121 lines
3.9 KiB
Diff
121 lines
3.9 KiB
Diff
From 7199b197958f10d02d7b3cf236a00c87e34a0f98 Mon Sep 17 00:00:00 2001
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From: Paul Gortmaker <paul.gortmaker@windriver.com>
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Date: Fri, 21 Jun 2013 15:07:25 -0400
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Subject: [PATCH 094/365] list_bl: Make list head locking RT safe
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As per changes in include/linux/jbd_common.h for avoiding the
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bit_spin_locks on RT ("fs: jbd/jbd2: Make state lock and journal
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head lock rt safe") we do the same thing here.
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We use the non atomic __set_bit and __clear_bit inside the scope of
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the lock to preserve the ability of the existing LIST_DEBUG code to
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use the zero'th bit in the sanity checks.
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As a bit spinlock, we had no lockdep visibility into the usage
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of the list head locking. Now, if we were to implement it as a
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standard non-raw spinlock, we would see:
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BUG: sleeping function called from invalid context at kernel/rtmutex.c:658
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in_atomic(): 1, irqs_disabled(): 0, pid: 122, name: udevd
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5 locks held by udevd/122:
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#0: (&sb->s_type->i_mutex_key#7/1){+.+.+.}, at: [<ffffffff811967e8>] lock_rename+0xe8/0xf0
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#1: (rename_lock){+.+...}, at: [<ffffffff811a277c>] d_move+0x2c/0x60
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#2: (&dentry->d_lock){+.+...}, at: [<ffffffff811a0763>] dentry_lock_for_move+0xf3/0x130
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#3: (&dentry->d_lock/2){+.+...}, at: [<ffffffff811a0734>] dentry_lock_for_move+0xc4/0x130
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#4: (&dentry->d_lock/3){+.+...}, at: [<ffffffff811a0747>] dentry_lock_for_move+0xd7/0x130
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Pid: 122, comm: udevd Not tainted 3.4.47-rt62 #7
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Call Trace:
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[<ffffffff810b9624>] __might_sleep+0x134/0x1f0
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[<ffffffff817a24d4>] rt_spin_lock+0x24/0x60
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[<ffffffff811a0c4c>] __d_shrink+0x5c/0xa0
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[<ffffffff811a1b2d>] __d_drop+0x1d/0x40
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[<ffffffff811a24be>] __d_move+0x8e/0x320
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[<ffffffff811a278e>] d_move+0x3e/0x60
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[<ffffffff81199598>] vfs_rename+0x198/0x4c0
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[<ffffffff8119b093>] sys_renameat+0x213/0x240
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[<ffffffff817a2de5>] ? _raw_spin_unlock+0x35/0x60
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[<ffffffff8107781c>] ? do_page_fault+0x1ec/0x4b0
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[<ffffffff817a32ca>] ? retint_swapgs+0xe/0x13
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[<ffffffff813eb0e6>] ? trace_hardirqs_on_thunk+0x3a/0x3f
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[<ffffffff8119b0db>] sys_rename+0x1b/0x20
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[<ffffffff817a3b96>] system_call_fastpath+0x1a/0x1f
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Since we are only taking the lock during short lived list operations,
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lets assume for now that it being raw won't be a significant latency
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concern.
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Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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include/linux/list_bl.h | 28 ++++++++++++++++++++++++++--
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1 file changed, 26 insertions(+), 2 deletions(-)
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diff --git a/include/linux/list_bl.h b/include/linux/list_bl.h
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index cb483305e1f5..d3af0990f01a 100644
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--- a/include/linux/list_bl.h
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+++ b/include/linux/list_bl.h
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@@ -2,6 +2,7 @@
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#define _LINUX_LIST_BL_H
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#include <linux/list.h>
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+#include <linux/spinlock.h>
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#include <linux/bit_spinlock.h>
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/*
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@@ -32,13 +33,22 @@
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struct hlist_bl_head {
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struct hlist_bl_node *first;
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+#ifdef CONFIG_PREEMPT_RT_BASE
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+ raw_spinlock_t lock;
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+#endif
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};
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struct hlist_bl_node {
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struct hlist_bl_node *next, **pprev;
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};
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-#define INIT_HLIST_BL_HEAD(ptr) \
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- ((ptr)->first = NULL)
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+
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+static inline void INIT_HLIST_BL_HEAD(struct hlist_bl_head *h)
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+{
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+ h->first = NULL;
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+#ifdef CONFIG_PREEMPT_RT_BASE
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+ raw_spin_lock_init(&h->lock);
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+#endif
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+}
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static inline void INIT_HLIST_BL_NODE(struct hlist_bl_node *h)
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{
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@@ -118,12 +128,26 @@ static inline void hlist_bl_del_init(struct hlist_bl_node *n)
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static inline void hlist_bl_lock(struct hlist_bl_head *b)
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{
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+#ifndef CONFIG_PREEMPT_RT_BASE
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bit_spin_lock(0, (unsigned long *)b);
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+#else
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+ raw_spin_lock(&b->lock);
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+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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+ __set_bit(0, (unsigned long *)b);
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+#endif
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+#endif
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}
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static inline void hlist_bl_unlock(struct hlist_bl_head *b)
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{
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+#ifndef CONFIG_PREEMPT_RT_BASE
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__bit_spin_unlock(0, (unsigned long *)b);
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+#else
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+#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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+ __clear_bit(0, (unsigned long *)b);
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+#endif
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+ raw_spin_unlock(&b->lock);
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+#endif
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}
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static inline bool hlist_bl_is_locked(struct hlist_bl_head *b)
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--
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2.28.0
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