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ppp: convert chan_sem to a mutex

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chan_sem's read-side lock is taken under another mutex, so there is no
benefit in keeping it as an rwsem. Replace the rwsem with a mutex.

Signed-off-by: Qingfang Deng <qingfang.deng@linux.dev>
Link: https://patch.msgid.link/20260727032802.4090-1-qingfang.deng@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Qingfang Deng
2026-07-27 11:28:00 +08:00
committed by Jakub Kicinski
parent 11291f1230
commit 2bb54b49e9
1 changed files with 7 additions and 7 deletions
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14
drivers/net/ppp/ppp_generic.c
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@@ -39,7 +39,6 @@
#include <linux/ip.h>
#include <linux/tcp.h>
#include <linux/spinlock.h>
#include <linux/rwsem.h>
#include <linux/stddef.h>
#include <linux/device.h>
#include <linux/mutex.h>
@@ -176,7 +175,7 @@ struct channel {
struct ppp_file file; /* stuff for read/write/poll */
struct list_head list; /* link in all/new_channels list */
struct ppp_channel *chan; /* public channel data structure */
struct rw_semaphore chan_sem; /* protects `chan' during chan ioctl */
struct mutex chan_sem; /* protects `chan' during chan ioctl */
spinlock_t downl; /* protects `chan', file.xq dequeue */
struct ppp __rcu *ppp; /* ppp unit we're connected to */
struct net *chan_net; /* the net channel belongs to */
@@ -788,12 +787,12 @@ static long ppp_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
break;
default:
down_read(&pch->chan_sem);
mutex_lock(&pch->chan_sem);
chan = pch->chan;
err = -ENOTTY;
if (chan && chan->ops->ioctl)
err = chan->ops->ioctl(chan, cmd, arg);
up_read(&pch->chan_sem);
mutex_unlock(&pch->chan_sem);
}
goto out;
}
@@ -2922,7 +2921,7 @@ int ppp_register_net_channel(struct net *net, struct ppp_channel *chan)
#ifdef CONFIG_PPP_MULTILINK
pch->lastseq = -1;
#endif /* CONFIG_PPP_MULTILINK */
init_rwsem(&pch->chan_sem);
mutex_init(&pch->chan_sem);
spin_lock_init(&pch->downl);
spin_lock_init(&pch->upl);
@@ -3005,11 +3004,11 @@ ppp_unregister_channel(struct ppp_channel *chan)
* the channel's start_xmit or ioctl routine before we proceed.
*/
ppp_disconnect_channel(pch);
down_write(&pch->chan_sem);
mutex_lock(&pch->chan_sem);
spin_lock_bh(&pch->downl);
pch->chan = NULL;
spin_unlock_bh(&pch->downl);
up_write(&pch->chan_sem);
mutex_unlock(&pch->chan_sem);
pn = ppp_pernet(pch->chan_net);
spin_lock_bh(&pn->all_channels_lock);
@@ -3600,6 +3599,7 @@ static void ppp_release_channel(struct channel *pch)
pr_err("ppp: destroying undead channel %p !\n", pch);
return;
}
mutex_destroy(&pch->chan_sem);
call_rcu(&pch->rcu, ppp_release_channel_free);
}