Unfortunately the changes break sysv ipc. I submitted the attached fix,
but it apparently
got lost...
Clemens
Ingo Molnar wrote:
> Changes/goals wrt. the waitqueues changes:
>
> 1) waitqueue heads were separated from waitqueue entries, data-structure
> wise. Formerly the head was a pointer, which was not generic enough, see
> later.
>
> 2) the waitqueue list has been changed to be a double-linked never-zero
> ringlist. This has obvious micro-speed and algorithmical scaling benefits,
> formerly remove_from_wait_queue() had to potentially traverse all the
> waitqueue to remove a single entry. Now it's all O(1).
>
> 3) the generic datastructures enabled us to add per-waitqueue spinlocks
> which makes us scale better on SMP. Particularly __wake_up() tends to hold
> the waitqueue lock while doing other stuff (well, waking up processes), so
> this is a definit win. It was also easy and seemless due to the generic
> data structures. The spinlock architecture is atm. 'dual', which means
> that it can be switched between readwrite and 'simple' spinlocks via a
> define. The 'simple' version was benchmarked to perform better, that one
> will probably stick and the rw-version will be removed.
>
> 4) all these changes enabled to implement the primary goal that triggered
> all these changes and cleanups: it was possible to add wake-one semantics
> for wakeup() in a clean way. (see the TASK_EXCLUSIVE stuff)
>
> compiler_warning is there to make old code generate more warning messages
> when you old-style initialize waitqueues.
>
> the debugging stuff will be removed before 2.4 - the frequency of
> waitqueue-related bugs is already very low. There is still some small
> benchmarking work to be done wrt. the wakeup order of exclusive tasks.
>
> -- mingo
>
> -
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> Please read the FAQ at http://www.tux.org/lkml/
--------------1DE36E6A8B7E5DC0892CF784
Content-Type: text/plain; charset=us-ascii;
name="diff.ipc"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
filename="diff.ipc"
diff -ur linux/include/linux/msg.h linux.new/include/linux/msg.h
--- linux/include/linux/msg.h Sat May 15 16:34:43 1999
+++ linux.new/include/linux/msg.h Sat May 29 21:03:42 1999
@@ -27,6 +27,25 @@
__kernel_ipc_pid_t msg_lspid; /* pid of last msgsnd */
__kernel_ipc_pid_t msg_lrpid; /* last receive pid */
};
+/* to keep compatibility with ipc msgctl syscall, keep old msqid_ds
+ struct */
+struct msqid_u_ds
+{
+ struct ipc_perm msg_perm;
+ struct msg *__msg_first;
+ struct msg *__msg_last;
+ __kernel_time_t msg_stime;
+ __kernel_time_t msg_rtime;
+ __kernel_time_t msg_ctime;
+ void *__wwait; /* not transmitted to userland */
+ void *__rwait; /* not transmitted to userland */
+ unsigned short int msg_cbytes;
+ unsigned short int msg_qnum;
+ unsigned short int msg_qbytes;
+ __kernel_ipc_pid_t msg_lspid;
+ __kernel_ipc_pid_t msg_lrpid;
+};
+
/* message buffer for msgsnd and msgrcv calls */
struct msgbuf {
@@ -73,7 +92,7 @@
asmlinkage int sys_msgsnd (int msqid, struct msgbuf *msgp, size_t msgsz, int msgflg);
asmlinkage int sys_msgrcv (int msqid, struct msgbuf *msgp, size_t msgsz, long msgtyp,
int msgflg);
-asmlinkage int sys_msgctl (int msqid, int cmd, struct msqid_ds *buf);
+asmlinkage int sys_msgctl (int msqid, int cmd, struct msqid_u_ds *buf);
#endif /* __KERNEL__ */
diff -ur linux/ipc/msg.c linux.new/ipc/msg.c
--- linux/ipc/msg.c Sat May 29 16:50:49 1999
+++ linux.new/ipc/msg.c Sat May 29 19:41:39 1999
@@ -352,11 +352,11 @@
kfree(msq);
}
-asmlinkage int sys_msgctl (int msqid, int cmd, struct msqid_ds *buf)
+asmlinkage int sys_msgctl (int msqid, int cmd, struct msqid_u_ds *buf)
{
int id, err = -EINVAL;
struct msqid_ds *msq;
- struct msqid_ds tbuf;
+ struct msqid_u_ds tbuf;
struct ipc_perm *ipcp;
printk("msgctl: %d %d %p\n",msqid,cmd,buf);
--------------1DE36E6A8B7E5DC0892CF784--
-
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