From da23379f1508dba4a02feb1ed4f53122fb4ecf64 Mon Sep 17 00:00:00 2001 From: Chris Wilson Date: Mon, 8 Apr 2019 10:17:02 +0100 Subject: [PATCH] drm/i915: Use static allocation for i915_globals_park() In order to avoid the malloc inside i915_globals_park() occurring underneath a lock connected to the shrinker (thus causing circular lockdeps warnings), move the rcu_worker to a global. <4> [39.085073] ====================================================== <4> [39.085273] WARNING: possible circular locking dependency detected <4> [39.085552] 5.1.0-rc3-CI-Trybot_4088+ #1 Tainted: G U <4> [39.085752] ------------------------------------------------------ <4> [39.085949] kswapd0/32 is trying to acquire lock: <4> [39.086121] 00000000004b5f91 (wakeref#3){+.+.}, at: intel_engine_pm_put+0x1b/0x40 [i915] <4> [39.086493] but task is already holding lock: <4> [39.086682] 00000000dd009a9a (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 <4> [39.086910] which lock already depends on the new lock. <4> [39.087139] the existing dependency chain (in reverse order) is: <4> [39.087356] -> #2 (fs_reclaim){+.+.}: <4> [39.087604] fs_reclaim_acquire.part.24+0x24/0x30 <4> [39.087785] kmem_cache_alloc_trace+0x2a/0x290 <4> [39.087998] i915_globals_park+0x22/0xa0 [i915] <4> [39.088478] idle_work_handler+0x1df/0x220 [i915] <4> [39.089016] process_one_work+0x245/0x610 <4> [39.089447] worker_thread+0x37/0x380 <4> [39.089956] kthread+0x119/0x130 <4> [39.090374] ret_from_fork+0x3a/0x50 <4> [39.090868] -> #1 (wakeref#4){+.+.}: <4> [39.091569] __mutex_lock+0x8c/0x960 <4> [39.092054] atomic_dec_and_mutex_lock+0x33/0x50 <4> [39.092521] intel_gt_pm_put+0x1b/0x40 [i915] <4> [39.093047] intel_engine_park+0xeb/0x1d0 [i915] <4> [39.093514] __intel_wakeref_put_once+0x10/0x30 [i915] <4> [39.094062] i915_request_retire+0x477/0xaf0 [i915] <4> [39.094547] ring_retire_requests+0x86/0x160 [i915] <4> [39.095110] i915_retire_requests+0x58/0xc0 [i915] <4> [39.095587] i915_gem_wait_for_idle.part.22+0xb2/0xf0 [i915] <4> [39.096142] switch_to_kernel_context_sync+0x2a/0x70 [i915] <4> [39.096633] i915_gem_init+0x59c/0x9c0 [i915] <4> [39.097174] i915_driver_load+0xd96/0x1880 [i915] <4> [39.097640] i915_pci_probe+0x29/0xa0 [i915] <4> [39.098145] pci_device_probe+0xa1/0x120 <4> [39.098607] really_probe+0xf3/0x3e0 <4> [39.099031] driver_probe_device+0x10a/0x120 <4> [39.099599] device_driver_attach+0x4b/0x50 <4> [39.100033] __driver_attach+0x97/0x130 <4> [39.100525] bus_for_each_dev+0x74/0xc0 <4> [39.100954] bus_add_driver+0x13f/0x210 <4> [39.101441] driver_register+0x56/0xe0 <4> [39.101891] do_one_initcall+0x58/0x2e0 <4> [39.102319] do_init_module+0x56/0x1ea <4> [39.102805] load_module+0x2701/0x29e0 <4> [39.103231] __se_sys_finit_module+0xd3/0xf0 <4> [39.103727] do_syscall_64+0x55/0x190 <4> [39.104153] entry_SYSCALL_64_after_hwframe+0x49/0xbe <4> [39.104736] -> #0 (wakeref#3){+.+.}: <4> [39.105437] lock_acquire+0xa6/0x1c0 <4> [39.105923] __mutex_lock+0x8c/0x960 <4> [39.106345] atomic_dec_and_mutex_lock+0x33/0x50 <4> [39.106897] intel_engine_pm_put+0x1b/0x40 [i915] <4> [39.107375] i915_request_retire+0x477/0xaf0 [i915] <4> [39.107930] ring_retire_requests+0x86/0x160 [i915] <4> [39.108412] i915_retire_requests+0x58/0xc0 [i915] <4> [39.108934] i915_gem_shrink+0xd8/0x5b0 [i915] <4> [39.109431] i915_gem_shrinker_scan+0x59/0x130 [i915] <4> [39.109884] do_shrink_slab+0x131/0x3e0 <4> [39.110380] shrink_slab+0x228/0x2c0 <4> [39.110810] shrink_node+0x177/0x460 <4> [39.111317] balance_pgdat+0x239/0x580 <4> [39.111743] kswapd+0x186/0x570 <4> [39.112221] kthread+0x119/0x130 <4> [39.112641] ret_from_fork+0x3a/0x50 Signed-off-by: Chris Wilson Reviewed-by: Tvrtko Ursulin Link: https://patchwork.freedesktop.org/patch/msgid/20190408091728.20207-3-chris@chris-wilson.co.uk --- drivers/gpu/drm/i915/i915_globals.c | 74 +++++++++++++---------------- 1 file changed, 32 insertions(+), 42 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_globals.c b/drivers/gpu/drm/i915/i915_globals.c index 2f5c72e2a9d1..81e5c2ce336b 100644 --- a/drivers/gpu/drm/i915/i915_globals.c +++ b/drivers/gpu/drm/i915/i915_globals.c @@ -17,6 +17,33 @@ static LIST_HEAD(globals); +static atomic_t active; +static atomic_t epoch; +static struct park_work { + struct rcu_work work; + int epoch; +} park; + +static void i915_globals_shrink(void) +{ + struct i915_global *global; + + /* + * kmem_cache_shrink() discards empty slabs and reorders partially + * filled slabs to prioritise allocating from the mostly full slabs, + * with the aim of reducing fragmentation. + */ + list_for_each_entry(global, &globals, link) + global->shrink(); +} + +static void __i915_globals_park(struct work_struct *work) +{ + /* Confirm nothing woke up in the last grace period */ + if (park.epoch == atomic_read(&epoch)) + i915_globals_shrink(); +} + void __init i915_global_register(struct i915_global *global) { GEM_BUG_ON(!global->shrink); @@ -57,44 +84,12 @@ int __init i915_globals_init(void) } } + INIT_RCU_WORK(&park.work, __i915_globals_park); return 0; } -static void i915_globals_shrink(void) -{ - struct i915_global *global; - - /* - * kmem_cache_shrink() discards empty slabs and reorders partially - * filled slabs to prioritise allocating from the mostly full slabs, - * with the aim of reducing fragmentation. - */ - list_for_each_entry(global, &globals, link) - global->shrink(); -} - -static atomic_t active; -static atomic_t epoch; -struct park_work { - struct rcu_work work; - int epoch; -}; - -static void __i915_globals_park(struct work_struct *work) -{ - struct park_work *wrk = container_of(work, typeof(*wrk), work.work); - - /* Confirm nothing woke up in the last grace period */ - if (wrk->epoch == atomic_read(&epoch)) - i915_globals_shrink(); - - kfree(wrk); -} - void i915_globals_park(void) { - struct park_work *wrk; - /* * Defer shrinking the global slab caches (and other work) until * after a RCU grace period has completed with no activity. This @@ -107,13 +102,8 @@ void i915_globals_park(void) if (!atomic_dec_and_test(&active)) return; - wrk = kmalloc(sizeof(*wrk), GFP_KERNEL); - if (!wrk) - return; - - wrk->epoch = atomic_inc_return(&epoch); - INIT_RCU_WORK(&wrk->work, __i915_globals_park); - queue_rcu_work(system_wq, &wrk->work); + park.epoch = atomic_inc_return(&epoch); + queue_rcu_work(system_wq, &park.work); } void i915_globals_unpark(void) @@ -125,8 +115,8 @@ void i915_globals_unpark(void) void __exit i915_globals_exit(void) { /* Flush any residual park_work */ - rcu_barrier(); - flush_scheduled_work(); + atomic_inc(&epoch); + flush_rcu_work(&park.work); __i915_globals_cleanup(); -- 2.30.2