157 lines
4.3 KiB
C
157 lines
4.3 KiB
C
/*++
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Copyright (c) 1991 Microsoft Corporation
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Module Name:
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tcpip\ip\ipmlock.h
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Abstract:
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Reader Writer lock primitives for the IP Multicasting
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Author:
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Amritansh Raghav
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Revision History:
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AmritanR Created
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Notes:
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--*/
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//
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// Need to include "debug.h" before this file is included because
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// RT_LOCK is defined there
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//
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//
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// A reader writer lock for kernel mode.
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//
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typedef struct _RW_LOCK
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{
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RT_LOCK rlReadLock;
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RT_LOCK rlWriteLock;
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LONG lReaderCount;
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}RW_LOCK, *PRW_LOCK;
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//
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// VOID
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// InitRwLock(
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// PRW_LOCK pLock
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// )
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//
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// Initializes the spin locks and the reader count
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//
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#define InitRwLock(l) \
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RtInitializeSpinLock(&((l)->rlReadLock)); \
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RtInitializeSpinLock(&((l)->rlWriteLock)); \
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(l)->lReaderCount = 0
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//
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// VOID
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// EnterReader(
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// PRW_LOCK pLock,
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// PKIRQL pCurrIrql
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// )
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//
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// Acquires the Reader Spinlock (now thread is at DPC).
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// InterlockedIncrements the reader count (interlocked because the reader
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// lock is not taken when the count is decremented in ExitReader())
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// If the thread is the first reader, also acquires the Writer Spinlock (at
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// DPC to be more efficient) to block writers
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// Releases the Reader Spinlock from DPC, so that it remains at DPC
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// for the duration of the lock being held
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//
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// If a writer is in the code, the first reader will wait on the Writer
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// Spinlock and all subsequent readers will wait on the Reader Spinlock
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// If a reader is in the code and is executing the EnterReader, then a new
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// reader will wait for sometime on the Reader Spinlock, and then proceed
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// on to the code (at DPC)
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//
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#define EnterReader(l, q) \
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RtAcquireSpinLock(&((l)->rlReadLock), (q)); \
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if(InterlockedIncrement(&((l)->lReaderCount)) == 1) \
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RtAcquireSpinLockAtDpcLevel(&((l)->rlWriteLock)); \
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RtReleaseSpinLockFromDpcLevel(&((l)->rlReadLock))
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#define EnterReaderAtDpcLevel(l) \
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RtAcquireSpinLockAtDpcLevel(&((l)->rlReadLock)); \
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if(InterlockedIncrement(&((l)->lReaderCount)) == 1) \
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RtAcquireSpinLockAtDpcLevel(&((l)->rlWriteLock)); \
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RtReleaseSpinLockFromDpcLevel(&((l)->rlReadLock))
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//
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// VOID
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// ExitReader(
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// PRW_LOCK pLock,
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// KIRQL kiOldIrql
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// )
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//
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// InterlockedDec the reader count.
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// If this is the last reader, then release the Writer Spinlock to let
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// other writers in
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// Otherwise, just lower the irql to what was before the lock was
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// acquired. Either way, the irql is down to original irql
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//
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#define ExitReader(l, q) \
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if(InterlockedDecrement(&((l)->lReaderCount)) == 0) \
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RtReleaseSpinLock(&((l)->rlWriteLock), q); \
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else \
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KeLowerIrql(q)
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#define ExitReaderFromDpcLevel(l) \
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if(InterlockedDecrement(&((l)->lReaderCount)) == 0) \
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RtReleaseSpinLockFromDpcLevel(&((l)->rlWriteLock))
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//
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// EnterWriter(
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// PRW_LOCK pLock,
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// PKIRQL pCurrIrql
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// )
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//
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// Acquire the reader and then the writer spin lock
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// If there are readers in the code, the first writer will wait
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// on the Writer Spinlock. All other writers will wait (with readers)
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// on the Reader Spinlock
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// If there is a writer in the code then a new writer will wait on
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// the Reader Spinlock
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#define EnterWriter(l, q) \
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RtAcquireSpinLock(&((l)->rlReadLock), (q)); \
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RtAcquireSpinLockAtDpcLevel(&((l)->rlWriteLock))
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#define EnterWriterAtDpcLevel(l) \
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RtAcquireSpinLockAtDpcLevel(&((l)->rlReadLock)); \
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RtAcquireSpinLockAtDpcLevel(&((l)->rlWriteLock))
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//
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// ExitWriter(
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// PRW_LOCK pLock,
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// KIRQL kiOldIrql
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// )
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//
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// Release both the locks
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//
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#define ExitWriter(l, q) \
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RtReleaseSpinLockFromDpcLevel(&((l)->rlWriteLock)); \
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RtReleaseSpinLock(&((l)->rlReadLock), q)
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#define ExitWriterFromDpcLevel(l) \
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RtReleaseSpinLockFromDpcLevel(&((l)->rlWriteLock)); \
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RtReleaseSpinLockFromDpcLevel(&((l)->rlReadLock))
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