Commit Diff

Commit:
7bf2db4c2ae30c0f7b320e57060715bf6279e98a
From:
Dan Cross <cross@gajendra.net>
Date:
Message:
malloc: remove locking The issue manifests in fork: POSIX fork mandates that a fork'd process is created with a single thread. If a multithreaded program forks, and some thread was in malloc() when the fork() happened, then in the child the lock will be held but there will be no thread to release it. We assume the system malloc() must already know how to deal with this and is thread-safe, but it won't know about our custom spinlock. Judging that this is no longer necessary (the lock code was added 15 years ago) we remove it. Signed-off-by: Dan Cross <cross@gajendra.net>
Actions:
Patch | Tree
commit - 3ef80ba5f5c29a8367d32353a9620ec4cf9cb880
commit + 7bf2db4c2ae30c0f7b320e57060715bf6279e98a
blob - 9132235b3419d7be512670cb6002f865119f72e7
blob + 7b590bc4b5971d478a57b5b8598659cf147b0d22
--- src/cmd/9term/malloc.c
+++ src/cmd/9term/malloc.c
@@ -7,8 +7,6 @@
 #define NOPLAN9DEFINES
 #include <libc.h>
 
-static Lock malloclock;
-
 void*
 p9malloc(ulong n)
 {
@@ -16,9 +14,7 @@ p9malloc(ulong n)
 
 	if(n == 0)
 		n++;
-	lock(&malloclock);
 	v = malloc(n);
-	unlock(&malloclock);
 	print("p9malloc %lud => %p; pc %lux\n", n, v, getcallerpc(&n));
 	return v;
 }
@@ -28,10 +24,8 @@ p9free(void *v)
 {
 	if(v == nil)
 		return;
-	lock(&malloclock);
 	print("p9free %p; pc %lux\n", v, getcallerpc(&v));
 	free(v);
-	unlock(&malloclock);
 }
 
 void*
@@ -42,9 +36,7 @@ p9calloc(ulong a, ulong b)
 	if(a*b == 0)
 		a = b = 1;
 
-	lock(&malloclock);
 	v = calloc(a*b, 1);
-	unlock(&malloclock);
 	print("p9calloc %lud %lud => %p; pc %lux\n", a, b, v, getcallerpc(&a));
 	return v;
 }
@@ -54,9 +46,7 @@ p9realloc(void *v, ulong n)
 {
 	void *vv;
 
-	lock(&malloclock);
 	vv = realloc(v, n);
-	unlock(&malloclock);
 	print("p9realloc %p %lud => %p; pc %lux\n", v, n, vv, getcallerpc(&v));
 	return vv;
 }
blob - 51a2c61f52ecf52d32fcd4e61e08862d481f774e
blob + 744af835ee15ac8b3ae73b8da2ffc74130b8e25b
--- src/lib9/debugmalloc.c
+++ src/lib9/debugmalloc.c
@@ -6,7 +6,6 @@
  * The Unix libc routines cannot be trusted to do their own locking.
  * Sad but apparently true.
  */
-static Lock malloclock;
 static int mallocpid;
 
 /*
@@ -112,11 +111,9 @@ p9malloc(ulong n)
 	if(n == 0)
 		n++;
 /*fprint(2, "%s %d malloc\n", argv0, getpid()); */
-	lock(&malloclock);
 	mallocpid = getpid();
 	v = malloc(n+Overhead);
 	v = mark(v, getcallerpc(&n), n, MallocMagic);
-	unlock(&malloclock);
 /*fprint(2, "%s %d donemalloc\n", argv0, getpid()); */
 	return v;
 }
@@ -128,11 +125,9 @@ p9free(void *v)
 		return;
 
 /*fprint(2, "%s %d free\n", argv0, getpid()); */
-	lock(&malloclock);
 	mallocpid = getpid();
 	v = mark(v, getcallerpc(&v), 0, FreeMagic);
 	free(v);
-	unlock(&malloclock);
 /*fprint(2, "%s %d donefree\n", argv0, getpid()); */
 }
 
@@ -142,11 +137,9 @@ p9calloc(ulong a, ulong b)
 	void *v;
 
 /*fprint(2, "%s %d calloc\n", argv0, getpid()); */
-	lock(&malloclock);
 	mallocpid = getpid();
 	v = calloc(a*b+Overhead, 1);
 	v = mark(v, getcallerpc(&a), a*b, CallocMagic);
-	unlock(&malloclock);
 /*fprint(2, "%s %d donecalloc\n", argv0, getpid()); */
 	return v;
 }
@@ -155,12 +148,10 @@ void*
 p9realloc(void *v, ulong n)
 {
 /*fprint(2, "%s %d realloc\n", argv0, getpid()); */
-	lock(&malloclock);
 	mallocpid = getpid();
 	v = mark(v, getcallerpc(&v), 0, CheckMagic);
 	v = realloc(v, n+Overhead);
 	v = mark(v, getcallerpc(&v), n, ReallocMagic);
-	unlock(&malloclock);
 /*fprint(2, "%s %d donerealloc\n", argv0, getpid()); */
 	return v;
 }
blob - 33593aa2f1889297ad847a400b8f45888e04dfc1
blob + 695ff8bc04529b709d6bd6319eb05d445008c41e
--- src/lib9/malloc.c
+++ src/lib9/malloc.c
@@ -7,50 +7,31 @@
 #define NOPLAN9DEFINES
 #include <libc.h>
 
-static Lock malloclock;
 
 void*
 p9malloc(ulong n)
 {
-	void *v;
-
 	if(n == 0)
 		n++;
-	lock(&malloclock);
-	v = malloc(n);
-	unlock(&malloclock);
-	return v;
+	return malloc(n);
 }
 
 void
 p9free(void *v)
 {
-	if(v == nil)
-		return;
-	lock(&malloclock);
 	free(v);
-	unlock(&malloclock);
 }
 
 void*
 p9calloc(ulong a, ulong b)
 {
-	void *v;
-
 	if(a*b == 0)
 		a = b = 1;
-
-	lock(&malloclock);
-	v = calloc(a*b, 1);
-	unlock(&malloclock);
-	return v;
+	return calloc(a, b);
 }
 
 void*
 p9realloc(void *v, ulong n)
 {
-	lock(&malloclock);
-	v = realloc(v, n);
-	unlock(&malloclock);
-	return v;
+	return realloc(v, n);
 }