From d1c2e0baeba415190676f5ed6d1b75bc242a6166 Mon Sep 17 00:00:00 2001
From: Jason Volk <jason@zemos.net>
Date: Thu, 8 Oct 2020 17:54:01 -0700
Subject: [PATCH] ircd::ctx: Belay marking entry point until after initial
 interrupt check.

---
 ircd/ctx.cc | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/ircd/ctx.cc b/ircd/ctx.cc
index 1a9341475..c928b52d7 100644
--- a/ircd/ctx.cc
+++ b/ircd/ctx.cc
@@ -150,10 +150,8 @@ noexcept try
 	this->yc = &yc;
 	notes = 1;
 	stack.base = uintptr_t(__builtin_frame_address(0));
-	mark(prof::event::ENTER);
 	const unwind atexit{[this]
 	{
-		mark(prof::event::LEAVE);
 		adjoindre.notify_all();
 		stack.at = 0;
 		notes = 0;
@@ -166,6 +164,17 @@ noexcept try
 	// Check for a precocious interrupt
 	interruption_point();
 
+	// Mark the point of context entry only after the interrupt check. If the
+	// context was interrupted without ever entering (which makes the above
+	// check throw) we never record any execution slice or increment the epoch
+	// counter for it. This can allow a parent context to assume application
+	// state remains unmodified by the aborted context.
+	mark(prof::event::ENTER);
+	const unwind leaver{[this]
+	{
+		mark(prof::event::LEAVE);
+	}};
+
 	// Call the user's function.
 	func();