Further optimize poll() on Windows

Author: jart

libc/calls/park.c

@@ -57,7 +57,7 @@ textwindows static int _park_thread(uint32_t msdelay, sigset_t waitmask,
   CloseHandle(sigev);
 
   // recursion is now safe
-  if (ws == -1)
+  if (ws == -1u)
     return __winerr();
   int handler_was_called = 0;
   if (sig)

libc/calls/poll-nt.c

@@ -17,6 +17,7 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/internal.h"
+#include "libc/calls/sig.internal.h"
 #include "libc/calls/state.internal.h"
 #include "libc/calls/struct/sigset.h"
 #include "libc/calls/struct/sigset.internal.h"
@@ -25,6 +26,7 @@
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/intrin/atomic.h"
 #include "libc/intrin/fds.h"
+#include "libc/intrin/weaken.h"
 #include "libc/macros.h"
 #include "libc/nt/console.h"
 #include "libc/nt/enum/filetype.h"
@@ -41,6 +43,7 @@
 #include "libc/sock/internal.h"
 #include "libc/sock/struct/pollfd.h"
 #include "libc/sysv/consts/o.h"
+#include "libc/sysv/consts/sicode.h"
 #include "libc/sysv/errfuns.h"
 #include "libc/thread/posixthread.internal.h"
 #ifdef __x86_64__
@@ -84,7 +87,7 @@ textwindows static int sys_poll_nt_actual(struct pollfd *fds, uint64_t nfds,
   struct PosixThread *pt;
   int i, rc, ev, kind, gotsocks;
   struct sys_pollfd_nt sockfds[64];
-  uint32_t cm, fi, wi, sn, pn, avail, waitfor, already_slept;
+  uint32_t cm, fi, sn, pn, avail, waitfor, already_slept;
 
   // ensure revents is cleared
   for (i = 0; i < nfds; ++i)
@@ -228,22 +231,36 @@ textwindows static int sys_poll_nt_actual(struct pollfd *fds, uint64_t nfds,
     // this ensures low latency for apps like emacs which with no sock
     // here we shall actually report that something can be written too
     if (!already_slept) {
-      if (__sigcheck(waitmask, false))
-        return -1;
+      intptr_t sigev;
+      if (!(sigev = CreateEvent(0, 0, 0, 0)))
+        return __winerr();
+      filehands[pn] = sigev;
       pt = _pthread_self();
-      filehands[pn] = pt->pt_event = CreateEvent(0, 0, 0, 0);
+      pt->pt_event = sigev;
+      pt->pt_blkmask = waitmask;
       atomic_store_explicit(&pt->pt_blocker, PT_BLOCKER_EVENT,
                             memory_order_release);
-      wi = WaitForMultipleObjects(pn + 1, filehands, 0, waitfor);
+      //!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!//
+      int sig = 0;
+      uint32_t wi = pn;
+      if (!_is_canceled() &&
+          !(_weaken(__sig_get) && (sig = _weaken(__sig_get)(waitmask))))
+        wi = WaitForMultipleObjects(pn + 1, filehands, 0, waitfor);
+      //!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!/!//
       atomic_store_explicit(&pt->pt_blocker, 0, memory_order_release);
-      CloseHandle(filehands[pn]);
-      if (wi == -1u) {
+      CloseHandle(sigev);
+      if (wi == -1u)
         // win32 wait failure
         return __winerr();
-      } else if (wi == pn) {
+      if (wi == pn) {
         // our signal event was signalled
-        if (__sigcheck(waitmask, false))
+        int handler_was_called = 0;
+        if (sig)
+          handler_was_called = _weaken(__sig_relay)(sig, SI_KERNEL, waitmask);
+        if (_check_cancel() == -1)
           return -1;
+        if (handler_was_called)
+          return eintr();
       } else if ((wi ^ kNtWaitAbandoned) < pn) {
         // this is possibly because a process or thread was killed
         fds[fileindices[wi ^ kNtWaitAbandoned]].revents = POLLERR_;
@@ -287,8 +304,6 @@ textwindows static int sys_poll_nt_actual(struct pollfd *fds, uint64_t nfds,
       } else {
         // should only be possible on kNtWaitTimeout or semaphore abandoned
         // keep looping for events and we'll catch timeout when appropriate
-        if (__sigcheck(waitmask, false))
-          return -1;
       }
     }
 
@@ -306,6 +321,13 @@ textwindows static int sys_poll_nt_impl(struct pollfd *fds, uint64_t nfds,
   uint32_t waitms;
   int i, n, rc, got = 0;
 
+  // we normally don't check for signals until we decide to wait, since
+  // it's nice to have functions like write() be unlikely to EINTR, but
+  // ppoll is a function where users are surely thinking about signals,
+  // since ppoll actually allows them to block signals everywhere else.
+  if (__sigcheck(waitmask, false))
+    return -1;
+
   // fast path
   if (nfds <= 63)
     return sys_poll_nt_actual(fds, nfds, deadline, waitmask);

libc/calls/pselect.c

@@ -124,11 +124,11 @@ int pselect(int nfds, fd_set *readfds, fd_set *writefds, fd_set *exceptfds,
   END_CANCELATION_POINT;
 
   STRACE("pselect(%d, %s → [%s], %s → [%s], %s → [%s], %s, %s) → %d% m", nfds,
-         DescribeFdSet(rc, nfds, old_readfds_ptr),
+         DescribeFdSet(0, nfds, old_readfds_ptr),
          DescribeFdSet(rc, nfds, readfds),
-         DescribeFdSet(rc, nfds, old_writefds_ptr),
+         DescribeFdSet(0, nfds, old_writefds_ptr),
          DescribeFdSet(rc, nfds, writefds),
-         DescribeFdSet(rc, nfds, old_exceptfds_ptr),
+         DescribeFdSet(0, nfds, old_exceptfds_ptr),
          DescribeFdSet(rc, nfds, exceptfds),  //
          DescribeTimespec(0, timeout),        //
          DescribeSigset(0, sigmask), rc);

libc/intrin/describefdset.c

@@ -31,6 +31,8 @@ const char *_DescribeFdSet(char buf[N], ssize_t rc, int nfds, fd_set *fds) {
 
   if (!fds)
     return "NULL";
+  if (rc == -1)
+    return "n/a";
   if (kisdangerous(fds)) {
     ksnprintf(buf, N, "%p", fds);
     return buf;

libc/proc/proc.c

@@ -102,14 +102,14 @@ textwindows int __proc_harvest(struct Proc *pr, bool iswait4) {
     pr->handle = status & 0x00FFFFFF;
   } else {
     // handle child _Exit()
-    if (status == 0xc9af3d51u) {
+    if (status == 0xc9af3d51u)
       status = kNtStillActive;
-    }
     pr->wstatus = status;
     if (!iswait4 && !pr->waiters && !__proc.waiters &&
         (__sighandrvas[SIGCHLD] == (uintptr_t)SIG_IGN ||
          (__sighandflags[SIGCHLD] & SA_NOCLDWAIT))) {
       // perform automatic zombie reaping
+      STRACE("automatically reaping zombie");
       dll_remove(&__proc.list, &pr->elem);
       dll_make_first(&__proc.free, &pr->elem);
       CloseHandle(pr->handle);
@@ -192,9 +192,8 @@ static textwindows dontinstrument uint32_t __proc_worker(void *arg) {
         continue;
       if (j == i)
         continue;
-      if (!--objects[j]->waiters && objects[j]->status == PROC_UNDEAD) {
+      if (!--objects[j]->waiters && objects[j]->status == PROC_UNDEAD)
         __proc_free(objects[j]);
-      }
     }
 
     // check if we need to churn due to >64 processes
@@ -219,9 +218,8 @@ static textwindows dontinstrument uint32_t __proc_worker(void *arg) {
       case PROC_ZOMBIE:
         break;
       case PROC_UNDEAD:
-        if (!objects[i]->waiters) {
+        if (!objects[i]->waiters)
           __proc_free(objects[i]);
-        }
         break;
       default:
         __builtin_unreachable();
@@ -233,9 +231,8 @@ static textwindows dontinstrument uint32_t __proc_worker(void *arg) {
     // 1. wait4() is being used
     // 2. SIGCHLD has SIG_IGN handler
     // 3. SIGCHLD has SA_NOCLDWAIT flag
-    if (sic) {
+    if (sic)
       __sig_generate(SIGCHLD, sic);
-    }
   }
   return 0;
 }