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livepatch,sched: Add livepatch task switching to cond_resched()

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There have been reports [1][2] of live patches failing to complete
within a reasonable amount of time due to CPU-bound kthreads.

Fix it by patching tasks in cond_resched().

There are four different flavors of cond_resched(), depending on the
kernel configuration.  Hook into all of them.

A more elegant solution might be to use a preempt notifier.  However,
non-ORC unwinders can't unwind a preempted task reliably.

[1] https://lore.kernel.org/lkml/20220507174628.2086373-1-song@kernel.org/
[2] https://lkml.kernel.org/lkml/20230120-vhost-klp-switching-v1-0-7c2b65519c43@kernel.org

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Tested-by: Seth Forshee (DigitalOcean) <sforshee@kernel.org>
Link: https://lore.kernel.org/r/4ae981466b7814ec221014fc2554b2f86f3fb70b.1677257135.git.jpoimboe@kernel.org
This commit is contained in:
Josh Poimboeuf 2023-02-24 08:50:00 -08:00 • committed by Peter Zijlstra
parent 383439d3d4
commit e3ff7c609f
6 changed files with 194 additions and 28 deletions
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29
include/linux/livepatch_sched.h Normal file
View file

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/* SPDX-License-Identifier: GPL-2.0-or-later */
#ifndef _LINUX_LIVEPATCH_SCHED_H_
#define _LINUX_LIVEPATCH_SCHED_H_
#include <linux/jump_label.h>
#include <linux/static_call_types.h>
#ifdef CONFIG_LIVEPATCH
void __klp_sched_try_switch(void);
#if !defined(CONFIG_PREEMPT_DYNAMIC) || !defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL)
DECLARE_STATIC_KEY_FALSE(klp_sched_try_switch_key);
static __always_inline void klp_sched_try_switch(void)
{
if (static_branch_unlikely(&klp_sched_try_switch_key))
__klp_sched_try_switch();
}
#endif /* !CONFIG_PREEMPT_DYNAMIC || !CONFIG_HAVE_PREEMPT_DYNAMIC_CALL */
#else /* !CONFIG_LIVEPATCH */
static inline void klp_sched_try_switch(void) {}
static inline void __klp_sched_try_switch(void) {}
#endif /* CONFIG_LIVEPATCH */
#endif /* _LINUX_LIVEPATCH_SCHED_H_ */