diff options
Diffstat (limited to 'spinlock.c')
| -rw-r--r-- | spinlock.c | 95 |
1 files changed, 29 insertions, 66 deletions
@@ -5,6 +5,7 @@ #include "memlayout.h" #include "spinlock.h" #include "riscv.h" +#include "proc.h" #include "defs.h" void @@ -15,27 +16,6 @@ initlock(struct spinlock *lk, char *name) lk->cpu = 0; } -void -acquire(struct spinlock *lk) -{ - lk->locked = 1; - lk->cpu = mycpu(); -} - -void -release(struct spinlock *lk) -{ - lk->locked = 0; - lk->cpu = 0; -} - -int -holding(struct spinlock *lk) -{ - return lk->locked && lk->cpu == mycpu(); -} - -#if 0 // Acquire the lock. // Loops (spins) until the lock is acquired. // Holding a lock for a long time may cause @@ -43,12 +23,14 @@ holding(struct spinlock *lk) void acquire(struct spinlock *lk) { - pushcli(); // disable interrupts to avoid deadlock. + push_off(); // disable interrupts to avoid deadlock. if(holding(lk)) panic("acquire"); // The xchg is atomic. - while(xchg(&lk->locked, 1) != 0) + //while(xchg(&lk->locked, 1) != 0) + // ; + while(__sync_lock_test_and_set(&lk->locked, 1) != 0) ; // Tell the C compiler and the processor to not move loads or stores @@ -58,7 +40,6 @@ acquire(struct spinlock *lk) // Record info about lock acquisition for holding() and debugging. lk->cpu = mycpu(); - getcallerpcs(&lk, lk->pcs); } // Release the lock. @@ -68,7 +49,6 @@ release(struct spinlock *lk) if(!holding(lk)) panic("release"); - lk->pcs[0] = 0; lk->cpu = 0; // Tell the C compiler and the processor to not move loads or stores @@ -81,27 +61,10 @@ release(struct spinlock *lk) // Release the lock, equivalent to lk->locked = 0. // This code can't use a C assignment, since it might // not be atomic. A real OS would use C atomics here. - asm volatile("movl $0, %0" : "+m" (lk->locked) : ); + //asm volatile("movl $0, %0" : "+m" (lk->locked) : ); + __sync_lock_release(&lk->locked); - popcli(); -} - -// Record the current call stack in pcs[] by following the %ebp chain. -void -getcallerpcs(void *v, uint64 pcs[]) -{ - uint64 *ebp; - int i; - - asm volatile("mov %%rbp, %0" : "=r" (ebp)); - for(i = 0; i < 10; i++){ - if(ebp == 0 || ebp < (uint64*)KERNBASE || ebp == (uint64*)0xffffffff) - break; - pcs[i] = ebp[1]; // saved %eip - ebp = (uint64*)ebp[0]; // saved %ebp - } - for(; i < 10; i++) - pcs[i] = 0; + pop_off(); } // Check whether this cpu is holding the lock. @@ -109,37 +72,37 @@ int holding(struct spinlock *lk) { int r; - pushcli(); + push_off(); r = lk->locked && lk->cpu == mycpu(); - popcli(); + pop_off(); return r; } - -// Pushcli/popcli are like cli/sti except that they are matched: -// it takes two popcli to undo two pushcli. Also, if interrupts -// are off, then pushcli, popcli leaves them off. +// push_off/pop_off are like intr_off()/intr_on() except that they are matched: +// it takes two pop_off to undo two push_off. Also, if interrupts +// are initially off, then push_off, pop_off leaves them off. void -pushcli(void) +push_off(void) { - int eflags; + struct cpu *c = mycpu(); + int old = intr_get(); - eflags = readeflags(); - cli(); - if(mycpu()->ncli == 0) - mycpu()->intena = eflags & FL_IF; - mycpu()->ncli += 1; + intr_off(); + if(c->noff == 0) + c->intena = old; + c->noff += 1; } void -popcli(void) +pop_off(void) { - if(readeflags()&FL_IF) - panic("popcli - interruptible"); - if(--mycpu()->ncli < 0) - panic("popcli"); - if(mycpu()->ncli == 0 && mycpu()->intena) - sti(); + struct cpu *c = mycpu(); + if(intr_get()) + panic("pop_off - interruptible"); + c->noff -= 1; + if(c->noff < 0) + panic("pop_off"); + if(c->noff == 0 && c->intena) + intr_on(); } -#endif |