.030292]  lock_acquire.part.0+0xc8/0x320
[    3.030294]  lock_acquire+0x68/0x84
[    3.030296]  __mutex_lock+0xa0/0x4f0
[    3.030299]  mutex_lock_nested+0x40/0x50
[    3.030301]  genpd_lock_mtx+0x18/0x2c
[    3.030303]  dev_pm_genpd_set_performance_state+0x94/0x1a0
[    3.030305]  reg_domain_enable+0x28/0x4c
[    3.030308]  _regulator_do_enable+0x420/0x6b0
[    3.030310]  _regulator_enable+0x178/0x1f0
[    3.030312]  regulator_enable+0x3c/0x80
[    3.030314]  gdsc_toggle_logic+0x30/0x124
[    3.030317]  gdsc_enable+0x60/0x290
[    3.030318]  _genpd_power_on+0xc0/0x134
[    3.030320]  genpd_power_on.part.0+0xa4/0x1f0
[    3.030322]  __genpd_dev_pm_attach+0xf4/0x1b0
[    3.030324]  genpd_dev_pm_attach+0x60/0x70
[    3.030326]  dev_pm_domain_attach+0x54/0x5c
[    3.030329]  platform_probe+0x50/0xe0
[    3.030330]  really_probe+0xe4/0x510
[    3.030332]  driver_probe_device+0x64/0xcc
[    3.030333]  __device_attach_driver+0xb8/0x114
[    3.030334]  bus_for_each_drv+0x78/0xd0
[    3.030337]  __device_attach+0xdc/0x184
[    3.030338]  device_initial_probe+0x14/0x20
[    3.030339]  bus_probe_device+0x9c/0xa4
[    3.030340]  deferred_probe_work_func+0x88/0xc4
[    3.030342]  process_one_work+0x298/0x730
[    3.030343]  worker_thread+0x74/0x470
[    3.030344]  kthread+0x168/0x170
[    3.030346]  ret_from_fork+0x10/0x34

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
---
 drivers/base/power/domain.c | 25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 74219d032910..bdf439b48763 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1899,20 +1899,33 @@ static int genpd_set_default_power_state(struct generic_pm_domain *genpd)
 	return 0;
 }
 
-static void genpd_lock_init(struct generic_pm_domain *genpd)
+static int genpd_lock_init(struct generic_pm_domain *genpd)
 {
 	if (genpd->flags & GENPD_FLAG_IRQ_SAFE) {
 		spin_lock_init(&genpd->slock);
 		genpd->lock_ops = &genpd_spin_ops;
 	} else {
-		mutex_init(&genpd->mlock);
+		/* Some genpds are static, some are dynamically allocated. To
+		 * make lockdep happy always allocate the key dynamically and
+		 * register it. */
+		genpd->mlock_key = kzalloc(sizeof(genpd->mlock_key), GFP_KERNEL);
+		if (!genpd->mlock_key)
+			return -ENOMEM;
+
+		lockdep_register_key(genpd->mlock_key);
+
+		__mutex_init(&genpd->mlock, genpd->name, genpd->mlock_key);
 		genpd->lock_ops = &genpd_mtx_ops;
 	}
+
+	return 0;
 }
 
 static void genpd_lock_destroy(struct generic_pm_domain *genpd) {
-	if (!(genpd->flags & GENPD_FLAG_IRQ_SAFE))
+	if (!(genpd->flags & GENPD_FLAG_IRQ_SAFE)) {
 		mutex_destroy(&genpd->mlock);
+		kfree(genpd->mlock_key);
+	}
 }
 
 /**
@@ -1935,7 +1948,10 @@ int pm_genpd_init(struct generic_pm_domain *genpd,
 	INIT_LIST_HEAD(&genpd->child_links);
 	INIT_LIST_HEAD(&genpd->dev_list);
 	RAW_INIT_NOTIFIER_HEAD(&genpd->power_notifiers);
-	genpd_lock_init(genpd);
+	ret = genpd_lock_init(genpd);
+	if (ret)
+		return ret;
+
 	genpd->gov = gov;
 	INIT_WORK(&genpd->power_off_work, genpd_power_off_work_fn);
 	atomic_set(&genpd->sd_count, 0);
@@ -2040,7 +2056,6 @@ static int genpd_remove(struct generic_pm_domain *genpd)
 		free_cpumask_var(genpd->cpus);
 	if (genpd->free_states)
 		genpd->free_states(genpd->states, genpd->state_count);
-	genpd_lock_destroy(genpd);
 
 	pr_debug("%s: removed %s\n", __func__, genpd->name);
 
-- 
2.30.2