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MFp4:

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The unit number allocator reuses ID too fast, this may hide bugs in
other code, add a ring buffer to delay freeing a thread ID.
This commit is contained in:
davidxu 2010-12-09 05:16:20 +00:00
parent 171976dba2
commit f88dac0410
1 changed files with 42 additions and 3 deletions
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45
sys/kern/kern_thread.c
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@ -81,15 +81,54 @@ MTX_SYSINIT(zombie_lock, &zombie_lock, "zombie lock", MTX_SPIN);
static void thread_zombie(struct thread *);
#define TID_BUFFER_SIZE 1024
struct mtx tid_lock;
static struct unrhdr *tid_unrhdr;
static lwpid_t tid_buffer[TID_BUFFER_SIZE];
static int tid_head, tid_tail;
static MALLOC_DEFINE(M_TIDHASH, "tidhash", "thread hash");
struct tidhashhead *tidhashtbl;
u_long tidhash;
struct rwlock tidhash_lock;
static lwpid_t
tid_alloc(void)
{
lwpid_t tid;
tid = alloc_unr(tid_unrhdr);
if (tid != -1)
return (tid);
mtx_lock(&tid_lock);
if (tid_head == tid_tail) {
mtx_unlock(&tid_lock);
return (-1);
}
tid = tid_buffer[tid_head++];
tid_head %= TID_BUFFER_SIZE;
mtx_unlock(&tid_lock);
return (tid);
}
static void
tid_free(lwpid_t tid)
{
lwpid_t tmp_tid = -1;
mtx_lock(&tid_lock);
if ((tid_tail + 1) % TID_BUFFER_SIZE == tid_head) {
tmp_tid = tid_buffer[tid_head++];
tid_head = (tid_head + 1) % TID_BUFFER_SIZE;
}
tid_buffer[tid_tail++] = tid;
tid_tail %= TID_BUFFER_SIZE;
mtx_unlock(&tid_lock);
if (tmp_tid != -1)
free_unr(tid_unrhdr, tmp_tid);
}
/*
* Prepare a thread for use.
*/
@ -102,7 +141,7 @@ thread_ctor(void *mem, int size, void *arg, int flags)
td->td_state = TDS_INACTIVE;
td->td_oncpu = NOCPU;
td->td_tid = alloc_unr(tid_unrhdr);
td->td_tid = tid_alloc();
/*
* Note that td_critnest begins life as 1 because the thread is not
@ -156,7 +195,7 @@ thread_dtor(void *mem, int size, void *arg)
osd_thread_exit(td);
EVENTHANDLER_INVOKE(thread_dtor, td);
free_unr(tid_unrhdr, td->td_tid);
tid_free(td->td_tid);
}
/*