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From: Corinna Vinschen <corinna@sourceware.org> To: cygwin-cvs@sourceware.org Subject: [newlib-cygwin] Cygwin: pipe, fifo: Release select_sem semaphore as much as needed. Date: Tue, 14 Sep 2021 15:08:15 +0000 (GMT) [thread overview] Message-ID: <20210914150815.1E08B385782F@sourceware.org> (raw) https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=e4e45379796f999a07029df3bd15918105a751e3 commit e4e45379796f999a07029df3bd15918105a751e3 Author: Takashi Yano <takashi.yano@nifty.ne.jp> Date: Tue Sep 14 18:50:49 2021 +0900 Cygwin: pipe, fifo: Release select_sem semaphore as much as needed. - Currently, raw_read(), raw_write() and close() release select_sem unconditionally even if no waiter for select_sem exists. With this patch, only the minimum number of semaphores required is released. Diff: --- winsup/cygwin/fhandler.h | 4 ++++ winsup/cygwin/fhandler_fifo.cc | 28 ++++++++++++++++++++++------ winsup/cygwin/fhandler_pipe.cc | 28 +++++++++++++++++++++------- 3 files changed, 47 insertions(+), 13 deletions(-) diff --git a/winsup/cygwin/fhandler.h b/winsup/cygwin/fhandler.h index db2325144..9580a698c 100644 --- a/winsup/cygwin/fhandler.h +++ b/winsup/cygwin/fhandler.h @@ -1177,6 +1177,7 @@ class fhandler_pipe_fifo: public fhandler_base protected: size_t pipe_buf_size; HANDLE query_hdl; + virtual void release_select_sem (const char *) {}; public: fhandler_pipe_fifo (); @@ -1201,6 +1202,7 @@ class fhandler_pipe: public fhandler_pipe_fifo private: HANDLE read_mtx; pid_t popen_pid; + void release_select_sem (const char *); public: fhandler_pipe (); @@ -1444,6 +1446,8 @@ class fhandler_fifo: public fhandler_pipe_fifo void shared_fc_handler_updated (bool val) { shmem->shared_fc_handler_updated (val); } + void release_select_sem (const char *); + public: fhandler_fifo (); ~fhandler_fifo () diff --git a/winsup/cygwin/fhandler_fifo.cc b/winsup/cygwin/fhandler_fifo.cc index 37498f547..489ba528c 100644 --- a/winsup/cygwin/fhandler_fifo.cc +++ b/winsup/cygwin/fhandler_fifo.cc @@ -1185,6 +1185,22 @@ fhandler_fifo::take_ownership (DWORD timeout) return ret; } +void +fhandler_fifo::release_select_sem (const char *from) +{ + LONG n_release; + if (reader) /* Number of select() call. */ + n_release = get_obj_handle_count (select_sem) + - get_obj_handle_count (read_ready); + else /* Number of select() and reader */ + n_release = get_obj_handle_count (select_sem) + - get_obj_handle_count (get_handle ()); + debug_printf("%s(%s) release %d", from, + reader ? "reader" : "writer", n_release); + if (n_release) + ReleaseSemaphore (select_sem, n_release, NULL); +} + void __reg3 fhandler_fifo::raw_read (void *in_ptr, size_t& len) { @@ -1372,7 +1388,7 @@ out: fifo_client_unlock (); reading_unlock (); if (select_sem) - ReleaseSemaphore (select_sem, get_obj_handle_count (select_sem), NULL); + release_select_sem ("raw_read"); } int __reg2 @@ -1483,6 +1499,11 @@ fhandler_fifo::cancel_reader_thread () int fhandler_fifo::close () { + if (select_sem) + { + release_select_sem ("close"); + NtClose (select_sem); + } if (writer) { nwriters_lock (); @@ -1574,11 +1595,6 @@ fhandler_fifo::close () NtClose (write_ready); if (writer_opening) NtClose (writer_opening); - if (select_sem) - { - ReleaseSemaphore (select_sem, get_obj_handle_count (select_sem), NULL); - NtClose (select_sem); - } if (nohandle ()) return 0; else diff --git a/winsup/cygwin/fhandler_pipe.cc b/winsup/cygwin/fhandler_pipe.cc index b7d4cb5cc..7e5ab328c 100644 --- a/winsup/cygwin/fhandler_pipe.cc +++ b/winsup/cygwin/fhandler_pipe.cc @@ -233,6 +233,22 @@ fhandler_pipe::get_proc_fd_name (char *buf) return buf; } +void +fhandler_pipe::release_select_sem (const char *from) +{ + LONG n_release; + if (get_dev () == FH_PIPER) /* Number of select() and writer */ + n_release = get_obj_handle_count (select_sem) + - get_obj_handle_count (read_mtx); + else /* Number of select() call */ + n_release = get_obj_handle_count (select_sem) + - get_obj_handle_count (query_hdl); + debug_printf("%s(%s) release %d", from, + get_dev () == FH_PIPER ? "PIPER" : "PIPEW", n_release); + if (n_release) + ReleaseSemaphore (select_sem, n_release, NULL); +} + void __reg3 fhandler_pipe::raw_read (void *ptr, size_t& len) { @@ -324,8 +340,7 @@ fhandler_pipe::raw_read (void *ptr, size_t& len) ptr = ((char *) ptr) + nbytes_now; nbytes += nbytes_now; if (select_sem && nbytes_now > 0) - ReleaseSemaphore (select_sem, - get_obj_handle_count (select_sem), NULL); + release_select_sem ("raw_read"); } else { @@ -496,8 +511,7 @@ fhandler_pipe_fifo::raw_write (const void *ptr, size_t len) ptr = ((char *) ptr) + nbytes_now; nbytes += nbytes_now; if (select_sem && nbytes_now > 0) - ReleaseSemaphore (select_sem, - get_obj_handle_count (select_sem), NULL); + release_select_sem ("raw_write"); /* 0 bytes returned? EAGAIN. See above. */ if (NT_SUCCESS (status) && nbytes == 0) set_errno (EAGAIN); @@ -591,13 +605,13 @@ fhandler_pipe::dup (fhandler_base *child, int flags) int fhandler_pipe::close () { - if (read_mtx) - CloseHandle (read_mtx); if (select_sem) { - ReleaseSemaphore (select_sem, get_obj_handle_count (select_sem), NULL); + release_select_sem ("close"); CloseHandle (select_sem); } + if (read_mtx) + CloseHandle (read_mtx); if (query_hdl) CloseHandle (query_hdl); return fhandler_base::close ();
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