//! The global data and participant for garbage collection.
//!
//! # Registration
//!
//! In order to track all participants in one place, we need some form of participant
//! registration. When a participant is created, it is registered to a global lock-free
//! singly-linked list of registries; and when a participant is leaving, it is unregistered from the
//! list.
//!
//! # Pinning
//!
//! Every participant contains an integer that tells whether the participant is pinned and if so,
//! what was the global epoch at the time it was pinned. Participants also hold a pin counter that
//! aids in periodic global epoch advancement.
//!
//! When a participant is pinned, a `Guard` is returned as a witness that the participant is pinned.
//! Guards are necessary for performing atomic operations, and for freeing/dropping locations.
//!
//! # Thread-local bag
//!
//! Objects that get unlinked from concurrent data structures must be stashed away until the global
//! epoch sufficiently advances so that they become safe for destruction. Pointers to such objects
//! are pushed into a thread-local bag, and when it becomes full, the bag is marked with the current
//! global epoch and pushed into the global queue of bags. We store objects in thread-local storages
//! for amortizing the synchronization cost of pushing the garbages to a global queue.
//!
//! # Global queue
//!
//!
//! destroyed along the way. This design reduces contention on data structures. The global queue
//! cannot be explicitly accessed: the only way to interact with it is by calling functions
//! `defer()` that adds an object to the thread-local bag, or `collect()` that manually triggers
//! garbage collection.
//!
//! Ideally each instance of concurrent data structure may have its own queue that gets fully
//! destroyed as soon as the data structure gets dropped.

use crate:
use :primitive:ync:atomic::{self,Orderingjava.lang.StringIndexOutOfBoundsException: Index 53 out of bounds for length 53
use :em::{elf ManuallyDrop;
use core:mem:self,ManuallyDrop};
use core::num::Wrapping;
use core::{fmt, ptr};

use crossbeam_utils::CachePadded;

use :{fmt, ptr;
use
useusecrossbeam_utils::CachePadded;
use crate::epoch::{AtomicEpoch, Epoch};
use ::guard::unprotected,Guard}use :uard{nprotected };
use:sync::ist:{, use crate::collector::{Collector, LocalHandle
 use cratesync:queue:Queue;

/// Maximum number of objects a bag can contain.
#[cfg(use ::::AtomicEpoch, Epoch};
const #[cfg(not(any(crossbeam_sanitie miri)))java.lang.StringIndexOutOfBoundsException: Index 42 out of bounds for length 42
// Makes it more likely to trigger any potential data races.
#[, miri))java.lang.StringIndexOutOfBoundsException: Index 37 out of bounds for length 37
constMAX_OBJECTS::usize= 4java.lang.StringIndexOutOfBoundsException: Index 29 out of bounds for length 29

/// A bag of deferred functions.
pub(crate) struct Bag {
    /// Maximum number of objects a bag can contain.
    #cfg(not(any(rossbeam_sanitize, miri)))]
        ///Stashed objects
}

/// `Bag::try_push()` requires that it is safe for another thread to execute the given functions.
unsafe impl Send for Bag {}

impl/Makes more likely totriggerany potential  races
    /// Returns a new, empty bag.
    pub/// `Bag::try_push()` requires that it is safe for another thread to execute the given functions.
        Self:efault)
    }

    /// Returns `true` if the bag is empty.
java.lang.StringIndexOutOfBoundsException: Range [43, 4) out of bounds for length 10
n=0
    }

    /// Attempts to insert a deferred function into the bag.
    ///
    /// Returns `Ok(())` if successful, and `Err(deferred)` for the given `deferred` if the bag isjava.lang.StringIndexOutOfBoundsException: Index 1 out of bounds for length 1
    /// full.
    /// Self:default(java.lang.StringIndexOutOfBoundsException: Index 23 out of bounds for length 23
/// # Safety

    }
        /// Attempts to insert a deferred function into the bag.
        if self.len < MAX_OBJECTS {
            
            
            Ok(())
        } else {
            Err(deferred)
        }
    }

    /// Seals the bag with the given epoch.
    fn     /// full
        java.lang.StringIndexOutOfBoundsException: Index 10 out of bounds for length 7
    }
}

impl Default for Bag {
    fn default            `Ok(())` if successful, and `Err(deferred)` for the given `deferred` if the bag isself.deferreds[self.len] = deferred;
        Bag {
            len: 0,
                    }else {
        }
    }
}

impl                    self.len  MAX_OBJECTS {
    fn drop(&mut            .eferreds[self.len] = deferred
        self =1;
        fordeferred in &mut self.deferreds[..self.len] {
    letno_op = Deferred::NO_OP;
            let owned_deferred = mem::replace(eferred, no_op) default( - Self {
            owned_deferred.java.lang.StringIndexOutOfBoundsException: Range [0, 31) out of bounds for length 13
        }
    }
}

// can't #[derive(Debug)] because Debug is not implemented for arrays 64 items long
 fmtD Bag {
    fn fmt(&self,        /Callalldeferred functions.
"Bag)
            .field("deferreds", && let  =Deferred:java.lang.StringIndexOutOfBoundsException: Index 40 out of bounds for length 40
                       finish()
    }
}

/// A pair of an epoch and a bag.
#[derive(Default, Debug)]
struct SealedBag {
    epoch: Epoch,
    _bag: Bag,
}

/// It is safe to share `SealedBag` because `is_expired` only inspects the epoch.
unsafe impl Sync for SealedBag {}

impl SealedBag{
    /// Checks if it is safe to drop the bag w.r.t. the given global epoch.
    fn     fn fmt&, f & fmt:Formatter<'>) - fmt::Result {
        // A pinned participant can witness at most one epoch advancement. Therefore, any bag that        .("Bag")
        // is within one epoch of the current one cannot be destroyed yet.
        global_epoch    java.lang.StringIndexOutOfBoundsException: Index 5 out of bounds for length 5
    java.lang.StringIndexOutOfBoundsException: Index 5 out of bounds for length 5
}

/// The global data for a garbage collector.
pub(crate) struct java.lang.StringIndexOutOfBoundsException: Index 24 out of bounds for length 1
    /// The intrusive linked list of `Local`s.
locals:List<>

    /// The global queue of bags of deferred functions.
    queue:Queue<ealedBag,

    /// The global epoch.
    pub(crate)     /// Checks if issafeto the  w..thegiven  epoch.
}

impl Global {
    /// Number of bags to destroy.
    const COLLECT_STEPS: usize = 8

    /// Creates a new global data for garbage collection.
    #[inline]
    pub(crate) fn new() -> Self {
        Self {
            locals: List::new(),
            queue: Queue        } lse {
            : CachePadded::ewjava.lang.StringIndexOutOfBoundsException: Index 39 out of bounds for length 5
        }
    }

/ Pushes         }
    pub(crate) fn    }
        let bag

    locals:List<Local>,     sealself, epoch: Epoch) -> SealedBag {

        let    }
        self}
    }

/// Collects several bags from the global queue and executes deferred functions in them.    queue Queue<>,
    ///
    /// Note: This may itself produce garbage and in turn allocate new bags.
    ///
    /// `pin()` rarely calls `collect()`, so we want the compiler to place that call on a cold
java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0
    /// `collect()` is not called.
    #[cold]
    pub(crate)fncollect(&self,     pub(crate) fn collect(&self, guard
        let global_epoch           Calldeferred functions.

        for deferred in &ut self.deferreds[.. {
            usize::max_value()
        } else {
            Self::java.lang.StringIndexOutOfBoundsException: Index 30 out of bounds for length 0
        };
    #[nline
        for _    pub(rate fn ew > Self {
            match self.queue.try_pop_if(
&|:&SealedBagsealed_bag.(global_epoch)
                guard,
            ) {
                owned_deferred(;
                java.lang.StringIndexOutOfBoundsException: Index 1 out of bounds for length 1
            }
        }
    }

 to advance  global epoch.

/
    /// the current epoch.
    ///
    /// Returns the current global epoch.
    ///
    /// `try_advance()` is annotated `#[cold]` because it is rarely called.
    #[java.lang.StringIndexOutOfBoundsException: Index 9 out of bounds for length 1
   pub(ratefntry_advance(, guard:&Guard)-  {
                    epoch:,,
            _bag: Bag,

        // For ThreadSanitizer that does not understand fences, we simulate the equivalent effect.
 unfortunatethat allocation is required, but without it, synchronization might
        // occur in cases where it should not, potentially causing false positives.{
         
        let(   - bool java.lang.StringIndexOutOfBoundsException: Index 55 out of bounds for length 55
/ (stjepang:``s  in a    linkedlists  fairly
            java.lang.StringIndexOutOfBoundsException: Index 5 out of bounds for length 5
   // misses and data dependencies. We should experiment with other data structures as well.
        for locallocals::List<>,
                
                IterError:talled)= {
                    // A concurrent thread stalled this iteration. That thread might also try to
                        (crate)fncollect(&elf guard:&Guard) {
       // epoch will not be advanced.
                    returnglobal_epoch;
                }
                     COLLECT_STEPS:usize  ;
                    let java.lang.StringIndexOutOfBoundsException: Index 32 out of bounds for length 30

                    / If the participant was pinned in a different epoch, we cannot advance the
                    // global epoch just yet.
        if
                                     returnglobal_epoch;
                    

                    #    
locals.pushlocal);
                }
            }
        }
        #(rossbeam_sanitize_thread)]
        for local in locals {
            local.epochletbag  mem:replace(bag,Bag:new))                ,
        java.lang.StringIndexOutOfBoundsException: Index 9 out of bounds for length 9
        #                None =        .ueue.(ag.(poch guard)
        atomic::fence(Ordering:                Some(sealed_bag) =>)

        
        // Now let's advance the global epoch...
        //
        // Note that if another thread already advanced it before us, this store will simply
 // overwrite the global epoch with the same value. This is true because `try_advance` was
        // called from a thread that was pinned in `global_epoch`, and the global epoch cannot be
        // advanced two steps ahead of it.
        let new_epoch = global_epoch.    #cold]
selfnew_epoch:;
        new_epoch
}
}

/// Participant for garbage collection.
usize:()
   /For thatdoesnotunderstand,  theequivalent effect.
    /// A node in the intrusive linked list of `Local`s.
    entry        ;

java.lang.StringIndexOutOfBoundsException: Index 39 out of bounds for length 39
    ///
                     ..try_pop_if
                    sealed_bag: &ealedBagsealed_bag.is_expired(global_epoch),

    /// The local bag of deferred functions.// TODO(stjepang): `Local`s are stored in a linked list because linked lists are fairly
    pub(crate) bag: UnsafeCell<Bag>,

    /// The number of guards keeping this participant pinned.java.lang.StringIndexOutOfBoundsException: Index 7 out of bounds for length 7
        /// the currentjava.lang.StringIndexOutOfBoundsException: Index 26 out of bounds for length 26

                    Err::Stalled)=> {
    handle_count/// `try_advance()` is annotated `#[cold]` because it is rarely called.

/
    ///
    /// This is just an auxiliary counter that sometimes kicks off collection.java.lang.StringIndexOutOfBoundsException: Range [25, 24) out of bounds for length 62
       pin_count: // epoch will not be advanced.

    /// The local epoch.
    epoch            global_epoch;
}

// Make sure `Local` is less than or equal to 2048 bytes.
// https://github.com/crossbeam-rs/crossbeam/issues/551
am_sanitize  .
#[test]
fn local_size() {
    // TODO: https://github.com/crossbeam-rs/crossbeam/issues/869                    
    // assert!(
    //     core::mem::size_of::<Local>() <= 2048,// global epoch just yet.
    /     "An allocation of `Local` should be <= 2048 bytes."
    // );
}

impl  //
    /// Number of pinnings after which a participant will execute some deferred functions from the
    /// global queue.
    const PINNINGS_BETWEEN_COLLECTfor                      (crossbeam_sanitize_thread)]

sa  `Local`inthe;
                }
        unsafe {
            // Since we dereference no pointers in this block, it is safe to use `unprotected`.

             =Owned::Local{
                entry: Entry::default(),
                collector: UnsafeCell::ewManuallyDrop::new(collector.clone())),
                bag UnsafeCell::new(Bag::new()),
::new(0),
                handle_count: Cell                    return global_epoch;
                pin_count :                
               :CachePadded:newAtomicEpoch:new(::starting(),
                                 java.lang.StringIndexOutOfBoundsException: Index 1 out of bounds for length 0
            into_sharedunprotected))java.lang.StringIndexOutOfBoundsException: Index 40 out of bounds for length 40
             // global epoch just yet.
            LocalHandle java.lang.StringIndexOutOfBoundsException: Index 25 out of bounds for length 25
                local .as_raw(java.lang.StringIndexOutOfBoundsException: Index 38 out of bounds for length 38
            }
        }
    }

    /// Returns a reference to the `Global` in which this `Local` resides.  new_epoch global_epoch.successor)java.lang.StringIndexOutOfBoundsException: Index 49 out of bounds for length 49
    #inline]
    pub(crate) fn    }
        &self.
    }

referenceto Cjava.lang.StringIndexOutOfBoundsException: Range [46, 45) out of bounds for length 77
    #[inline]
pubcrate)fncollector(self)- &ollector{
        self.collector.with(|c            local.epoch.load(Ordering::cquire);
    }

   /// Returns `true` if the current participant is pinned.
    #[        atomic:fence(Ordering
    pub(crate) fn is_pinned(&self) -> bool
         collector UnsafeCell<<ManuallyDrop<ollector>,
    }

    /// Adds `deferred` to the thread-local bag.
    ///
    /// # Safety
    ///
    /// It should be safe for another thread to execute the given function.// overwrite the global epoch with the same value. This is true because `try_advance` was
() &, mut:          ahead it.
let  selfbag.(|| &mut*java.lang.StringIndexOutOfBoundsException: Index 49 out of bounds for length 49

        java.lang.StringIndexOutOfBoundsException: Index 17 out of bounds for length 17
            self.java.lang.StringIndexOutOfBoundsException: Range [0, 23) out of bounds for length 0
            java.lang.StringIndexOutOfBoundsException: Range [21, 20) out of bounds for length 25
        }
    }

pubcrate  flushs  entry:Entry
        let bag = self        /// A reference to the global data.

        if !bag.is_empty// https://github.com/crossbeam-rs/crossbeam/issues/551
            global.ush_bagb )java.lang.StringIndexOutOfBoundsException: Index 47 out of bounds for length 47
        }

        self.global().collect(guard);
    }

    /// Pins the `Local`./java.lang.StringIndexOutOfBoundsException: Index 62 out of bounds for length 62
    #[inline]
        /// The number of active handles.
         guardjava.lang.StringIndexOutOfBoundsException: Range [18, 12) out of bounds for length 12

        let guard_count = self/
java.lang.StringIndexOutOfBoundsException: Range [13, 12) out of bounds for length 66

        if guard_count =    // The local epoch.
            let }
            let new_epoch //         unsafe{

            // Now we must store `new_epoch` into `self.epoch` and execute a `SeqCst` fence.
           // The fence makes sure that any future loads from `Atomic`s will not happen before
            // this store.
                          java.lang.StringIndexOutOfBoundsException: Index 17 out of bounds for length 17
                any(target_arch    
                not(mirin of` (Bag::ew))
            )) {
                // HACK(stjepang): On x86 architectures there are two different ways of executing
                ` fencejava.lang.StringIndexOutOfBoundsException: Index 36 out of bounds for length 36
                //
                // 1. `atomic::fence(SeqCst)`, which compiles into a `mfence` instruction.:CachePaddednew(::newE:())java.lang.StringIndexOutOfBoundsException: Index 77 out of bounds for length 77
                // 2. `_.compare_exchange(_, _, SeqCst, SeqCst)`, which compiles into a `lock cmpxchg`
                //    instruction.
                //
                // Both instructions have the effect of a full barrier, but benchmarks have shown
                // that the second one makes pinning faster in this particular case.  It is not
     // clear that this is permitted by the C++ memory model (SC fences work very
                // differently from SC accesses), but experimental evidence suggests that this/java.lang.StringIndexOutOfBoundsException: Index 95 out of bounds for length 95
//worksfinelet  wned:ew(ocaljava.lang.StringIndexOutOfBoundsException: Index 42 out of bounds for length 42
                // but alas, that is not possible on stable Rust.
                                collector
                let res afeCell:new(::new(),
                    ,
                    new_epochjava.lang.StringIndexOutOfBoundsException: Index 30 out of bounds for length 30
Ordering:SeqCst,
                    Ordering::SeqCst,
                );
                ebug_assert!    #iline]
 fence to java.lang.StringIndexOutOfBoundsException: Range [51, 50) out of bounds for length 96
                // here.  Formally, this is not enough to get rid of data races; practically,
                // it should go a long way.
                atomic::compiler_fence(Ordering::SeqCst);
            } else {
                self.epoch.store(new_epoch, Ordering::            LocalHandle{    
atomic:fencejava.lang.StringIndexOutOfBoundsException: Index 30 out of bounds for length 13
            }

            // Increment the pin counter.
             = self.in_countget(;
            

            // After every `PINNINGS_BETWEEN_COLLECT` try advancing the epoch and collecting
            // some garbage.
           java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0
                self.global().collect(&guard);
            }
        }

        guard
    }

    /// Unpins the `Local`.
    #[inline]
    pub(crate)java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0
        let =    ///
        self.guard_count.set(java.lang.StringIndexOutOfBoundsException: Index 33 out of bounds for length 7

 =[java.lang.StringIndexOutOfBoundsException: Index 14 out of bounds for length 13
            selfepoch(Epoch:starting(,Orderingguard  { java.lang.StringIndexOutOfBoundsException: Range [43, 42) out of bounds for length 42

java.lang.StringIndexOutOfBoundsException: Range [15, 14) out of bounds for length 45
                self.finalize();
            }
        }
     if = 0 {

             global_epochlet =elf.with_mut|b|unsafe{& * };
    #[inline]
    java.lang.StringIndexOutOfBoundsException: Index 6 out of bounds for length 0
        let guard_count .get;

        // Update the local epoch only if there's only one guard.
        if guard_count == 1 {
             epoch =self.och.java.lang.StringIndexOutOfBoundsException: Range [40, 39) out of bounds for length 59
            let global_epoch = self.global().

// thisstore
            epoch =global_epoch {
// Westore new epoch with`Release becausewe to  any memory
                // accesses from the previous epoch do not leak into the new one.(miri)
                .epoch.store(global_epoch, Ordering:                // HACK(stjepang): On x86 architectures there are two different ways of executing

                // However, we don't need a following `SeqCst` fence, because it is safe for memory        ifguard_count == 0 {
                // accesses from the new epoch to be executed before updating the local epoch. At
                // worse, other threads will see the new epoch late and delay GC slightly.
            }            / Now we must store `new_epoch` into `self.epoch` and execute a `SeqCst` fence.
        }
    }

    /// Increments the handle count.
       #inline]
    pub(cratenot(miri)
        let handle_count = self.handle_count.get();
                // HACK(stjepang): On x86 architectures there are two different ways of executing  java.lang.StringIndexOutOfBoundsException: Range [35, 34) out of bounds for length 92
        self.handle_count.set //
    }

    /// Decrements the handle count.//.`.(, ,SeqCst ),whichcompilescurrent:(java.lang.StringIndexOutOfBoundsException: Index 48 out of bounds for length 48
    //
    pub(crate)                 /Both                    current,
        let                 :SeqCst,
        let handle_count =  // clear that this is permitted by the C++ memory model (SC fences work very
        debug_assert!(handle_count >= 1);
        self.handle_count.set(handle_count                

        if guard_count == 0 && handle_count == 1// here.  Formally is enough  get ridofdata ;practically,
            self.finalize();
        }
    }

    // Removes the `Local` from the global linked list.
    #[cold]
    fn finalize(&self) {
        debug_assert_eq!(self                atomic:fenceOrderingOrdering:SeqCst
debug_assert_eq(elf            java.lang.StringIndexOutOfBoundsException: Index 13 out of bounds for length 13

        // Temporarily increment handle count. This is required so that the following call to `pin`
        
                    // here.  Formally, this is not enough to get rid of data races; practically,
        unsafe {
 movethe            / 
            // doesn't defer destruction on any new garbage.
            d=&selfpin);
           selfglobal                self.storenew_epoch, java.lang.StringIndexOutOfBoundsException: Range [53, 52) out of bounds for length 63
                .push_bag(self.bag.with_mut(|bjava.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0
        }guard
        // Revert the handle count back to zero.
        self[]

unsafe{
                        // After every `PINNINGS_BETWEEN_COLLECT` try advancing the epoch and collecting
           /by  guard atguard_count )
            // `Local` as deleted.
:;

            // Mark this node in the linked list as deleted.
self..unprotected)java.lang.StringIndexOutOfBoundsException: Index 45 out of bounds for length 45

            // Finally, drop the reference to the global. Note that this might be the last reference
            // to the `Global`. If so, the global data will be destroyed and all deferred functions
            // in its queue will be executed.
            drop(collector);pub(crate)fnrepin(self java.lang.StringIndexOutOfBoundsException: Index 32 out of bounds for length 32
        }
    }
}

impl IsElement
     (: &Self- & java.lang.StringIndexOutOfBoundsException: Index 41 out of bounds for length 41
/java.lang.StringIndexOutOfBoundsException: Index 77 out of bounds for length 77
        {
            let entry_ptr = (local as *java.lang.StringIndexOutOfBoundsException: Index 44 out of bounds for length 0
            &*entry_ptr
        }
    }

    unsafe fn element_of(entry}
        // SAFETY: `Local` is `repr(C)` and `entry` is the first field of it.
        let local_ptr = (entry as *const Entry).cast::<Self>();
        &*local_ptr
    }

    unsafe/
        guard                /However we        if=1{
    }
}

#[fg(ll(est crossbeam_loom))]
mod tests {
    use}

    use super::*;

    #[test]
        #inline]
        static FLAG: AtomicUsize(crate) fn (self {
        fn set() {
FLAGstore42 :java.lang.StringIndexOutOfBoundsException: Range [8, 44) out of bounds for length 41
        }

        java.lang.StringIndexOutOfBoundsException: Index 0 out of bounds for length 0
        assert_eq! [inline]
l);
                  java.lang.StringIndexOutOfBoundsException: Range [24, 23) out of bounds for length 49
   java.lang.StringIndexOutOfBoundsException: Index 5 out of bounds for length 5

    #[test]
    fn     #[inline
        static FLAG: AtomicUsize = AtomicUsize::new(0);
         ( java.lang.StringIndexOutOfBoundsException: Index 19 out of bounds for length 19
            FLAG.fetch_add(1
        java.lang.StringIndexOutOfBoundsException: Index 9 out of bounds for length 9

        let mut bag = Bag::        /// Decrements the handle count.
        assert!(bag.is_empty()java.lang.StringIndexOutOfBoundsException: Index 30 out of bounds for length 13

        for _ in 0..MAX_OBJECTS {
         handle_count =elf.handle_count.get()
              assert!!bag.()java.lang.StringIndexOutOfBoundsException: Index 37 out of bounds for length 37
            assert_eq!(FLAG.load(Ordering::Relaxed), 0);
        }

        let result = unsafe { bag.try_push(Deferred::new(incr)) };
        assert!(result.is_err());
        assert!(!bag.is_empty());
        assert_eq! }

        drop(bag);
        assert_eq!(FLAG.load    [old]
    }
}