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-rw-r--r--broken-sleep-5.4.48+.patch152
1 files changed, 152 insertions, 0 deletions
diff --git a/broken-sleep-5.4.48+.patch b/broken-sleep-5.4.48+.patch
new file mode 100644
index 00000000000..e922de302b1
--- /dev/null
+++ b/broken-sleep-5.4.48+.patch
@@ -0,0 +1,152 @@
+From f7757368e0f0b3e108088ca7b5b8abda6faa7ebc Mon Sep 17 00:00:00 2001
+From: Peter Zijlstra <peterz@infradead.org>
+Date: Wed, 1 Apr 2020 17:40:33 -0400
+Subject: sched/core: Fix illegal RCU from offline CPUs
+
+[ Upstream commit bf2c59fce4074e55d622089b34be3a6bc95484fb ]
+
+In the CPU-offline process, it calls mmdrop() after idle entry and the
+subsequent call to cpuhp_report_idle_dead(). Once execution passes the
+call to rcu_report_dead(), RCU is ignoring the CPU, which results in
+lockdep complaining when mmdrop() uses RCU from either memcg or
+debugobjects below.
+
+Fix it by cleaning up the active_mm state from BP instead. Every arch
+which has CONFIG_HOTPLUG_CPU should have already called idle_task_exit()
+from AP. The only exception is parisc because it switches them to
+&init_mm unconditionally (see smp_boot_one_cpu() and smp_cpu_init()),
+but the patch will still work there because it calls mmgrab(&init_mm) in
+smp_cpu_init() and then should call mmdrop(&init_mm) in finish_cpu().
+
+ WARNING: suspicious RCU usage
+ -----------------------------
+ kernel/workqueue.c:710 RCU or wq_pool_mutex should be held!
+
+ other info that might help us debug this:
+
+ RCU used illegally from offline CPU!
+ Call Trace:
+ dump_stack+0xf4/0x164 (unreliable)
+ lockdep_rcu_suspicious+0x140/0x164
+ get_work_pool+0x110/0x150
+ __queue_work+0x1bc/0xca0
+ queue_work_on+0x114/0x120
+ css_release+0x9c/0xc0
+ percpu_ref_put_many+0x204/0x230
+ free_pcp_prepare+0x264/0x570
+ free_unref_page+0x38/0xf0
+ __mmdrop+0x21c/0x2c0
+ idle_task_exit+0x170/0x1b0
+ pnv_smp_cpu_kill_self+0x38/0x2e0
+ cpu_die+0x48/0x64
+ arch_cpu_idle_dead+0x30/0x50
+ do_idle+0x2f4/0x470
+ cpu_startup_entry+0x38/0x40
+ start_secondary+0x7a8/0xa80
+ start_secondary_resume+0x10/0x14
+
+Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
+Signed-off-by: Qian Cai <cai@lca.pw>
+Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
+Acked-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)
+Link: https://lkml.kernel.org/r/20200401214033.8448-1-cai@lca.pw
+Signed-off-by: Sasha Levin <sashal@kernel.org>
+---
+ arch/powerpc/platforms/powernv/smp.c | 1 -
+ include/linux/sched/mm.h | 2 ++
+ kernel/cpu.c | 18 +++++++++++++++++-
+ kernel/sched/core.c | 5 +++--
+ 4 files changed, 22 insertions(+), 4 deletions(-)
+
+diff --git a/arch/powerpc/platforms/powernv/smp.c b/arch/powerpc/platforms/powernv/smp.c
+index 13e251699346..b2ba3e95bda7 100644
+--- a/arch/powerpc/platforms/powernv/smp.c
++++ b/arch/powerpc/platforms/powernv/smp.c
+@@ -167,7 +167,6 @@ static void pnv_smp_cpu_kill_self(void)
+ /* Standard hot unplug procedure */
+
+ idle_task_exit();
+- current->active_mm = NULL; /* for sanity */
+ cpu = smp_processor_id();
+ DBG("CPU%d offline\n", cpu);
+ generic_set_cpu_dead(cpu);
+diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
+index c49257a3b510..a132d875d351 100644
+--- a/include/linux/sched/mm.h
++++ b/include/linux/sched/mm.h
+@@ -49,6 +49,8 @@ static inline void mmdrop(struct mm_struct *mm)
+ __mmdrop(mm);
+ }
+
++void mmdrop(struct mm_struct *mm);
++
+ /*
+ * This has to be called after a get_task_mm()/mmget_not_zero()
+ * followed by taking the mmap_sem for writing before modifying the
+diff --git a/kernel/cpu.c b/kernel/cpu.c
+index d7890c1285bf..7527825ac7da 100644
+--- a/kernel/cpu.c
++++ b/kernel/cpu.c
+@@ -3,6 +3,7 @@
+ *
+ * This code is licenced under the GPL.
+ */
++#include <linux/sched/mm.h>
+ #include <linux/proc_fs.h>
+ #include <linux/smp.h>
+ #include <linux/init.h>
+@@ -564,6 +565,21 @@ static int bringup_cpu(unsigned int cpu)
+ return bringup_wait_for_ap(cpu);
+ }
+
++static int finish_cpu(unsigned int cpu)
++{
++ struct task_struct *idle = idle_thread_get(cpu);
++ struct mm_struct *mm = idle->active_mm;
++
++ /*
++ * idle_task_exit() will have switched to &init_mm, now
++ * clean up any remaining active_mm state.
++ */
++ if (mm != &init_mm)
++ idle->active_mm = &init_mm;
++ mmdrop(mm);
++ return 0;
++}
++
+ /*
+ * Hotplug state machine related functions
+ */
+@@ -1434,7 +1450,7 @@ static struct cpuhp_step cpuhp_hp_states[] = {
+ [CPUHP_BRINGUP_CPU] = {
+ .name = "cpu:bringup",
+ .startup.single = bringup_cpu,
+- .teardown.single = NULL,
++ .teardown.single = finish_cpu,
+ .cant_stop = true,
+ },
+ /* Final state before CPU kills itself */
+diff --git a/kernel/sched/core.c b/kernel/sched/core.c
+index e99d326fa569..4874e1468279 100644
+--- a/kernel/sched/core.c
++++ b/kernel/sched/core.c
+@@ -6177,13 +6177,14 @@ void idle_task_exit(void)
+ struct mm_struct *mm = current->active_mm;
+
+ BUG_ON(cpu_online(smp_processor_id()));
++ BUG_ON(current != this_rq()->idle);
+
+ if (mm != &init_mm) {
+ switch_mm(mm, &init_mm, current);
+- current->active_mm = &init_mm;
+ finish_arch_post_lock_switch();
+ }
+- mmdrop(mm);
++
++ /* finish_cpu(), as ran on the BP, will clean up the active_mm state */
+ }
+
+ /*
+--
+cgit 1.2.3-1.el7
+