archives/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-03-08 03:44:45 +01:00
Code Issues Projects Releases Packages Wiki Activity Actions

Merge branch 'ppp-replace-per-cpu-recursion-counter-with-lock-owner-field'

Browse source 
Sebastian Andrzej Siewior says:

====================
ppp: Replace per-CPU recursion counter with lock-owner field

This is another approach to avoid relying on local_bh_disable() for
locking of per-CPU in ppp.

I redid it with the per-CPU lock and local_lock_nested_bh() as discussed
in v1. The xmit_recursion counter has been removed since it served the
same purpose as the owner field. Both were updated and checked.

The xmit_recursion looks like a counter in ppp_channel_push() but at
this point, the counter should always be 0 so it always serves as a
boolean. Therefore I removed it.

I do admit that this looks easier to review.

v2 https://lore.kernel.org/all/20250710162403.402739-1-bigeasy@linutronix.de/
v1 https://lore.kernel.org/all/20250627105013.Qtv54bEk@linutronix.de/
====================

Link: https://patch.msgid.link/20250715150806.700536-1-bigeasy@linutronix.de
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
This commit is contained in:
Paolo Abeni 2025-07-17 15:36:23 +02:00
commit a96cee9b36
1 changed files with 29 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

38
drivers/net/ppp/ppp_generic.c
View file

@ -107,6 +107,11 @@ struct ppp_file {
#define PF_TO_PPP(pf) PF_TO_X(pf, struct ppp)
#define PF_TO_CHANNEL(pf) PF_TO_X(pf, struct channel)
struct ppp_xmit_recursion {
struct task_struct *owner;
local_lock_t bh_lock;
};
/*
* Data structure describing one ppp unit.
* A ppp unit corresponds to a ppp network interface device
@ -120,7 +125,7 @@ struct ppp {
int n_channels; /* how many channels are attached 54 */
spinlock_t rlock; /* lock for receive side 58 */
spinlock_t wlock; /* lock for transmit side 5c */
int __percpu *xmit_recursion; /* xmit recursion detect */
struct ppp_xmit_recursion __percpu *xmit_recursion; /* xmit recursion detect */
int mru; /* max receive unit 60 */
unsigned int flags; /* control bits 64 */
unsigned int xstate; /* transmit state bits 68 */
@ -1249,13 +1254,18 @@ static int ppp_dev_configure(struct net *src_net, struct net_device *dev,
spin_lock_init(&ppp->rlock);
spin_lock_init(&ppp->wlock);
ppp->xmit_recursion = alloc_percpu(int);
ppp->xmit_recursion = alloc_percpu(struct ppp_xmit_recursion);
if (!ppp->xmit_recursion) {
err = -ENOMEM;
goto err1;
}
for_each_possible_cpu(cpu)
(*per_cpu_ptr(ppp->xmit_recursion, cpu)) = 0;
for_each_possible_cpu(cpu) {
struct ppp_xmit_recursion *xmit_recursion;
xmit_recursion = per_cpu_ptr(ppp->xmit_recursion, cpu);
xmit_recursion->owner = NULL;
local_lock_init(&xmit_recursion->bh_lock);
}
#ifdef CONFIG_PPP_MULTILINK
ppp->minseq = -1;
@ -1660,15 +1670,20 @@ static void __ppp_xmit_process(struct ppp *ppp, struct sk_buff *skb)
static void ppp_xmit_process(struct ppp *ppp, struct sk_buff *skb)
{
struct ppp_xmit_recursion *xmit_recursion;
local_bh_disable();
if (unlikely(*this_cpu_ptr(ppp->xmit_recursion)))
xmit_recursion = this_cpu_ptr(ppp->xmit_recursion);
if (xmit_recursion->owner == current)
goto err;
local_lock_nested_bh(&ppp->xmit_recursion->bh_lock);
xmit_recursion->owner = current;
(*this_cpu_ptr(ppp->xmit_recursion))++;
__ppp_xmit_process(ppp, skb);
(*this_cpu_ptr(ppp->xmit_recursion))--;
xmit_recursion->owner = NULL;
local_unlock_nested_bh(&ppp->xmit_recursion->bh_lock);
local_bh_enable();
return;
@ -2169,11 +2184,16 @@ static void __ppp_channel_push(struct channel *pch)
static void ppp_channel_push(struct channel *pch)
{
struct ppp_xmit_recursion *xmit_recursion;
read_lock_bh(&pch->upl);
if (pch->ppp) {
(*this_cpu_ptr(pch->ppp->xmit_recursion))++;
xmit_recursion = this_cpu_ptr(pch->ppp->xmit_recursion);
local_lock_nested_bh(&pch->ppp->xmit_recursion->bh_lock);
xmit_recursion->owner = current;
__ppp_channel_push(pch);
(*this_cpu_ptr(pch->ppp->xmit_recursion))--;
xmit_recursion->owner = NULL;
local_unlock_nested_bh(&pch->ppp->xmit_recursion->bh_lock);
} else {
__ppp_channel_push(pch);
}