109 lines
3.2 KiB
Diff
109 lines
3.2 KiB
Diff
From 3f9f4bd60152113147989ef17257a50d8b5e419d Mon Sep 17 00:00:00 2001
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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 239/266] 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-4.19.31-rt18.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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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -195,6 +195,7 @@ static unsigned int napi_gen_id = NR_CPU
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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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@@ -920,7 +921,8 @@ retry:
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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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@@ -1197,20 +1199,17 @@ int dev_change_name(struct net_device *d
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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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@@ -1223,11 +1222,12 @@ rollback:
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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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@@ -1248,7 +1248,8 @@ rollback:
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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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@@ -1261,6 +1262,11 @@ rollback:
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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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