diff options
Diffstat (limited to 'winsup/cygwin/select.cc')
| -rw-r--r-- | winsup/cygwin/select.cc | 26 |
1 files changed, 12 insertions, 14 deletions
diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc index 5c26248ab..d11a1158e 100644 --- a/winsup/cygwin/select.cc +++ b/winsup/cygwin/select.cc @@ -16,6 +16,7 @@ details. */ #include "winsup.h" #include <stdlib.h> +#include "ntdll.h" #include <wingdi.h> #include <winuser.h> @@ -294,7 +295,7 @@ select_stuff::wait (fd_set *readfds, fd_set *writefds, fd_set *exceptfds, select_printf ("woke up. wait_ret %d. verifying", wait_ret); s = &start; bool gotone = false; - /* Some types of object (e.g., consoles) wake up on "inappropriate" events + /* Some types of objects (e.g., consoles) wake up on "inappropriate" events like mouse movements. The verify function will detect these situations. If it returns false, then this wakeup was a false alarm and we should go back to waiting. */ @@ -505,10 +506,6 @@ out: fh->get_name ()); else { -#if 0 -/* FIXME: This code is not quite correct. There's no better solution - so far but to always treat the write side of the pipe as writable. */ - IO_STATUS_BLOCK iosb = {0}; FILE_PIPE_LOCAL_INFORMATION fpli = {0}; @@ -519,19 +516,18 @@ out: FilePipeLocalInformation)) { /* If NtQueryInformationFile fails, optimistically assume the - pipe is writable. This could happen on Win9x, because - NtQueryInformationFile is not available, or if we somehow + pipe is writable. This could happen if we somehow inherit a pipe that doesn't permit FILE_READ_ATTRIBUTES access on the write end. */ select_printf ("%s, NtQueryInformationFile failed", fh->get_name ()); gotone += s->write_ready = true; } - /* Ensure that enough space is available for atomic writes, - as required by POSIX. Subsequent writes with size > PIPE_BUF - can still block, but most (all?) UNIX variants seem to work - this way (e.g., BSD, Linux, Solaris). */ - else if (fpli.WriteQuotaAvailable >= PIPE_BUF) + /* If there is anything available in the pipe buffer then signal + that. This means that a pipe could still block since you could + be trying to write more to the pipe than is available in the + buffer but that is the hazard of select(). */ + else if (fpli.WriteQuotaAvailable) { select_printf ("%s, ready for write: size %lu, avail %lu", fh->get_name (), @@ -539,6 +535,10 @@ out: fpli.WriteQuotaAvailable); gotone += s->write_ready = true; } +#if 0 +/* FIXME: This code is not quite correct. There's no better solution + so far but to make simple assumptions based on WriteQuotaAvailable. */ + /* If we somehow inherit a tiny pipe (size < PIPE_BUF), then consider the pipe writable only if it is completely empty, to minimize the probability that a subsequent write will block. */ @@ -551,8 +551,6 @@ out: fpli.WriteQuotaAvailable); gotone += s->write_ready = true; } -#else - gotone += s->write_ready = true; #endif } } |