The queue is cleaned up by removing the entries having si_signo == 0 while processing the queued signals, however, sipacket::process() may set si_signo in the queue to 0 of the entry already processed but not succeed by calling sig_clear(). This patch ensures the sig_clear() to remove the entry from the queue chain.
Addresses: https://cygwin.com/pipermail/cygwin/2024-November/256744.html Fixes: 9d2155089e87 ("(wait_sig): Define variable q to be the start of the signal queue. Just iterate through sigq queue, deleting processed or zeroed signals") Reported-by: Christian Franke <christian.fra...@t-online.de> Reviewed-by: Corinna Vinschen <cori...@vinschen.de> Signed-off-by: Takashi Yano <takashi.y...@nifty.ne.jp> --- winsup/cygwin/local_includes/sigproc.h | 3 +- winsup/cygwin/sigproc.cc | 48 +++++++++++++++++--------- 2 files changed, 34 insertions(+), 17 deletions(-) diff --git a/winsup/cygwin/local_includes/sigproc.h b/winsup/cygwin/local_includes/sigproc.h index 46e26db19..8b7062aae 100644 --- a/winsup/cygwin/local_includes/sigproc.h +++ b/winsup/cygwin/local_includes/sigproc.h @@ -50,8 +50,9 @@ struct sigpacket { HANDLE wakeup; HANDLE thread_handle; - struct sigpacket *next; }; + struct sigpacket *next; + struct sigpacket *prev; int process (); int setup_handler (void *, struct sigaction&, _cygtls *); }; diff --git a/winsup/cygwin/sigproc.cc b/winsup/cygwin/sigproc.cc index 4d50a5865..8ffb90a2c 100644 --- a/winsup/cygwin/sigproc.cc +++ b/winsup/cygwin/sigproc.cc @@ -111,7 +111,7 @@ class pending_signals public: void add (sigpacket&); bool pending () {retry = !!start.next; return retry;} - void clear (int sig) {sigs[sig].si.si_signo = 0;} + void clear (int sig); void clear (_cygtls *tls); friend void sig_dispatch_pending (bool); friend void wait_sig (VOID *arg); @@ -432,21 +432,35 @@ sig_clear (int sig) sigq.clear (sig); } +/* Clear pending signals of specific si_signo. + Called from sigpacket::process(). */ +void +pending_signals::clear (int sig) +{ + sigpacket *q = sigs + sig; + if (!sig || !q->si.si_signo) + return; + q->si.si_signo = 0; + q->prev->next = q->next; + if (q->next) + q->next->prev = q->prev; +} + /* Clear pending signals of specific thread. Called under TLS lock from _cygtls::remove_pending_sigs. */ void pending_signals::clear (_cygtls *tls) { - sigpacket *q = &start, *qnext; + sigpacket *q = &start; - while ((qnext = q->next)) - if (qnext->sigtls == tls) + while ((q = q->next)) + if (q->sigtls == tls) { - qnext->si.si_signo = 0; - q->next = qnext->next; + q->si.si_signo = 0; + q->prev->next = q->next; + if (q->next) + q->next->prev = q->prev; } - else - q = qnext; } /* Clear pending signals of specific thread. Called from _cygtls::remove */ @@ -1299,7 +1313,10 @@ pending_signals::add (sigpacket& pack) return; *se = pack; se->next = start.next; - start.next = se; + se->prev = &start; + se->prev->next = se; + if (se->next) + se->next->prev = se; } /* Process signals by waiting for signal data to arrive in a pipe. @@ -1450,17 +1467,16 @@ wait_sig (VOID *) case __SIGFLUSHFAST: if (!sig_held) { - sigpacket *qnext; /* Check the queue for signals. There will always be at least one thing on the queue if this was a valid signal. */ - while ((qnext = q->next)) + while ((q = q->next)) { - if (qnext->si.si_signo && qnext->process () <= 0) - q = qnext; - else + if (q->si.si_signo && q->process () > 0) { - q->next = qnext->next; - qnext->si.si_signo = 0; + q->si.si_signo = 0; + q->prev->next = q->next; + if (q->next) + q->next->prev = q->prev; } } /* At least one signal still queued? The event is used in select -- 2.45.1
