diff options
6 files changed, 275 insertions, 73 deletions
diff --git a/main/musl/0001-reorder-thread-list-unlink-in-pthread_exit-after-all.patch b/main/musl/0001-reorder-thread-list-unlink-in-pthread_exit-after-all.patch new file mode 100644 index 00000000000..2706d1516ab --- /dev/null +++ b/main/musl/0001-reorder-thread-list-unlink-in-pthread_exit-after-all.patch @@ -0,0 +1,56 @@ +From 4d5aa20a94a2d3fae3e69289dc23ecafbd0c16c4 Mon Sep 17 00:00:00 2001 +From: Rich Felker <dalias@aerifal.cx> +Date: Fri, 22 May 2020 17:35:14 -0400 +Subject: [PATCH 1/4] reorder thread list unlink in pthread_exit after all + locks + +since the backend for LOCK() skips locking if single-threaded, it's +unsafe to make the process appear single-threaded before the last use +of lock. + +this fixes potential unsynchronized access to a linked list via +__dl_thread_cleanup. +--- + src/thread/pthread_create.c | 19 +++++++++++-------- + 1 file changed, 11 insertions(+), 8 deletions(-) + +diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c +index 5f491092..6a3b0c21 100644 +--- a/src/thread/pthread_create.c ++++ b/src/thread/pthread_create.c +@@ -90,14 +90,7 @@ _Noreturn void __pthread_exit(void *result) + exit(0); + } + +- /* At this point we are committed to thread termination. Unlink +- * the thread from the list. This change will not be visible +- * until the lock is released, which only happens after SYS_exit +- * has been called, via the exit futex address pointing at the lock. */ +- libc.threads_minus_1--; +- self->next->prev = self->prev; +- self->prev->next = self->next; +- self->prev = self->next = self; ++ /* At this point we are committed to thread termination. */ + + /* Process robust list in userspace to handle non-pshared mutexes + * and the detached thread case where the robust list head will +@@ -121,6 +114,16 @@ _Noreturn void __pthread_exit(void *result) + __do_orphaned_stdio_locks(); + __dl_thread_cleanup(); + ++ /* Last, unlink thread from the list. This change will not be visible ++ * until the lock is released, which only happens after SYS_exit ++ * has been called, via the exit futex address pointing at the lock. ++ * This needs to happen after any possible calls to LOCK() that might ++ * skip locking if libc.threads_minus_1 is zero. */ ++ libc.threads_minus_1--; ++ self->next->prev = self->prev; ++ self->prev->next = self->next; ++ self->prev = self->next = self; ++ + /* This atomic potentially competes with a concurrent pthread_detach + * call; the loser is responsible for freeing thread resources. */ + int state = a_cas(&self->detach_state, DT_JOINABLE, DT_EXITING); +-- +2.21.0 + diff --git a/main/musl/0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch b/main/musl/0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch new file mode 100644 index 00000000000..370667fe521 --- /dev/null +++ b/main/musl/0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch @@ -0,0 +1,78 @@ +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(-) + +diff --git a/src/internal/libc.h b/src/internal/libc.h +index ac97dc7e..c0614852 100644 +--- 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; +diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c +index 96982596..2553a62e 100644 +--- 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); + } + +diff --git a/src/thread/__lock.c b/src/thread/__lock.c +index 45557c88..5b9b144e 100644 +--- 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; +-- +2.21.0 + diff --git a/main/musl/0003-cut-down-size-of-some-libc-struct-members.patch b/main/musl/0003-cut-down-size-of-some-libc-struct-members.patch new file mode 100644 index 00000000000..b9e32db8f7c --- /dev/null +++ b/main/musl/0003-cut-down-size-of-some-libc-struct-members.patch @@ -0,0 +1,30 @@ +From f12888e9eb9eed60cc266b899dcafecb4752964a Mon Sep 17 00:00:00 2001 +From: Rich Felker <dalias@aerifal.cx> +Date: Fri, 22 May 2020 17:25:38 -0400 +Subject: [PATCH 3/4] cut down size of some libc struct members + +these are all flags that can be single-byte values. +--- + src/internal/libc.h | 6 +++--- + 1 file changed, 3 insertions(+), 3 deletions(-) + +diff --git a/src/internal/libc.h b/src/internal/libc.h +index c0614852..d47f58e0 100644 +--- a/src/internal/libc.h ++++ b/src/internal/libc.h +@@ -18,9 +18,9 @@ struct tls_module { + }; + + struct __libc { +- int can_do_threads; +- int threaded; +- int secure; ++ char can_do_threads; ++ char threaded; ++ char secure; + int threads_minus_1; + size_t *auxv; + struct tls_module *tls_head; +-- +2.21.0 + diff --git a/main/musl/0004-restore-lock-skipping-for-processes-that-return-to-s.patch b/main/musl/0004-restore-lock-skipping-for-processes-that-return-to-s.patch new file mode 100644 index 00000000000..b30bd497724 --- /dev/null +++ b/main/musl/0004-restore-lock-skipping-for-processes-that-return-to-s.patch @@ -0,0 +1,101 @@ +From 8d81ba8c0bc6fe31136cb15c9c82ef4c24965040 Mon Sep 17 00:00:00 2001 +From: Rich Felker <dalias@aerifal.cx> +Date: Fri, 22 May 2020 17:45:47 -0400 +Subject: [PATCH 4/4] restore lock-skipping for processes that return to + single-threaded state + +the design used here relies on the barrier provided by the first lock +operation after the process returns to single-threaded state to +synchronize with actions by the last thread that exited. by storing +the intent to change modes in the same object used to detect whether +locking is needed, it's possible to avoid an extra (possibly costly) +memory load after the lock is taken. +--- + src/internal/libc.h | 1 + + src/malloc/malloc.c | 5 ++++- + src/thread/__lock.c | 4 +++- + src/thread/pthread_create.c | 8 ++++---- + 4 files changed, 12 insertions(+), 6 deletions(-) + +diff --git a/src/internal/libc.h b/src/internal/libc.h +index d47f58e0..619bba86 100644 +--- a/src/internal/libc.h ++++ b/src/internal/libc.h +@@ -21,6 +21,7 @@ struct __libc { + char can_do_threads; + char threaded; + char secure; ++ volatile signed char need_locks; + int threads_minus_1; + size_t *auxv; + struct tls_module *tls_head; +diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c +index 2553a62e..a803d4c9 100644 +--- a/src/malloc/malloc.c ++++ b/src/malloc/malloc.c +@@ -26,8 +26,11 @@ int __malloc_replaced; + + static inline void lock(volatile int *lk) + { +- if (libc.threaded) ++ int need_locks = libc.need_locks; ++ if (need_locks) { + while(a_swap(lk, 1)) __wait(lk, lk+1, 1, 1); ++ if (need_locks < 0) libc.need_locks = 0; ++ } + } + + static inline void unlock(volatile int *lk) +diff --git a/src/thread/__lock.c b/src/thread/__lock.c +index 5b9b144e..60eece49 100644 +--- a/src/thread/__lock.c ++++ b/src/thread/__lock.c +@@ -18,9 +18,11 @@ + + void __lock(volatile int *l) + { +- if (!libc.threaded) return; ++ int need_locks = libc.need_locks; ++ if (!need_locks) return; + /* fast path: INT_MIN for the lock, +1 for the congestion */ + int current = a_cas(l, 0, INT_MIN + 1); ++ if (need_locks < 0) libc.need_locks = 0; + if (!current) return; + /* A first spin loop, for medium congestion. */ + for (unsigned i = 0; i < 10; ++i) { +diff --git a/src/thread/pthread_create.c b/src/thread/pthread_create.c +index 6a3b0c21..6bdfb44f 100644 +--- a/src/thread/pthread_create.c ++++ b/src/thread/pthread_create.c +@@ -118,8 +118,8 @@ _Noreturn void __pthread_exit(void *result) + * until the lock is released, which only happens after SYS_exit + * has been called, via the exit futex address pointing at the lock. + * This needs to happen after any possible calls to LOCK() that might +- * skip locking if libc.threads_minus_1 is zero. */ +- libc.threads_minus_1--; ++ * skip locking if process appears single-threaded. */ ++ if (!--libc.threads_minus_1) libc.need_locks = -1; + self->next->prev = self->prev; + self->prev->next = self->next; + self->prev = self->next = self; +@@ -339,7 +339,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att + ~(1UL<<((SIGCANCEL-1)%(8*sizeof(long)))); + + __tl_lock(); +- libc.threads_minus_1++; ++ if (!libc.threads_minus_1++) libc.need_locks = 1; + ret = __clone((c11 ? start_c11 : start), stack, flags, args, &new->tid, TP_ADJ(new), &__thread_list_lock); + + /* All clone failures translate to EAGAIN. If explicit scheduling +@@ -363,7 +363,7 @@ int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict att + new->next->prev = new; + new->prev->next = new; + } else { +- libc.threads_minus_1--; ++ if (!--libc.threads_minus_1) libc.need_locks = 0; + } + __tl_unlock(); + __restore_sigs(&set); +-- +2.21.0 + diff --git a/main/musl/APKBUILD b/main/musl/APKBUILD index c68fe9eff75..e00c18db4cb 100644 --- a/main/musl/APKBUILD +++ b/main/musl/APKBUILD @@ -2,7 +2,7 @@ # Maintainer: Timo Teräs <timo.teras@iki.fi> pkgname=musl pkgver=1.1.24 -pkgrel=8 +pkgrel=9 pkgdesc="the musl c library (libc) implementation" url="https://musl.libc.org/" arch="all" @@ -31,7 +31,11 @@ source="https://musl.libc.org/releases/musl-$pkgver.tar.gz ppc64-fpregset_t.patch fix-remaining-direct-use-of-stat-syscalls-outside.patch set-AD-bit-in-dns-queries-suppress-for-internal-use.patch - dont-use-threads-minus-1-for-skipping-locks.patch + + 0001-reorder-thread-list-unlink-in-pthread_exit-after-all.patch + 0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch + 0003-cut-down-size-of-some-libc-struct-members.patch + 0004-restore-lock-skipping-for-processes-that-return-to-s.patch ldconfig __stack_chk_fail_local.c @@ -187,7 +191,10 @@ e7133ce2f0b172e2da03567e41f03bef58b6ff8eaac614494751228bcc102c39cbe312f0beb567c5 3de8e50519e33a55d2cc737b56011a7178d1c83230477d46e11e67195e08e74bff735c6013de6ff170bb2390e89bfca9919cc8728c064b3eeaab2035dd7e5c08 ppc64-fpregset_t.patch d277e45af78ed2bd9f556ae30636783fc401b4d0a339d6e37b77f18ed1486f48fc631e3455f8764ddbc7d9aba41a270ab345ec3495955dfd22b27a306441ba2a fix-remaining-direct-use-of-stat-syscalls-outside.patch dd46ef77b71d34b6207611be59dd4555b4e53fd7169732b9e5ee9a66f1e8da69fcca6634f895b9d34d8861d37ac0eaa86618f5f3f3a81cf9c47321d1c5d37ee5 set-AD-bit-in-dns-queries-suppress-for-internal-use.patch -1372f9ddcfd48df8929ea5af76dd5e806f89c9d7b70b8a19b8480987b7fab5632e939370f4160cd2c132549cfcda0f4470ad5b2d46f74fd615ef1e9f2f77a72c dont-use-threads-minus-1-for-skipping-locks.patch +0bb30198e92d26058f98f28be31bb8cee89a699e9fa9377315c9a86f504708ddb432d579bebfd4429da3fd5e6832e4166aa80d4d3f08658702206474fd1a8ffe 0001-reorder-thread-list-unlink-in-pthread_exit-after-all.patch +c6cd692359961c382b7382c6eb819bf93ca8d687b7bd71e4d992acabc7003bd8388b22898059b6ac5abdf08c07020c8cbd2a5f908802258418079e096cdbc058 0002-don-t-use-libc.threads_minus_1-as-relaxed-atomic-for.patch +416aa17d4211ebbca97b4ce47eea8d8375ac5e0b602a4806175bc172be21b8291ac08fdaf39203e3a083a067bbbfa999cfb875f739d5fa07871885ac02eba75a 0003-cut-down-size-of-some-libc-struct-members.patch +f0e5ab79a793152c5e6c1c560b409ef062c8f9232c893b36c58b9667e5e0e86969555d8e2e9e17b59835ec7ed3c926a6ccce453824561ad82e47364c44374549 0004-restore-lock-skipping-for-processes-that-return-to-s.patch 8d3a2d5315fc56fee7da9abb8b89bb38c6046c33d154c10d168fb35bfde6b0cf9f13042a3bceee34daf091bc409d699223735dcf19f382eeee1f6be34154f26f ldconfig 062bb49fa54839010acd4af113e20f7263dde1c8a2ca359b5fb2661ef9ed9d84a0f7c3bc10c25dcfa10bb3c5a4874588dff636ac43d5dbb3d748d75400756d0b __stack_chk_fail_local.c 0d80f37b34a35e3d14b012257c50862dfeb9d2c81139ea2dfa101d981d093b009b9fa450ba27a708ac59377a48626971dfc58e20a3799084a65777a0c32cbc7d getconf.c diff --git a/main/musl/dont-use-threads-minus-1-for-skipping-locks.patch b/main/musl/dont-use-threads-minus-1-for-skipping-locks.patch deleted file mode 100644 index 6d40ebacf41..00000000000 --- a/main/musl/dont-use-threads-minus-1-for-skipping-locks.patch +++ /dev/null @@ -1,70 +0,0 @@ -commit cbcb082e045e28abce2b3f72e922c6ccdcb96c06 -Author: Rich Felker <dalias@aerifal.cx> -Date: Thu May 21 23:32:45 2020 -0400 - - 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. - -diff --git a/src/internal/libc.h b/src/internal/libc.h -index ac97dc7e..c0614852 100644 ---- 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; -diff --git a/src/malloc/malloc.c b/src/malloc/malloc.c -index 96982596..2553a62e 100644 ---- 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); - } - -diff --git a/src/thread/__lock.c b/src/thread/__lock.c -index 45557c88..5b9b144e 100644 ---- 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; |