Synchronous C + WCRT Algebra 101 Reinhard von Hanxleden Joint work with Michael Mendler, Claus Traulsen, . . . Real-Time and Embedded Systems Group (RTSYS) Department of Computer Science Christian-Albrechts-Universit¨ at zu Kiel www.informatik.uni-kiel.de/rtsys SYNCHRON 2011, Le Bois du Lys
SC Basics Synchronous C An Alternative SC Syntax WCRT Algebra Summary Overview Synchronous C SC Basics An Alternative SC Syntax Summary WCRT Algebra v. Hanxleden, Mendler, Traulsen Synchronous C + WCRT Algebra 101 Slide 2
SC Basics Synchronous C An Alternative SC Syntax WCRT Algebra Summary The SC-Story From Last Time How to get deterministic concurrency? ◮ Deterministic decision on when to perform context switch ◮ Deterministic decision on what thread to switch to Idea: Cooperative thread scheduling at application level ◮ As in co-routines, threads decide when to resume another thread (static) ◮ However, a dispatcher decides what thread to resume (dynamic) ◮ Reactive control flow implemented at application level—are still executing a sequential C program! v. Hanxleden, Mendler, Traulsen Synchronous C + WCRT Algebra 101 Slide 3
Producer Consumer Observer int main() { int main() { int main() { DEAD(28); DEAD(41); DEAD(41); volatile unsigned int * buf = volatile unsigned int * buf = volatile unsigned int * buf = (unsigned int*)(0x3F800200); (unsigned int*)(0x3F800200); (unsigned int*)(0x3F800200); unsigned int i = 0; unsigned int i = 0; volatile unsigned int * fd = for (i = 0; ; i++ ) { int arr[8]; (unsigned int*)(0x80000600); DEAD(26); for (i =0; i<8; i++) unsigned int i = 0; *buf = i; arr[i] = 0; for (i = 0; ; i++ ) { } for (i = 0; ; i++) { DEAD(26); return 0; DEAD(26); *fd = *buf; } register int tmp = *buf; } arr[i%8] = tmp; return 0; } } return 0; } Lickly et al. , Predictable Programming on a Precision Timed Architecture , CASES’08 14 // == TICK FUNCTION == 31 Consumer: 15 int tick () 32 for (j = 0; j < 8; j++) 1 #include ”sc.h” 16 { 33 arr [ j ] = 0; 2 17 static int BUF, fd, i , j , 34 for (j = 0; ; j++) { 3 // == MAIN FUNCTION == 18 k = 0, tmp, arr [8]; 35 PAUSE; 4 int main() 19 36 tmp = BUF; 5 { 20 TICKSTART(1); 37 arr [ j % 8] = tmp; } 6 int notDone; 21 38 7 22 PCO: 39 Observer: 8 do { 23 FORK(Producer, 3); 40 for ( ; ; ) { 9 notDone = tick(); 24 FORK(Consumer, 2); 41 PAUSE; 10 //sleep(1); 25 FORKE(Observer); 42 fd = BUF; 11 } while (notDone); 26 43 k++; } 12 return 0; 27 Producer: 44 13 } 28 for (i = 0; ; i++) { 45 TICKEND; 29 PAUSE; 46 } 30 BUF = i; }
Producer Consumer Observer int main() { int main() { int main() { DEAD(28); DEAD(41); DEAD(41); volatile unsigned int * buf = volatile unsigned int * buf = volatile unsigned int * buf = (unsigned int*)(0x3F800200); (unsigned int*)(0x3F800200); (unsigned int*)(0x3F800200); unsigned int i = 0; unsigned int i = 0; volatile unsigned int * fd = for (i = 0; ; i++ ) { int arr[8]; (unsigned int*)(0x80000600); DEAD(26); for (i =0; i<8; i++) unsigned int i = 0; *buf = i; arr[i] = 0; for (i = 0; ; i++ ) { } for (i = 0; ; i++) { DEAD(26); return 0; DEAD(26); *fd = *buf; } register int tmp = *buf; } arr[i%8] = tmp; return 0; } } return 0; } Lickly et al. , Predictable Programming on a Precision Timed Architecture , CASES’08 14 // == TICK FUNCTION == 31 Consumer: 15 int tick () 32 for (j = 0; j < 8; j++) 1 #include ”sc.h” 16 { 33 arr [ j ] = 0; 2 17 static int BUF, fd, i , j , 34 for (j = 0; ; j++) { 3 // == MAIN FUNCTION == 18 k = 0, tmp, arr [8]; 35 PAUSE; 4 int main() 19 36 tmp = BUF; 5 { 20 TICKSTART(1); 37 arr [ j % 8] = tmp; } 6 int notDone; 21 38 7 22 PCO: 39 Observer: 8 do { 23 FORK(Producer, 3); 40 for ( ; ; ) { 9 notDone = tick(); 24 FORK(Consumer, 2); 41 PAUSE; 10 //sleep(1); 25 FORKE(Observer); 42 fd = BUF; 11 } while (notDone); 26 43 k++; } 12 return 0; 27 Producer: 44 13 } 28 for (i = 0; ; i++) { 45 TICKEND; 29 PAUSE; 46 } 30 BUF = i; }
Producer Consumer Observer int main() { int main() { int main() { DEAD(28); DEAD(41); DEAD(41); volatile unsigned int * buf = volatile unsigned int * buf = volatile unsigned int * buf = (unsigned int*)(0x3F800200); (unsigned int*)(0x3F800200); (unsigned int*)(0x3F800200); unsigned int i = 0; unsigned int i = 0; volatile unsigned int * fd = for (i = 0; ; i++ ) { int arr[8]; (unsigned int*)(0x80000600); DEAD(26); for (i =0; i<8; i++) unsigned int i = 0; *buf = i; arr[i] = 0; for (i = 0; ; i++ ) { } for (i = 0; ; i++) { DEAD(26); return 0; DEAD(26); *fd = *buf; } register int tmp = *buf; } arr[i%8] = tmp; return 0; } } return 0; } Lickly et al. , Predictable Programming on a Precision Timed Architecture , CASES’08 14 // == TICK FUNCTION == 31 Consumer: 15 int tick () 32 for (j = 0; j < 8; j++) 1 #include ”sc.h” 16 { 33 arr [ j ] = 0; 2 17 static int BUF, fd, i , j , 34 for (j = 0; ; j++) { 3 // == MAIN FUNCTION == 18 k = 0, tmp, arr [8]; 35 PAUSE; 4 int main() 19 36 tmp = BUF; 5 { 20 TICKSTART(1); 37 arr [ j % 8] = tmp; } 6 int notDone; 21 38 7 22 PCO: 39 Observer: 8 do { 23 FORK(Producer, 3); 40 for ( ; ; ) { 9 notDone = tick(); 24 FORK(Consumer, 2); 41 PAUSE; 10 //sleep(1); 25 FORKE(Observer); 42 fd = BUF; 11 } while (notDone); 26 43 k++; } 12 return 0; 27 Producer: 44 13 } 28 for (i = 0; ; i++) { 45 TICKEND; 29 PAUSE; 46 } 30 BUF = i; }
Producer-Consumer-Observer in SC 1 int tick () 2 { 3 static int BUF, fd, i , j , 4 k = 0, tmp, arr [8]; 5 6 TICKSTART(1); 7 8 PCO: 9 FORK(Producer, 3); 25 Observer: 10 FORK(Consumer, 2); 26 for ( ; ; ) { 11 FORKE(Observer); 27 PAUSE; 12 28 fd = BUF; 13 Producer: 29 k++; } 14 for (i = 0; ; i++) { 30 15 PAUSE; 31 TICKEND; 16 BUF = i; } 32 } 17 18 Consumer: 19 for (j = 0; j < 8; j++) 20 arr [ j ] = 0; 21 for (j = 0; ; j++) { 22 PAUSE; 23 tmp = BUF; 24 arr [ j % 8] = tmp; }
Producer-Consumer-Observer + Preemptions 1 int tick () 2 { 3 static int BUF, fd, i , j , 4 k = 0, tmp, arr [8]; 5 6 TICKSTART(1); 7 8 PCO: 9 FORK(Producer, 3); 25 Observer: 10 FORK(Consumer, 2); 26 for ( ; ; ) { 11 FORKE(Observer); 27 PAUSE; 12 28 fd = BUF; 13 Producer: 29 k++; } 14 for (i = 0; ; i++) { 30 15 PAUSE; 31 TICKEND; 16 BUF = i; } 32 } 17 18 Consumer: 19 for (j = 0; j < 8; j++) 20 arr [ j ] = 0; 21 for (j = 0; ; j++) { 22 PAUSE; 23 tmp = BUF; 24 arr [ j % 8] = tmp; }
Producer-Consumer-Observer + Preemptions in SC 1 int tick () 2 { 3 static int BUF, fd, i , j , 4 k = 0, tmp, arr [8]; 26 Observer: 5 27 for ( ; ; ) { 6 TICKSTART(1); 28 fd = BUF; 7 29 k++; 8 PCO: 30 PAUSE; } 9 FORK(Producer, 4); 31 10 FORK(Consumer, 3); 32 Parent: 11 FORK(Observer, 2); 33 while (1) { 12 FORKE(Parent); 34 if (k == 20) 13 35 TRANS(Done); 14 Producer: 36 if (BUF == 10) 15 for (i = 0; ; i++) { 37 TRANS(PCO); 16 BUF = i; 38 PAUSE; 17 PAUSE; } 39 } 18 40 19 Consumer: 41 Done: 20 for (j = 0; j < 8; j++) 42 TERM; 21 arr [ j ] = 0; 43 TICKEND; 22 for (j = 0; ; j++) { 44 } 23 tmp = BUF; 24 arr [ j % 8] = tmp; 25 PAUSE; }
Going on the Road . . .
SC Basics Synchronous C An Alternative SC Syntax WCRT Algebra Summary Criticisms of Original SC ◮ Hard to understand what’s going on ◮ Thread structure gets lost ◮ What does FORK/FORKE mean? v. Hanxleden, Mendler, Traulsen Synchronous C + WCRT Algebra 101 Slide 11
SC Basics Synchronous C An Alternative SC Syntax WCRT Algebra Summary Proposed Alternative Syntax ◮ Replace labels by explicit “Thread” and “State” declarations ◮ Add syntactic scopes (braces) ◮ Predefined FORK1/FORK2/. . . operators v. Hanxleden, Mendler, Traulsen Synchronous C + WCRT Algebra 101 Slide 12
Original PCO-Example 1 int tick () 2 { 3 static int BUF, fd, i , j , 4 k = 0, tmp, arr [8]; 26 Observer: 5 27 for ( ; ; ) { 6 TICKSTART(1); 28 fd = BUF; 7 29 k++; 8 PCO: 30 PAUSE; } 9 FORK(Producer, 4); 31 10 FORK(Consumer, 3); 32 Parent: 11 FORK(Observer, 2); 33 while (1) { 12 FORKE(Parent); 34 if (k == 20) 13 35 TRANS(Done); 14 Producer: 36 if (BUF == 10) 15 for (i = 0; ; i++) { 37 TRANS(PCO); 16 BUF = i; 38 PAUSE; 17 PAUSE; } 39 } 18 40 19 Consumer: 41 Done: 20 for (j = 0; j < 8; j++) 42 TERM; 21 arr [ j ] = 0; 43 TICKEND; 22 for (j = 0; ; j++) { 44 } 23 tmp = BUF; 24 arr [ j % 8] = tmp; 25 PAUSE; }
Transforming the PCO-Example (1) 1. Separate threads 1 int tick () 25 Producer: 2 { 26 for (i = 0; ; i++) { 3 static int BUF, fd, i , j , 27 BUF = i; 4 k = 0, tmp, arr [8]; 28 PAUSE; } 5 29 6 TICKSTART(1); 30 Consumer: 7 31 for (j = 0; j < 8; j++) 8 PCO: 32 arr [ j ] = 0; 9 FORK(Producer, 4); 33 for (j = 0; ; j++) { 10 FORK(Consumer, 3); 34 tmp = BUF; 11 FORK(Observer, 2); 35 arr [ j % 8] = tmp; 12 FORKE(Parent); 36 PAUSE; } 13 37 14 Parent: 38 Observer: 15 while (1) { 39 for ( ; ; ) { 16 if (k == 20) 40 fd = BUF; 17 TRANS(Done); 41 k++; 18 if (BUF == 10) 42 PAUSE; } 19 TRANS(PCO); 43 20 PAUSE; 44 TICKEND; 21 } 45 } 22 23 Done: 24 TERM;
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