diff options
author | Frans Kaashoek <[email protected]> | 2016-09-08 21:20:26 -0400 |
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committer | Frans Kaashoek <[email protected]> | 2016-09-08 21:20:26 -0400 |
commit | 551c2f3576d34e4749a1165af07d90e21ad528be (patch) | |
tree | 7fac220585c88fcb568bc8c656e0532b033fec9b | |
parent | 1b8ccf9482facb15f905a6baca4f5d800a13c542 (diff) | |
parent | 34c2efc1d063f4b366c1017c174d117cc96eb990 (diff) | |
download | xv6-labs-551c2f3576d34e4749a1165af07d90e21ad528be.tar.gz xv6-labs-551c2f3576d34e4749a1165af07d90e21ad528be.tar.bz2 xv6-labs-551c2f3576d34e4749a1165af07d90e21ad528be.zip |
Merge branch 'master' of g.csail.mit.edu:xv6-dev
-rw-r--r-- | proc.c | 18 | ||||
-rw-r--r-- | spinlock.c | 6 |
2 files changed, 21 insertions, 3 deletions
@@ -82,6 +82,12 @@ userinit(void) acquire(&ptable.lock); p = allocproc(); + + // release the lock in case namei() sleeps. + // the lock isn't needed because no other + // thread will look at an EMBRYO proc. + release(&ptable.lock); + initproc = p; if((p->pgdir = setupkvm()) == 0) panic("userinit: out of memory?"); @@ -99,6 +105,12 @@ userinit(void) safestrcpy(p->name, "initcode", sizeof(p->name)); p->cwd = namei("/"); + // this assignment to p->state lets other cores + // run this process. the acquire forces the above + // writes to be visible, and the lock is also needed + // because the assignment might not be atomic. + acquire(&ptable.lock); + p->state = RUNNABLE; release(&ptable.lock); @@ -141,6 +153,8 @@ fork(void) return -1; } + release(&ptable.lock); + // Copy process state from p. if((np->pgdir = copyuvm(proc->pgdir, proc->sz)) == 0){ kfree(np->kstack); @@ -165,6 +179,8 @@ fork(void) pid = np->pid; + acquire(&ptable.lock); + np->state = RUNNABLE; release(&ptable.lock); @@ -227,7 +243,7 @@ wait(void) acquire(&ptable.lock); for(;;){ - // Scan through table looking for zombie children. + // Scan through table looking for exited children. havekids = 0; for(p = ptable.proc; p < &ptable.proc[NPROC]; p++){ if(p->parent != proc) @@ -59,8 +59,10 @@ release(struct spinlock *lk) // stores; __sync_synchronize() tells them both to not re-order. __sync_synchronize(); - // Release the lock. - lk->locked = 0; + // Release the lock, equivalent to lk->locked = 0. + // This code can't use a C assignment, since it might + // not be atomic. + asm volatile("movl $0, %0" : "+m" (lk->locked) : ); popcli(); } |