X-Git-Url: http://git.openwrt.org/?p=openwrt%2Fopenwrt.git;a=blobdiff_plain;f=toolchain%2Fmusl%2Fpatches%2F500-0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch;fp=toolchain%2Fmusl%2Fpatches%2F500-0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch;h=0000000000000000000000000000000000000000;hp=4ca51b0be0a2b1f12b5cc48765a5e485aa9c81fd;hb=aaec2ad13b18086e2aaf9ca9152827c50e578bc0;hpb=da5bb885e17cf77caea70adcf473f1fb95448553;ds=sidebyside

diff --git a/toolchain/musl/patches/500-0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch b/toolchain/musl/patches/500-0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch
deleted file mode 100644
index 4ca51b0be0..0000000000
--- a/toolchain/musl/patches/500-0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch
+++ /dev/null
@@ -1,69 +0,0 @@
-From e01b5939b38aea5ecbe41670643199825874b26c Mon Sep 17 00:00:00 2001
-From: Rich Felker <dalias@aerifal.cx>
-Date: Thu, 21 May 2020 23:32:45 -0400
-Subject: [PATCH 2/4] don't use libc.threads_minus_1 as relaxed atomic for
- skipping locks
-
-after all but the last thread exits, the next thread to observe
-libc.threads_minus_1==0 and conclude that it can skip locking fails to
-synchronize with any changes to memory that were made by the
-last-exiting thread. this can produce data races.
-
-on some archs, at least x86, memory synchronization is unlikely to be
-a problem; however, with the inline locks in malloc, skipping the lock
-also eliminated the compiler barrier, and caused code that needed to
-re-check chunk in-use bits after obtaining the lock to reuse a stale
-value, possibly from before the process became single-threaded. this
-in turn produced corruption of the heap state.
-
-some uses of libc.threads_minus_1 remain, especially for allocation of
-new TLS in the dynamic linker; otherwise, it could be removed
-entirely. it's made non-volatile to reflect that the remaining
-accesses are only made under lock on the thread list.
-
-instead of libc.threads_minus_1, libc.threaded is now used for
-skipping locks. the difference is that libc.threaded is permanently
-true once an additional thread has been created. this will produce
-some performance regression in processes that are mostly
-single-threaded but occasionally creating threads. in the future it
-may be possible to bring back the full lock-skipping, but more care
-needs to be taken to produce a safe design.
----
- src/internal/libc.h | 2 +-
- src/malloc/malloc.c | 2 +-
- src/thread/__lock.c | 2 +-
- 3 files changed, 3 insertions(+), 3 deletions(-)
-
---- a/src/internal/libc.h
-+++ b/src/internal/libc.h
-@@ -21,7 +21,7 @@ struct __libc {
- 	int can_do_threads;
- 	int threaded;
- 	int secure;
--	volatile int threads_minus_1;
-+	int threads_minus_1;
- 	size_t *auxv;
- 	struct tls_module *tls_head;
- 	size_t tls_size, tls_align, tls_cnt;
---- a/src/malloc/malloc.c
-+++ b/src/malloc/malloc.c
-@@ -26,7 +26,7 @@ int __malloc_replaced;
- 
- static inline void lock(volatile int *lk)
- {
--	if (libc.threads_minus_1)
-+	if (libc.threaded)
- 		while(a_swap(lk, 1)) __wait(lk, lk+1, 1, 1);
- }
- 
---- a/src/thread/__lock.c
-+++ b/src/thread/__lock.c
-@@ -18,7 +18,7 @@
- 
- void __lock(volatile int *l)
- {
--	if (!libc.threads_minus_1) return;
-+	if (!libc.threaded) return;
- 	/* fast path: INT_MIN for the lock, +1 for the congestion */
- 	int current = a_cas(l, 0, INT_MIN + 1);
- 	if (!current) return;