[9fans] crash on big images

[erik quanstrom]

when viewing large images on a real plan 9 terminal,
i commonly see ilock deadlocks  for example:

acid: src(0xf01b9432)
/sys/src/9/port/alloc.c:104
 99     {
 100            Private *pv;
 101    
 102            pv = p->private;
 103            ilock(&pv->lk);
>104            pv->lk.pc = getcallerpc(&p);
 105            pv->msg[0] = 0;
 106    }
 107    
 108    static void
 109    punlock(Pool *p)
acid: src(0xf01ee456)
/sys/src/libc/port/pool.c:1221
 1216   void*
 1217   poolalloc(Pool *p, ulong n)
 1218   {
 1219           void *v;
 1220   
>1221           p->lock(p);
 1222           paranoia {
 1223                   poolcheckl(p);
 1224           }
 1225           verbosity {
 1226                   pooldumpl(p);

i'm not really sure what's going on.

- erik