From 0169458101d1c9e915f842a765a9afe4ee69867e Mon Sep 17 00:00:00 2001 From: Corinna Vinschen Date: Fri, 16 Aug 2019 16:36:06 +0200 Subject: [PATCH 1/2] Cygwin: select: revamp non-polling code for signalfd Rather than waiting for signalfd_select_wait in a thread, which is racy, create a global event "my_pendingsigs_evt" which is set and reset by wait_sig depending on the fact if signals are pending because they are blocked and no thread cares. This in turn allows to WFMO on this event in select as soon as signalfds are present in the read descriptor set, and the peek and verify functionality will then check if one of the present signalfds is affected. Signed-off-by: Corinna Vinschen --- winsup/cygwin/cygtls.h | 2 +- winsup/cygwin/exceptions.cc | 8 ---- winsup/cygwin/select.cc | 80 ++---------------------------------- winsup/cygwin/select.h | 11 +---- winsup/cygwin/signal.cc | 1 - winsup/cygwin/sigproc.cc | 17 ++++++++ winsup/cygwin/tlsoffsets.h | 16 ++++---- winsup/cygwin/tlsoffsets64.h | 16 ++++---- 8 files changed, 40 insertions(+), 111 deletions(-) diff --git a/winsup/cygwin/cygtls.h b/winsup/cygwin/cygtls.h index 65a905c32078..a2e3676fc722 100644 --- a/winsup/cygwin/cygtls.h +++ b/winsup/cygwin/cygtls.h @@ -189,8 +189,8 @@ public: stack_t altstack; siginfo_t *sigwait_info; HANDLE signal_arrived; - HANDLE signalfd_select_wait; bool will_wait_for_signal; + long __align; /* Needed to align context to 16 byte. */ /* context MUST be aligned to 16 byte, otherwise RtlCaptureContext fails. If you prepend cygtls members here, make sure context stays 16 byte aligned. */ diff --git a/winsup/cygwin/exceptions.cc b/winsup/cygwin/exceptions.cc index 9bdf9f054c0a..f35411e3bb0e 100644 --- a/winsup/cygwin/exceptions.cc +++ b/winsup/cygwin/exceptions.cc @@ -1469,14 +1469,6 @@ sigpacket::process () if (issig_wait) { tls->sigwait_mask = 0; - /* If the catching thread is running select on a signalfd, don't call - the signal handler and don't remove the signal from the queue. */ - if (tls->signalfd_select_wait) - { - SetEvent (tls->signalfd_select_wait); - rc = 0; - goto done; - } goto dosig; } diff --git a/winsup/cygwin/select.cc b/winsup/cygwin/select.cc index 688859b50290..d29f3d2f4ffa 100644 --- a/winsup/cygwin/select.cc +++ b/winsup/cygwin/select.cc @@ -1867,80 +1867,6 @@ fhandler_windows::select_except (select_stuff *ss) return s; } -static int start_thread_signalfd (select_record *, select_stuff *); - -static DWORD WINAPI -thread_signalfd (void *arg) -{ - select_signalfd_info *si = (select_signalfd_info *) arg; - bool event = false; - - while (!event) - { - sigset_t set = 0; - _cygtls *tls = si->start->tls; - - for (select_record *s = si->start; (s = s->next); ) - if (s->startup == start_thread_signalfd) - set |= ((fhandler_signalfd *) s->fh)->get_sigset (); - set_signal_mask (tls->sigwait_mask, set); - tls->signalfd_select_wait = si->evt; - sig_dispatch_pending (true); - switch (WaitForSingleObject (si->evt, INFINITE)) - { - case WAIT_OBJECT_0: - tls->signalfd_select_wait = NULL; - event = true; - break; - default: - break; - } - if (si->stop_thread) - break; - if (!event) - Sleep (1L); - } - CloseHandle (si->evt); - return 0; -} - -static int -start_thread_signalfd (select_record *me, select_stuff *stuff) -{ - select_signalfd_info *si; - - if ((si = stuff->device_specific_signalfd)) - { - me->h = *si->thread; - return 1; - } - si = new select_signalfd_info; - si->start = &stuff->start; - si->stop_thread = false; - si->evt = CreateEventW (&sec_none_nih, TRUE, FALSE, NULL); - si->thread = new cygthread (thread_signalfd, si, "signalfdsel"); - me->h = *si->thread; - stuff->device_specific_signalfd = si; - return 1; -} - -static void -signalfd_cleanup (select_record *, select_stuff *stuff) -{ - select_signalfd_info *si; - - if (!(si = stuff->device_specific_signalfd)) - return; - if (si->thread) - { - si->stop_thread = true; - SetEvent (si->evt); - si->thread->detach (); - } - delete si; - stuff->device_specific_signalfd = NULL; -} - static int peek_signalfd (select_record *me, bool) { @@ -1960,17 +1886,19 @@ verify_signalfd (select_record *me, fd_set *rfds, fd_set *wfds, fd_set *efds) return peek_signalfd (me, true); } +extern HANDLE my_pendingsigs_evt; + select_record * fhandler_signalfd::select_read (select_stuff *stuff) { select_record *s = stuff->start.next; if (!s->startup) { - s->startup = start_thread_signalfd; + s->startup = no_startup; s->verify = verify_signalfd; - s->cleanup = signalfd_cleanup; } s->peek = peek_signalfd; + s->h = my_pendingsigs_evt; /* wait_sig sets this if signal are pending */ s->read_selected = true; s->read_ready = false; return s; diff --git a/winsup/cygwin/select.h b/winsup/cygwin/select.h index 19f9d7dc2434..7d6dee753dba 100644 --- a/winsup/cygwin/select.h +++ b/winsup/cygwin/select.h @@ -71,12 +71,6 @@ struct select_serial_info: public select_info select_serial_info (): select_info () {} }; -struct select_signalfd_info: public select_info -{ - HANDLE evt; - select_signalfd_info (): select_info () {} -}; - class select_stuff { public: @@ -97,7 +91,6 @@ public: select_fifo_info *device_specific_fifo; select_socket_info *device_specific_socket; select_serial_info *device_specific_serial; - select_signalfd_info *device_specific_signalfd; bool test_and_set (int, fd_set *, fd_set *, fd_set *); int poll (fd_set *, fd_set *, fd_set *); @@ -110,8 +103,8 @@ public: device_specific_pipe (NULL), device_specific_fifo (NULL), device_specific_socket (NULL), - device_specific_serial (NULL), - device_specific_signalfd (NULL) {} + device_specific_serial (NULL) + {} }; extern "C" int cygwin_select (int , fd_set *, fd_set *, fd_set *, diff --git a/winsup/cygwin/signal.cc b/winsup/cygwin/signal.cc index 920a533f3a2b..8ac59d4b9366 100644 --- a/winsup/cygwin/signal.cc +++ b/winsup/cygwin/signal.cc @@ -606,7 +606,6 @@ sigwait_common (const sigset_t *set, siginfo_t *info, PLARGE_INTEGER waittime) __try { set_signal_mask (_my_tls.sigwait_mask, *set); - _my_tls.signalfd_select_wait = NULL; sig_dispatch_pending (true); switch (cygwait (NULL, waittime, diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc index 8003e2db6259..91abb717c25b 100644 --- a/winsup/cygwin/sigproc.cc +++ b/winsup/cygwin/sigproc.cc @@ -57,6 +57,9 @@ _cygtls NO_COPY *_sig_tls; Static HANDLE my_sendsig; Static HANDLE my_readsig; +/* Used in select if a signalfd is part of the read descriptor set */ +HANDLE NO_COPY my_pendingsigs_evt; + /* Function declarations */ static int __reg1 checkstate (waitq *); static __inline__ bool get_proc_lock (DWORD, DWORD); @@ -455,6 +458,10 @@ sigproc_init () } ProtectHandle (my_readsig); myself->sendsig = my_sendsig; + my_pendingsigs_evt = CreateEvent (NULL, TRUE, FALSE, NULL); + if (!my_pendingsigs_evt) + api_fatal ("couldn't create pending signal event, %E"); + /* sync_proc_subproc is used by proc_subproc. It serializes access to the children and proc arrays. */ sync_proc_subproc.init ("sync_proc_subproc"); @@ -1398,6 +1405,16 @@ wait_sig (VOID *) qnext->si.si_signo = 0; } } + /* At least one signal still queued? The event is used in select + only, and only to decide if WFMO should wake up in case a + signalfd is waiting via select/poll for being ready to read a + pending signal. This method wakes up all threads hanging in + select and having a signalfd, as soon as a pending signal is + available, but it's certainly better than constant polling. */ + if (sigq.start.next) + SetEvent (my_pendingsigs_evt); + else + ResetEvent (my_pendingsigs_evt); if (pack.si.si_signo == SIGCHLD) clearwait = true; } diff --git a/winsup/cygwin/tlsoffsets.h b/winsup/cygwin/tlsoffsets.h index 8003a1fffdec..13d1003e334f 100644 --- a/winsup/cygwin/tlsoffsets.h +++ b/winsup/cygwin/tlsoffsets.h @@ -29,10 +29,10 @@ //; $tls::psigwait_info = 2852; //; $tls::signal_arrived = -9844; //; $tls::psignal_arrived = 2856; -//; $tls::signalfd_select_wait = -9840; -//; $tls::psignalfd_select_wait = 2860; -//; $tls::will_wait_for_signal = -9836; -//; $tls::pwill_wait_for_signal = 2864; +//; $tls::will_wait_for_signal = -9840; +//; $tls::pwill_wait_for_signal = 2860; +//; $tls::__align = -9836; +//; $tls::p__align = 2864; //; $tls::context = -9832; //; $tls::pcontext = 2868; //; $tls::thread_id = -9084; @@ -91,10 +91,10 @@ #define tls_psigwait_info (2852) #define tls_signal_arrived (-9844) #define tls_psignal_arrived (2856) -#define tls_signalfd_select_wait (-9840) -#define tls_psignalfd_select_wait (2860) -#define tls_will_wait_for_signal (-9836) -#define tls_pwill_wait_for_signal (2864) +#define tls_will_wait_for_signal (-9840) +#define tls_pwill_wait_for_signal (2860) +#define tls___align (-9836) +#define tls_p__align (2864) #define tls_context (-9832) #define tls_pcontext (2868) #define tls_thread_id (-9084) diff --git a/winsup/cygwin/tlsoffsets64.h b/winsup/cygwin/tlsoffsets64.h index 2e9d590c31df..d137408d0e0c 100644 --- a/winsup/cygwin/tlsoffsets64.h +++ b/winsup/cygwin/tlsoffsets64.h @@ -29,10 +29,10 @@ //; $tls::psigwait_info = 4144; //; $tls::signal_arrived = -8648; //; $tls::psignal_arrived = 4152; -//; $tls::signalfd_select_wait = -8640; -//; $tls::psignalfd_select_wait = 4160; -//; $tls::will_wait_for_signal = -8632; -//; $tls::pwill_wait_for_signal = 4168; +//; $tls::will_wait_for_signal = -8640; +//; $tls::pwill_wait_for_signal = 4160; +//; $tls::__align = -8632; +//; $tls::p__align = 4168; //; $tls::context = -8624; //; $tls::pcontext = 4176; //; $tls::thread_id = -7328; @@ -91,10 +91,10 @@ #define tls_psigwait_info (4144) #define tls_signal_arrived (-8648) #define tls_psignal_arrived (4152) -#define tls_signalfd_select_wait (-8640) -#define tls_psignalfd_select_wait (4160) -#define tls_will_wait_for_signal (-8632) -#define tls_pwill_wait_for_signal (4168) +#define tls_will_wait_for_signal (-8640) +#define tls_pwill_wait_for_signal (4160) +#define tls___align (-8632) +#define tls_p__align (4168) #define tls_context (-8624) #define tls_pcontext (4176) #define tls_thread_id (-7328) -- 2.20.1