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[ Upstream commit62c07983be] Christophe Leroy reported a ~80ms latency spike happening at first TCP connect() time. This is because __inet_hash_connect() uses get_random_once() to populate a perturbation table which became quite big after commit4c2c8f03a5("tcp: increase source port perturb table to 2^16") get_random_once() uses DO_ONCE(), which block hard irqs for the duration of the operation. This patch adds DO_ONCE_SLOW() which uses a mutex instead of a spinlock for operations where we prefer to stay in process context. Then __inet_hash_connect() can use get_random_slow_once() to populate its perturbation table. Fixes:4c2c8f03a5("tcp: increase source port perturb table to 2^16") Fixes:190cc82489("tcp: change source port randomizarion at connect() time") Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu> Link: https://lore.kernel.org/netdev/CANn89iLAEYBaoYajy0Y9UmGFff5GPxDUoG-ErVB2jDdRNQ5Tug@mail.gmail.com/T/#t Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Willy Tarreau <w@1wt.eu> Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
99 lines
2.2 KiB
C
99 lines
2.2 KiB
C
// SPDX-License-Identifier: GPL-2.0
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/once.h>
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#include <linux/random.h>
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#include <linux/module.h>
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struct once_work {
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struct work_struct work;
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struct static_key_true *key;
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struct module *module;
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};
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static void once_deferred(struct work_struct *w)
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{
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struct once_work *work;
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work = container_of(w, struct once_work, work);
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BUG_ON(!static_key_enabled(work->key));
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static_branch_disable(work->key);
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module_put(work->module);
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kfree(work);
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}
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static void once_disable_jump(struct static_key_true *key, struct module *mod)
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{
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struct once_work *w;
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w = kmalloc(sizeof(*w), GFP_ATOMIC);
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if (!w)
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return;
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INIT_WORK(&w->work, once_deferred);
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w->key = key;
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w->module = mod;
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__module_get(mod);
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schedule_work(&w->work);
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}
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static DEFINE_SPINLOCK(once_lock);
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bool __do_once_start(bool *done, unsigned long *flags)
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__acquires(once_lock)
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{
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spin_lock_irqsave(&once_lock, *flags);
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if (*done) {
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spin_unlock_irqrestore(&once_lock, *flags);
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/* Keep sparse happy by restoring an even lock count on
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* this lock. In case we return here, we don't call into
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* __do_once_done but return early in the DO_ONCE() macro.
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*/
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__acquire(once_lock);
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return false;
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}
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return true;
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}
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EXPORT_SYMBOL(__do_once_start);
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void __do_once_done(bool *done, struct static_key_true *once_key,
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unsigned long *flags, struct module *mod)
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__releases(once_lock)
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{
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*done = true;
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spin_unlock_irqrestore(&once_lock, *flags);
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once_disable_jump(once_key, mod);
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}
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EXPORT_SYMBOL(__do_once_done);
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static DEFINE_MUTEX(once_mutex);
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bool __do_once_slow_start(bool *done)
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__acquires(once_mutex)
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{
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mutex_lock(&once_mutex);
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if (*done) {
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mutex_unlock(&once_mutex);
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/* Keep sparse happy by restoring an even lock count on
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* this mutex. In case we return here, we don't call into
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* __do_once_done but return early in the DO_ONCE_SLOW() macro.
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*/
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__acquire(once_mutex);
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return false;
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}
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return true;
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}
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EXPORT_SYMBOL(__do_once_slow_start);
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void __do_once_slow_done(bool *done, struct static_key_true *once_key,
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struct module *mod)
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__releases(once_mutex)
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{
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*done = true;
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mutex_unlock(&once_mutex);
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once_disable_jump(once_key, mod);
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}
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EXPORT_SYMBOL(__do_once_slow_done);
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