0.11的make_request
大家好！我读0.11kernel/blk_drv/ll_rw_blk.c的时候有点疑问：
这里查找的时候没有关中，如果这个时候被中断，在别的任务里面做了修改，肯定会对本任务的查找有影响啊。比如，找到一个空slot，结果中断，另一任务中也找到该slot并且修改该slot，等调度回来的时候不就崩了吗？
static void make_request(int major,int rw, struct buffer_head * bh)
{
struct request * req;
int rw_ahead;
/* WRITEA/READA is special case - it is not really needed, so if the */
/* buffer is locked, we just forget about it, else it's a normal read */
if (rw_ahead = (rw == READA || rw == WRITEA)) {
if (bh->b_lock)
return;
if (rw == READA)
rw = READ;
else
rw = WRITE;
}
if (rw!=READ && rw!=WRITE)
panic("Bad block dev command, must be R/W/RA/WA");
lock_buffer(bh);
if ((rw == WRITE && !bh->b_dirt) || (rw == READ && bh->b_uptodate)) {
unlock_buffer(bh);
return;
}
repeat:
/* we don't allow the write-requests to fill up the queue completely:
* we want some room for reads: they take precedence. The last third
* of the requests are only for reads.
*/
if (rw == READ)
req = request+NR_REQUEST;
else
req = request+((NR_REQUEST*2)/3);
/* find an empty request */
while (--req >= request)
if (req->dev<0)
break;
/* if none found, sleep on new requests: check for rw_ahead */
if (req < request) {
if (rw_ahead) {
unlock_buffer(bh);
return;
}
sleep_on(&wait_for_request);
goto repeat;
}
/* fill up the request-info, and add it to the queue */
req->dev = bh->b_dev;
req->cmd = rw;
req->errors=0;
req->sector = bh->b_blocknr<<1;
req->nr_sectors = 2;
req->buffer = bh->b_data;
req->waiting = NULL;
req->bh = bh;
req->next = NULL;
add_request(major+blk_dev,req);
}
Re: 0.11的make_request
0.11的内核代码应该不会被抢占吧大家好！
我读0.11kernel/blk_drv/ll_rw_blk.c的时候有点疑问：
这里查找的时候没有关中，如果这个时候被中断，在别的任务里面做了修改，肯定会对本任务的查找有影响啊。比如，找到一个空slot，结果中断，另一任务中也找到该slot并且修改该slot，等调度回来的时候不就崩了吗？
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