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03f4b48eda
This suppresses sparse error generated due to the recently added rcu_assign_pointer sparse check. percpu-rwsem.c:162:9: sparse: error: incompatible types in comparison expression exit.c:316:16: sparse: error: incompatible types in comparison expression Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> [ From an RCU perspective. ] Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Lai Jiangshan <jiangshanlai@gmail.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Mike Galbraith <efault@gmx.de> Cc: Morten Rasmussen <morten.rasmussen@arm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: keescook@chromium.org Cc: kernel-hardening@lists.openwall.com Cc: kernel-team@android.com Link: https://lkml.kernel.org/r/20190321003426.160260-4-joel@joelfernandes.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
65 lines
1.8 KiB
C
65 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _LINUX_RCUWAIT_H_
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#define _LINUX_RCUWAIT_H_
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#include <linux/rcupdate.h>
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/*
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* rcuwait provides a way of blocking and waking up a single
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* task in an rcu-safe manner; where it is forbidden to use
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* after exit_notify(). task_struct is not properly rcu protected,
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* unless dealing with rcu-aware lists, ie: find_task_by_*().
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*
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* Alternatively we have task_rcu_dereference(), but the return
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* semantics have different implications which would break the
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* wakeup side. The only time @task is non-nil is when a user is
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* blocked (or checking if it needs to) on a condition, and reset
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* as soon as we know that the condition has succeeded and are
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* awoken.
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*/
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struct rcuwait {
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struct task_struct __rcu *task;
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};
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#define __RCUWAIT_INITIALIZER(name) \
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{ .task = NULL, }
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static inline void rcuwait_init(struct rcuwait *w)
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{
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w->task = NULL;
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}
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extern void rcuwait_wake_up(struct rcuwait *w);
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/*
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* The caller is responsible for locking around rcuwait_wait_event(),
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* such that writes to @task are properly serialized.
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*/
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#define rcuwait_wait_event(w, condition) \
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({ \
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/* \
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* Complain if we are called after do_exit()/exit_notify(), \
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* as we cannot rely on the rcu critical region for the \
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* wakeup side. \
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*/ \
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WARN_ON(current->exit_state); \
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\
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rcu_assign_pointer((w)->task, current); \
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for (;;) { \
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/* \
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* Implicit barrier (A) pairs with (B) in \
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* rcuwait_wake_up(). \
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*/ \
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set_current_state(TASK_UNINTERRUPTIBLE); \
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if (condition) \
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break; \
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\
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schedule(); \
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} \
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\
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WRITE_ONCE((w)->task, NULL); \
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__set_current_state(TASK_RUNNING); \
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})
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#endif /* _LINUX_RCUWAIT_H_ */
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