117 lines
3.8 KiB
Diff
117 lines
3.8 KiB
Diff
From ada1c576f528b64d47816a874a0bf71f0b70dff0 Mon Sep 17 00:00:00 2001
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Message-Id: <ada1c576f528b64d47816a874a0bf71f0b70dff0.1592846147.git.zanussi@kernel.org>
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In-Reply-To: <07cd0dbc80b976663c80755496a03f288decfe5a.1592846146.git.zanussi@kernel.org>
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References: <07cd0dbc80b976663c80755496a03f288decfe5a.1592846146.git.zanussi@kernel.org>
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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Wed, 20 Mar 2013 18:06:20 +0100
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Subject: [PATCH 235/330] net: Add a mutex around devnet_rename_seq
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.127-rt55.tar.xz
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On RT write_seqcount_begin() disables preemption and device_rename()
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allocates memory with GFP_KERNEL and grabs later the sysfs_mutex
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mutex. Serialize with a mutex and add use the non preemption disabling
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__write_seqcount_begin().
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To avoid writer starvation, let the reader grab the mutex and release
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it when it detects a writer in progress. This keeps the normal case
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(no reader on the fly) fast.
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[ tglx: Instead of replacing the seqcount by a mutex, add the mutex ]
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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net/core/dev.c | 34 ++++++++++++++++++++--------------
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1 file changed, 20 insertions(+), 14 deletions(-)
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diff --git a/net/core/dev.c b/net/core/dev.c
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index 528b89d2ff2e..a2a3625338d4 100644
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -196,6 +196,7 @@ static unsigned int napi_gen_id = NR_CPUS;
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static DEFINE_READ_MOSTLY_HASHTABLE(napi_hash, 8);
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static seqcount_t devnet_rename_seq;
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+static DEFINE_MUTEX(devnet_rename_mutex);
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static inline void dev_base_seq_inc(struct net *net)
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{
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@@ -921,7 +922,8 @@ int netdev_get_name(struct net *net, char *name, int ifindex)
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strcpy(name, dev->name);
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rcu_read_unlock();
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if (read_seqcount_retry(&devnet_rename_seq, seq)) {
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- cond_resched();
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+ mutex_lock(&devnet_rename_mutex);
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+ mutex_unlock(&devnet_rename_mutex);
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goto retry;
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}
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@@ -1198,20 +1200,17 @@ int dev_change_name(struct net_device *dev, const char *newname)
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likely(!(dev->priv_flags & IFF_LIVE_RENAME_OK)))
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return -EBUSY;
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- write_seqcount_begin(&devnet_rename_seq);
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+ mutex_lock(&devnet_rename_mutex);
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+ __raw_write_seqcount_begin(&devnet_rename_seq);
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- if (strncmp(newname, dev->name, IFNAMSIZ) == 0) {
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- write_seqcount_end(&devnet_rename_seq);
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- return 0;
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- }
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+ if (strncmp(newname, dev->name, IFNAMSIZ) == 0)
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+ goto outunlock;
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memcpy(oldname, dev->name, IFNAMSIZ);
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err = dev_get_valid_name(net, dev, newname);
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- if (err < 0) {
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- write_seqcount_end(&devnet_rename_seq);
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- return err;
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- }
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+ if (err < 0)
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+ goto outunlock;
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if (oldname[0] && !strchr(oldname, '%'))
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netdev_info(dev, "renamed from %s\n", oldname);
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@@ -1224,11 +1223,12 @@ int dev_change_name(struct net_device *dev, const char *newname)
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if (ret) {
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memcpy(dev->name, oldname, IFNAMSIZ);
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dev->name_assign_type = old_assign_type;
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- write_seqcount_end(&devnet_rename_seq);
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- return ret;
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+ err = ret;
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+ goto outunlock;
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}
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- write_seqcount_end(&devnet_rename_seq);
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+ __raw_write_seqcount_end(&devnet_rename_seq);
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+ mutex_unlock(&devnet_rename_mutex);
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netdev_adjacent_rename_links(dev, oldname);
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@@ -1249,7 +1249,8 @@ int dev_change_name(struct net_device *dev, const char *newname)
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/* err >= 0 after dev_alloc_name() or stores the first errno */
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if (err >= 0) {
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err = ret;
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- write_seqcount_begin(&devnet_rename_seq);
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+ mutex_lock(&devnet_rename_mutex);
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+ __raw_write_seqcount_begin(&devnet_rename_seq);
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memcpy(dev->name, oldname, IFNAMSIZ);
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memcpy(oldname, newname, IFNAMSIZ);
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dev->name_assign_type = old_assign_type;
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@@ -1262,6 +1263,11 @@ int dev_change_name(struct net_device *dev, const char *newname)
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}
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return err;
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+
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+outunlock:
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+ __raw_write_seqcount_end(&devnet_rename_seq);
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+ mutex_unlock(&devnet_rename_mutex);
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+ return err;
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}
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/**
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--
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2.17.1
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