Re: [9fans] syscall silently kill processes

[Skip Tavakkolian <skip.tavakkolian@gmail.com>]

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


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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