.


:

:



,



( , )

:

































 

 

 

 
FAQ

UNIX.

1

1

 

. V UNIX IPC (interprocess communication) :


  • ;

  • ;

  • - .


, , .

 


  • , .

  • (key), , .

  • get, ; (flag). . IPC_PRIVATE . IPC_CREAT , , IPC_EXCL, , . , , , creat open.

  • : = . , , 100 , , 1, , 1, 101, 201 .. , : , get. , , . . 1 , 201, , 301. , 201, , . , , .

  • , , , , , control ( ), - - , , .

  • , , , , ( , , ..), .

  • control, , . , , , , . , ( ), , ; . , , ( ). , , , , . , , , . , . , , , .

2

(. Spinlock ) , .

- - . - , . - , - - ( busy-waiting). , - . - , , , , .
- , , IRQL. : , IRQL PASSIVE_ LEVEL - . IRQL DISPATCH_LEVEL, -, , -, . , , - , IRQL ! , , IRQL IRQL IRQL -. IRQL - IRQL, -, IRQL . , , IRQL, , -, IRQL - IRQL . - IRQL IRQL -, .
NT -:
  • -, - /, / (. /).
  • - .

- IRQL DISPATCH_LEVEL, :

  • IRQL, DISPATCH_LEVEL;
  • - IRQL DISPATCH_LEVEL.

- DIRQL. - ( - /, ). - , .

-

  1. 1. VOID KeInitializeSpinLock(IN PKSPIN_LOCK SpinLock); KSPIN_LOCK. - .
    2. VOID KeAcquireSpinLock(IN PKSPIN_LOGK SpinLock, OUT PKIRQL Oldlrql); -. . IRQL DISPATCH_LEVEL. IRQL, ( <= DISPATCH_LEVEL).
    3. VOID KeReleaseSpinLock(IN PKSPINJLOCK SpinLock, OUT PKIRQL Newlrql); - IRQL Newlrql. , KeAcquireSpinLock() Oldlrql.
    4. VOID KeAcquireLockAtDpcLevel(IN PKSPIN_LOCK SpinLock); - , IRQL DISPATCH_LEVEL. IRQL . , IRQL.
    5. VOID KeReleaseLockFromDpcLevel(IN PKSPIN_LOCK SpinLock); - , KeAcquireLockAtDpcLevel(). .

 

-:

typedef struct _DEVICE_EXTENSION
KSPIN_LOCK spinlock }DEVICE_EXTENSION, *PDEVICE_EXTENSION;
*
NTSTATUS DriverEntry (....)
KelnitializeSpinLock(&extension->spinlock); }
NTSTATUS DispatchReadWrite(...)
{
KIRQL Oldlrql;
KeAcquireSpinLock(&extension->spinlock, &01dlrql); // , // -
KeReleaseSpinLock(&extension->spinlock, Oldlrql); }

2

 

1

(process specific). , handle , , . .

-, . ( ) .

-, . DuplicateHandle , .. , .

, , . (, , ) . . , Open(OpenMutex, OpenSemaphore, OpenWaitableTimer, OpenEvent) .

, Create... () , . , . , . , Create NULL. , (handle) . GetLastError() : Create() .

, . .

10. , . - .

 

int main(int argc, char* argv[]) { HANDLE Mutex; Mutex = CreateMutex(NULL,FALSE,"MyMutex"); if (ERROR_ALREADY_EXISTS == GetLastError()) // - ... { MessageBox(0," ","Error",0); CloseHandle(Mutex); exit(0); }... }

 

2

, , .[1] , , .

, , - , .

, Concurrent Pascal Solo.

:

,

,

, ,

, (. ). , , , .

. , .

monitor account { int balance:= 0 function withdraw(int amount) { if amount < 0 then error " " else if balance < amount then error " " else balance:= balance - amount } function deposit(int amount) { if amount < 0 then error " " else balance:= balance + amount }}

, , . , . , , D, . . , , -, .

䳿 . , , , .

9. , , . . , ' , .

, , , . , (Hoare) (Brinch Hansen) 1974 . , , , ' .

( - ) , , , . :

; .

.

; - , , .

 

, '- ' . , .

. , , . , , , . ϳ, , , .

, . :

cwait(c) c. .

csignal(c) , cwait . , ; , .

 

, cwait / csignal . , , . , , , .

( ) , , , - csignal . , csignal , .

:

, csignal , : , .

, ' , . csignal , . , ' .

(Lampson, Redell) Mesa ( Modula-3). csignal cnotify(x), .

, , cnotify(x), x, . , , . , , , , .

, - , ' cnotify. , , , , . , . , .

cbroadcast ( ), . , , . - .

- , . , .

. . ( Solaris). , , Java. synchronized , , '. , Java ', , ' .

 

3

 

1

 

- , wait signal init. 0 1. .

: , . , , , , , . , , .

, . ( ).

, .

;

( , ).

, .

semaphore.init(1); 1:semaphore.enter();cout << " : ";for (int i=0; i<n; i++) cout << a[i] << ' ';cout << '\n';semaphore.leave(); 2:semaphore.enter();cout << " Esc.\n";semaphore.leave();

: 1 2 3 Esc.4 5 6

, . , , Algol-68. , wait signal, Algol-68 down up .

,

, Modula-2. . ³ Processes . 3.7:

˳ 3.7.

DEFINITION MODULE Processes;

TYPE SIGNAL;

PROCEDURE StartProcess(P:PROC; n:CARDINAL); (* , n *)

PROCEDURE SEND(VAR s:SIGNAL); (* ³ ,

s *)

PROCEDURE WAIT(VAR s:SIGNAL); (* s *)

PROCEDURE Awaited(VAR s:SIGNAL): BOOLEAN; (* TRUE

s *)

PROCEDURE Init(VAR s:SIGNAL); (* ' *)

END Processes.

³ ' Init , Awaited.

C/C++, , , , . , MFC Microsoft CSemaphore CMutex, ' .

UNIX.

 

UNIX- POSIX (P1003.1c). , , , .

POSIX

3.2.
pthread_mutex_init '
pthread_mutex_destroy '
pthread_mutex_lock ' (. wait)
pthread_mutex_unlock ' (. signal)
sem_init
sem_wait (. wait)
sem_post (. signal)
sem_getvalue

 

2

/

/. , - . : , () ( ) ( ) , . , .

. . 3.9:

˳ 3.9.

#include <pthread.h> // POSIX-

#include <semaphore.h> // POSIX-

const int SizeOfBuffer = 64; //

pthread_t PRODUCERID, CONSUMERID; //

sem_t s; //

sem_t occupied; // ʳ

sem_t available; //

char chin, chout; //

char Buffer[SizeOfBuffer]; //

void Produce() { /* chin */ }

void Consume() { /* chout */ }

void Producer() { //

static int NextFree = 0;

while(true){

Produce(); //

sem_wait(&available); // sem_wait(&s); //

Buffer[NextFree]= chin; //

NextFree = (NextFree + 1) % SizeOfBuffer;

sem_post(&s); // ʳ

sem_post(&occupied); //

}

void Consumer() { //

static int NextChar = 0;

while(true){

sem_wait(&occupied); // sem_wait(&s); //

chout = Buffer[NextChar]; //

NextChar = (NextChar + 1) % SizeOfBuffer;

sem_post(&s); // ʳ

sem_post(&available); //

Consume(); //

}

void main() {

/* Ͳֲ˲Ӫ : */

sem_init(&s, 0, 1); //

sem_init(&occupied, 0, 0); // , sem_init(&available, 0, SizeOfBuffer); //

/* Ӫ : */

pthread_create(&PRODUCERID, NULL, Producer, NULL);

pthread_create(&CONSUMERID, NULL, Consumer, NULL);

} // , : NULL

- POSIX. ϳ Linux. ³, . , , .

 

4

1

3.9.1.

, . ( ). .

˳ 3.1.

boolean flag = false; /* */

/* 1 */ /* 2 */

while(flag); /* ײ*/ while(flag);

flag = true; flag = true;

/* IJ */ /* IJ */

flag = false; flag = false;

/* */ /* */

flag , . . . , . , , - (spinlock).

, (. 3.1.) . 1 flag, . 2, . flag, false, . , , ! , . . (T. Dekker). 1981 . (G.L. Peterson). [2].

3.9.2.

, . (. 3.2.).

˳ 3.2.

/* */;

/* */;

/* IJ */;

/* */;

/* */;

: ( ) (, ).

.

. 3.1 , , ' . - , - , ', , .

. 3.3.

˳ 3.3.

boolean testset(int i){

if(i==0){

i=1;

Return true;

}

Else

Return false;

}

(. . ). testset ' . , Pentium CMPXCHG reg/mem,reg1 ( ), : - reg1, ' reg/mem ( EAX). , -. .

. 3.4 - :

˳ 3.4.

const int n = /* */;

Int bvar;

void P(int i){

while(1){

while(!testset(bvar)); /* ײ */

/* */;

bvar = 0;

/* */;

}

void main(){

bvar = 0;

parbegin(P(1),P(2),...,P(n)); /* */

}

:

- -, .

, .

( ).

:

. .

. , , .

.

 

. 1

testset , 1 2 . 2 , . 1 , (. . ).

- . 򳺿 , - , . . Windows NT.

Windows NT - , IRQL (Interrupt ReQuest Level ). , IRQL IRQL , 䳺 -. IRQL - , -, IRQL . , IRQL, , - IRQL , .

 

2

/

/. . (, ) (), , (). ʳ , . . - , , -. ' -.

H. Ballhausen (˳. 3.10.).

˳ 3.10.

var semaphore mutex = 1; //

var semaphore access = m; //

process reader(integer i = 1... m) { // m

do {

Wait(access);

//... ...

Signal(access);

//... ...

}

}

process writer(integer j = 1... n) { // n

integer k;

do {

wait(mutex); //

for k = 1... m do wait(access); //

//

//... ...

for k = 1... m do signal(access);

signal(mutex);

//... ...

}

}

void main(){

// :

parbegin(reader(1),...,reader(m),writer(1),...,writer(n));

}

/ , .

 

5 1

 

, ( ), , . , .

, 䳿 , , [2] . 3.1.

䳿

 

3.1. 䳿
. . . . . ( ). .
. . , ( , ). . . ( ). . ' .
( ). '. , . . ( ). .

 

, . . .

:

(mutual exclusion) - , , , . , , , () (critical section). , - . :

(deadlock). , 1 2 R1 R2 . ( : P1 R1, P2 R2) .

(starvation). 1, 2, 3 . 1 2 , 3 , .

, , .

( ), , .

( ), '. ' . , ' . . , . , , . .

. , - :

.

, () , .

( ).

, - , , .

.

.

:

( ).

.

.

 

2

Mutex (thread), (process), .

:

Mutex - . , , . Mutex . CreateMutex(), OpenMutex(), ReleaseMutex(). Mutex WaitForSingleObject(). . Mutex . Mutex . , CreateMutex() , . . .

(, mutex) - , , - . , - . , , , , - . , .

( ) , CreateMutex. , . , , . , bInitialOwner FALSE, .

, . :

  • , CreateProcess , () CreateMutex lpMutexAttributes.
  • DuplicateHandle.
  • OpenMutex CreateMutex.

, , .

#include <windows.h>
#include <process.h>
#include <stdio.h>

HANDLE hMutex;
int a[ 5 ];

void Thread(void* pParams)
{
int i, num = 0;

while (TRUE)
{
WaitForSingleObject(hMutex, INFINITE);
for (i = 0; i < 5; i++) a[ i ] = num;
ReleaseMutex(hMutex);
num++;
}
}

int main(void)
{
hMutex = CreateMutex(NULL, FALSE, NULL);
_beginthread(Thread, 0, NULL);

while(TRUE)

{
WaitForSingleObject(hMutex, INFINITE);
printf("%d %d %d %d %d\n",
a[ 0 ], a[ 1 ], a[ 2 ],
a[ 3 ], a[ 4 ]);
ReleaseMutex(hMutex);
}
return 0;
}

 

<== | ==>
- 580USD |
:

: 2016-11-20; !; : 455 |

:

:

.
==> ...

1317 - | 1261 -


© 2015-2024 lektsii.org - -

: 0.216 .