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931656b9e2
Some libraries want to ensure they are single threaded before forking,
so making the kernel's kvm huge page recovery process a vhost task of
the user process breaks those. The minijail library used by crosvm is
one such affected application.
Defer the task to after the first VM_RUN call, which occurs after the
parent process has forked all its jailed processes. This needs to happen
only once for the kvm instance, so introduce some general-purpose
infrastructure for that, too. It's similar in concept to pthread_once;
except it is actually usable, because the callback takes a parameter.
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Alyssa Ross <hi@alyssa.is>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Message-ID: <20250123153543.2769928-1-kbusch@meta.com>
[Move call_once API to include/linux. - Paolo]
Cc: stable@vger.kernel.org
Fixes: d96c77bd4e ("KVM: x86: switch hugepage recovery thread to vhost_task")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
46 lines
1.1 KiB
C
46 lines
1.1 KiB
C
#ifndef _LINUX_CALL_ONCE_H
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#define _LINUX_CALL_ONCE_H
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#include <linux/types.h>
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#include <linux/mutex.h>
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#define ONCE_NOT_STARTED 0
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#define ONCE_RUNNING 1
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#define ONCE_COMPLETED 2
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struct once {
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atomic_t state;
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struct mutex lock;
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};
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static inline void __once_init(struct once *once, const char *name,
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struct lock_class_key *key)
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{
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atomic_set(&once->state, ONCE_NOT_STARTED);
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__mutex_init(&once->lock, name, key);
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}
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#define once_init(once) \
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do { \
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static struct lock_class_key __key; \
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__once_init((once), #once, &__key); \
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} while (0)
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static inline void call_once(struct once *once, void (*cb)(struct once *))
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{
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/* Pairs with atomic_set_release() below. */
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if (atomic_read_acquire(&once->state) == ONCE_COMPLETED)
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return;
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guard(mutex)(&once->lock);
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WARN_ON(atomic_read(&once->state) == ONCE_RUNNING);
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if (atomic_read(&once->state) != ONCE_NOT_STARTED)
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return;
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atomic_set(&once->state, ONCE_RUNNING);
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cb(once);
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atomic_set_release(&once->state, ONCE_COMPLETED);
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}
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#endif /* _LINUX_CALL_ONCE_H */
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