From: Matthew Dillon <dillon@apollo.backplane.com>
Date: Fri, 29 Jul 2011 08:19:29 +0000 (-0700)
Subject: kernel - Fix signal delivery races
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/025d695a653d667f8d06e460e9e0e625ded69efb

kernel - Fix signal delivery races

* The send side was using p->p_token but the processing code from trap
  was still using the mp_lock.  Fix the trap processing code to use
  p->p_token.

* This fixes several nasty races that can cause signals to be lost and
  vkernels to freeze, and possibly other programs which depend on signals
  between threads.
---

diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
index d82b1a9a49..e5651b84e6 100644
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -1916,6 +1916,8 @@ issignal(struct lwp *lp, int maytrace)
 /*
  * Take the action for the specified signal
  * from the current set of pending signals.
+ *
+ * Caller must hold p->p_token
  */
 void
 postsig(int sig)
diff --git a/sys/platform/pc32/i386/trap.c b/sys/platform/pc32/i386/trap.c
index 96b8af2bd0..0432e5495b 100644
--- a/sys/platform/pc32/i386/trap.c
+++ b/sys/platform/pc32/i386/trap.c
@@ -273,10 +273,10 @@ recheck:
 	 * to restore the virtual kernel's vmspace before posting the upcall.
 	 */
 	if (p->p_flag & P_UPCALLPEND) {
+		lwkt_gettoken(&p->p_token);
 		p->p_flag &= ~P_UPCALLPEND;
-		get_mplock();
 		postupcall(lp);
-		rel_mplock();
+		lwkt_reltoken(&p->p_token);
 		goto recheck;
 	}
 
@@ -287,9 +287,9 @@ recheck:
 	 * WARNING!  postsig() can exit and not return.
 	 */
 	if ((sig = CURSIG_TRACE(lp)) != 0) {
-		get_mplock();
+		lwkt_gettoken(&p->p_token);
 		postsig(sig);
-		rel_mplock();
+		lwkt_reltoken(&p->p_token);
 		goto recheck;
 	}
 
diff --git a/sys/platform/pc64/x86_64/trap.c b/sys/platform/pc64/x86_64/trap.c
index d22e5d40ce..e507758db0 100644
--- a/sys/platform/pc64/x86_64/trap.c
+++ b/sys/platform/pc64/x86_64/trap.c
@@ -237,10 +237,10 @@ recheck:
 	 * to restore the virtual kernel's vmspace before posting the upcall.
 	 */
 	if (p->p_flag & P_UPCALLPEND) {
+		lwkt_gettoken(&p->p_token);
 		p->p_flag &= ~P_UPCALLPEND;
-		get_mplock();
 		postupcall(lp);
-		rel_mplock();
+		lwkt_reltoken(&p->p_token);
 		goto recheck;
 	}
 
@@ -251,9 +251,9 @@ recheck:
 	 * WARNING!  postsig() can exit and not return.
 	 */
 	if ((sig = CURSIG_TRACE(lp)) != 0) {
-		get_mplock();
+		lwkt_gettoken(&p->p_token);
 		postsig(sig);
-		rel_mplock();
+		lwkt_reltoken(&p->p_token);
 		goto recheck;
 	}
 
diff --git a/sys/platform/vkernel/i386/trap.c b/sys/platform/vkernel/i386/trap.c
index ff69ae1d73..fc025de5ed 100644
--- a/sys/platform/vkernel/i386/trap.c
+++ b/sys/platform/vkernel/i386/trap.c
@@ -247,10 +247,10 @@ recheck:
 	 * Post any pending upcalls
 	 */
 	if (p->p_flag & P_UPCALLPEND) {
-		get_mplock();
+		lwkt_gettoken(&p->p_token);
 		p->p_flag &= ~P_UPCALLPEND;
 		postupcall(lp);
-		rel_mplock();
+		lwkt_reltoken(&p->p_token);
 		goto recheck;
 	}
 
@@ -260,9 +260,9 @@ recheck:
 	 * WARNING!  postsig() can exit and not return.
 	 */
 	if ((sig = CURSIG_TRACE(lp)) != 0) {
-		get_mplock();
+		lwkt_gettoken(&p->p_token);
 		postsig(sig);
-		rel_mplock();
+		lwkt_reltoken(&p->p_token);
 		goto recheck;
 	}
 
diff --git a/sys/platform/vkernel64/x86_64/trap.c b/sys/platform/vkernel64/x86_64/trap.c
index 874dfc553a..02227ba66c 100644
--- a/sys/platform/vkernel64/x86_64/trap.c
+++ b/sys/platform/vkernel64/x86_64/trap.c
@@ -247,10 +247,10 @@ recheck:
 	 * Post any pending upcalls
 	 */
 	if (p->p_flag & P_UPCALLPEND) {
-		get_mplock();
+		lwkt_gettoken(&p->p_token);
 		p->p_flag &= ~P_UPCALLPEND;
 		postupcall(lp);
-		rel_mplock();
+		lwkt_reltoken(&p->p_token);
 		goto recheck;
 	}
 
@@ -260,9 +260,9 @@ recheck:
 	 * WARNING!  postsig() can exit and not return.
 	 */
 	if ((sig = CURSIG_TRACE(lp)) != 0) {
-		get_mplock();
+		lwkt_gettoken(&p->p_token);
 		postsig(sig);
-		rel_mplock();
+		lwkt_reltoken(&p->p_token);
 		goto recheck;
 	}