Re: [9fans] syscall silently kill processes

[andrey100100100@gmail.com]

В Пн, 20/06/2022 в 15:29 -0700, Skip Tavakkolian пишет:
> It's cleaner to use channels with separate io and timer threads that
> do their syscalls via ioproc; this one doesn't require any changes to
> libthread:
> 
> https://gist.github.com/9nut/aaa9b9b6a22d69996b75ccdc6e615c61

Thanks for the work you've done!
Yes, I have considered this possibility.
But it was precisely this kind of code bloat that I wanted to avoid.

And yet, the libthread needs fixing. What adr suggested, at first
glance, is acceptable.
And it turns out that we are trying to get around the problems of the
libthread using the libthread...
By not fixing the libthread, we reduce the number of use cases for it,
which is bad.


PS. Philosophical question: should someone monitor the process or
should the process serve itself?


> 
> 
> On Mon, Jun 20, 2022 at 8:57 AM <andrey100100100@gmail.com> wrote:
> > 
> > В Пн, 20/06/2022 в 05:59 +0000, adr пишет:
> > > On Mon, 20 Jun 2022, adr wrote:
> > > > But I have something in mind for a case like
> > > > this, when all the processes are going to use the same handler
> > > > (that's why I was asking). Let me play with it a litle before I
> > > > share it.
> > > 
> > > Ok, the idea is this: If in is bigger than zero in
> > > threadnotify(int (*f)(void*, char*), int in), the handler is
> > > register
> > > for the calling process. If in is 0, then the handler is cleared
> > > for the calling process. If in is -1, the handler is register for
> > > all processes and if in is less than -1, it is cleared for all
> > > processes (expect for those who have already registered it for
> > > themselves).
> > > 
> > > Now back to your example, as all the processes are going to use
> > > the
> > > same handler,
> > > you just have to register it once in threadmain:
> > > 
> > > #include <u.h>
> > > #include <libc.h>
> > > #include <thread.h>
> > > 
> > > static int
> > > handler_alarm(void *, char *msg)
> > > {
> > >         if(strstr(msg, "alarm"))
> > >                 return 1;
> > >         return 0;
> > > }
> > > 
> > > static void
> > > proc_udp(void *)
> > > {
> > >         char resp[512];
> > >         char req[] = "request";
> > >         int fd;
> > >         if((fd = dial("udp!185.157.221.201!5678", nil, nil, nil))
> > > 0){
> > >                 if(write(fd, req, strlen(req)) == strlen(req)){
> > >                         fprint(1, "start\n");
> > >                         alarm(2000);
> > >                         read(fd, resp, sizeof(resp));
> > >                         alarm(0);
> > >                         fprint(1, "end\n");
> > >                 }
> > >                 close(fd);
> > >         }
> > >         threadexits(nil);
> > > }
> > > 
> > > int mainstacksize = 5242880;
> > > 
> > > void
> > > threadmain(int argc, char *argv[])
> > > {
> > >         threadnotify(handler_alarm, -1);
> > >         for(int i = 0; i < 80; i++)
> > >                 proccreate(proc_udp, nil, 10240);
> > >         sleep(5000);
> > >         threadexitsall(nil);
> > > }
> > > Now,
> > > ; ./5.out | grep end | wc -l
> > >       80
> > > 
> > > Are you happy Andrej?
> > 
> > 
> > Yes. Thank you very much! It's working!
> > 
> > How convenient it is to use - more experiments are needed.
> > 
> > 
> > > 
> > > adr.
> > > 
> > > /sys/src/libthread/sched.c:
> > > [...]
> > >                 if(t == nil){
> > >                         _threaddebug(DBGSCHED, "all threads gone;
> > > exiting");
> > >                         cancelnotes(p->pid);
> > >                         _schedexit(p);
> > >                 }
> > > [...]
> > > /sys/src/libthread/note.c
> > > [...]
> > > int
> > > threadnotify(int (*f)(void*, char*), int in)
> > > {
> > >         int i, frompid, topid;
> > >         int (*from)(void*, char*), (*to)(void*, char*);
> > > 
> > >         if(in && in>-2){
> > >                 from = nil;
> > >                 frompid = 0;
> > >                 to = f;
> > >                 topid = (in == -1)? -1 : _threadgetproc()->pid;
> > >                 lock(&onnotelock);
> > >                 for(i=0; i<NFN; i++)
> > >                         if(onnote[i]==to && onnotepid[i]==topid){
> > >                                 unlock(&onnotelock);
> > >                                 return i<NFN;
> > >                         }
> > >                 unlock(&onnotelock);
> > >         }else{
> > >                 from = f;
> > >                 frompid = (in < -1)? -1 : _threadgetproc()->pid;
> > >                 to = nil;
> > >                 topid = 0;
> > >         }
> > >         lock(&onnotelock);
> > >         for(i=0; i<NFN; i++)
> > >                 if(onnote[i]==from && onnotepid[i]==frompid){
> > >                         onnote[i] = to;
> > >                         onnotepid[i] = topid;
> > >                         break;
> > >                 }
> > >         unlock(&onnotelock);
> > >         return i<NFN;
> > > }
> > > 
> > > void
> > > cancelnotes(int pid)
> > > {
> > >         int i;
> > > 
> > >         lock(&onnotelock);
> > >         for(i=0; i<NFN; i++)
> > >                 if(onnotepid[i] == pid){
> > >                         onnote[i] = nil;
> > >                         onnotepid[i] = 0;
> > >                 }
> > >         unlock(&onnotelock);
> > >         return;
> > > }
> > > 
> > > static void
> > > delayednotes(Proc *p, void *v)
> > > {
> > >         int i;
> > >         Note *n;
> > >         int (*fn)(void*, char*);
> > > 
> > >         if(!p->pending)
> > >                 return;
> > > 
> > >         p->pending = 0;
> > >         for(n=notes; n<enotes; n++){
> > >                 if(n->proc == p){
> > >                         for(i=0; i<NFN; i++){
> > >                                 if((onnotepid[i]!=p->pid &&
> > > onnotepid[i]!=-1) || (fn = onnote[i])==nil)
> > >                                         continue;
> > >                                 if((*fn)(v, n->s))
> > >                                         break;
> > > [...]
> > > /sys/include/thread.h
> > > [...]
> > > void cancelnotes(int pid);
> > > [...]
> > > 

Regards,
Andrej

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