1.0.25.46: restore errno in signal handlers

[sbcl.git] / doc / internals / signals.texinfo

diff --git a/doc/internals/signals.texinfo b/doc/internals/signals.texinfo
index dc2b3a6..acd47b7 100644 (file)
--- a/doc/internals/signals.texinfo
+++ b/doc/internals/signals.texinfo
@@ -73,24 +73,10 @@ is deferred by pseudo atomic and @code{WITHOUT-GCING}.
 @node Implementation warts
 @section Implementation warts
 
-@subsection RT signals
-
-Sending and receiving the same number of signals is crucial for
-@code{INTERRUPT-THREAD} and @code{sig_stop_for_gc}, hence they are
-real-time signals for which the kernel maintains a queue as opposed to
-just setting a flag for ``sigint pending''.
-
-Note, however, that the rt signal queue is finite and on current linux
-kernels a system wide resource. If the queue is full, SBCL tries to
-signal until it succeeds. This behaviour can lead to deadlocks, if a
-thread in a @code{WITHOUT-INTERRUPTS} is interrupted many times,
-filling up the queue and then a gc hits and tries to send
-@code{SIG_STOP_FOR_GC}.
-
 @subsection Miscellaneous issues
 
-Signal handlers should automatically restore errno and fp
-state. Currently, this is not the case.
+Signal handlers automatically restore errno and fp state, but
+arrange_return_to_lisp_function does not restore errno.
 
 @subsection POSIX -- Letter and Spirit
 
@@ -159,6 +145,10 @@ derive the rule: in a @code{WITHOUT-GCING} form (or pseudo atomic for
 that matter) never wait for another thread that's not in
 @code{WITHOUT-GCING}.
 
+Somewhat of a special case, it is enforced by the runtime that
+@code{SIG_STOP_FOR_GC} and @code{SIG_RESUME_FROM_GC} always unblocked
+when we might trigger a gc (i.e. on alloc or calling into Lisp).
+
 @subsection Calling user code
 
 For the reasons above, calling user code, i.e. functions passed in, or