diff options
| author | Frans Kaashoek <kaashoek@mit.edu> | 2020-08-10 13:05:17 -0400 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-08-10 13:05:17 -0400 |
| commit | c31d35d8031c88b7e1ea8657cc9806dfdd4c3ef9 (patch) | |
| tree | a6c903e1c61c08f4cb87700c320752a737081dcb /kernel/spinlock.c | |
| parent | 90eb90b5e203299427c3fde8c996a48835fc93cf (diff) | |
| parent | d8fe1773b26758c7c7b8f36724cd822555b33612 (diff) | |
| download | xv6-labs-c31d35d8031c88b7e1ea8657cc9806dfdd4c3ef9.tar.gz xv6-labs-c31d35d8031c88b7e1ea8657cc9806dfdd4c3ef9.tar.bz2 xv6-labs-c31d35d8031c88b7e1ea8657cc9806dfdd4c3ef9.zip | |
Merge branch 'riscv' into riscv
Diffstat (limited to 'kernel/spinlock.c')
| -rw-r--r-- | kernel/spinlock.c | 16 |
1 files changed, 9 insertions, 7 deletions
diff --git a/kernel/spinlock.c b/kernel/spinlock.c index 563532e..9840302 100644 --- a/kernel/spinlock.c +++ b/kernel/spinlock.c @@ -34,7 +34,8 @@ acquire(struct spinlock *lk) // Tell the C compiler and the processor to not move loads or stores // past this point, to ensure that the critical section's memory - // references happen after the lock is acquired. + // references happen strictly after the lock is acquired. + // On RISC-V, this emits a fence instruction. __sync_synchronize(); // Record info about lock acquisition for holding() and debugging. @@ -52,8 +53,10 @@ release(struct spinlock *lk) // Tell the C compiler and the CPU to not move loads or stores // past this point, to ensure that all the stores in the critical - // section are visible to other CPUs before the lock is released. - // On RISC-V, this turns into a fence instruction. + // section are visible to other CPUs before the lock is released, + // and that loads in the critical section occur strictly before + // the lock is released. + // On RISC-V, this emits a fence instruction. __sync_synchronize(); // Release the lock, equivalent to lk->locked = 0. @@ -69,13 +72,12 @@ release(struct spinlock *lk) } // Check whether this cpu is holding the lock. +// Interrupts must be off. int holding(struct spinlock *lk) { int r; - push_off(); r = (lk->locked && lk->cpu == mycpu()); - pop_off(); return r; } @@ -100,9 +102,9 @@ pop_off(void) struct cpu *c = mycpu(); if(intr_get()) panic("pop_off - interruptible"); - c->noff -= 1; - if(c->noff < 0) + if(c->noff < 1) panic("pop_off"); + c->noff -= 1; if(c->noff == 0 && c->intena) intr_on(); } |