Date: Tue, 24 Jan 2017 11:13:41 +0000 (UTC) From: Konstantin Belousov <kib@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r312693 - stable/11/libexec/rtld-elf Message-ID: <201701241113.v0OBDfkU069370@repo.freebsd.org>
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Author: kib Date: Tue Jan 24 11:13:41 2017 New Revision: 312693 URL: https://svnweb.freebsd.org/changeset/base/312693 Log: MFC r311886: Fix acquisition of nested write compat rtld locks. PR: 215826 Modified: stable/11/libexec/rtld-elf/rtld_lock.c Directory Properties: stable/11/ (props changed) Modified: stable/11/libexec/rtld-elf/rtld_lock.c ============================================================================== --- stable/11/libexec/rtld-elf/rtld_lock.c Tue Jan 24 10:42:21 2017 (r312692) +++ stable/11/libexec/rtld-elf/rtld_lock.c Tue Jan 24 11:13:41 2017 (r312693) @@ -64,7 +64,7 @@ typedef struct Struct_Lock { } Lock; static sigset_t fullsigmask, oldsigmask; -static int thread_flag; +static int thread_flag, wnested; static void * def_lock_create(void) @@ -117,29 +117,34 @@ def_rlock_acquire(void *lock) static void def_wlock_acquire(void *lock) { - Lock *l = (Lock *)lock; - sigset_t tmp_oldsigmask; + Lock *l; + sigset_t tmp_oldsigmask; - for ( ; ; ) { - sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask); - if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG)) - break; - sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL); - } - oldsigmask = tmp_oldsigmask; + l = (Lock *)lock; + for (;;) { + sigprocmask(SIG_BLOCK, &fullsigmask, &tmp_oldsigmask); + if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG)) + break; + sigprocmask(SIG_SETMASK, &tmp_oldsigmask, NULL); + } + if (atomic_fetchadd_int(&wnested, 1) == 0) + oldsigmask = tmp_oldsigmask; } static void def_lock_release(void *lock) { - Lock *l = (Lock *)lock; + Lock *l; - if ((l->lock & WAFLAG) == 0) - atomic_add_rel_int(&l->lock, -RC_INCR); - else { - atomic_add_rel_int(&l->lock, -WAFLAG); - sigprocmask(SIG_SETMASK, &oldsigmask, NULL); - } + l = (Lock *)lock; + if ((l->lock & WAFLAG) == 0) + atomic_add_rel_int(&l->lock, -RC_INCR); + else { + assert(wnested > 0); + atomic_add_rel_int(&l->lock, -WAFLAG); + if (atomic_fetchadd_int(&wnested, -1) == 1) + sigprocmask(SIG_SETMASK, &oldsigmask, NULL); + } } static int @@ -373,12 +378,12 @@ _rtld_atfork_pre(int *locks) return; /* - * Warning: this does not work with the rtld compat locks - * above, since the thread signal mask is corrupted (set to - * all signals blocked) if two locks are taken in write mode. - * The caller of the _rtld_atfork_pre() must provide the - * working implementation of the locks, and libthr locks are - * fine. + * Warning: this did not worked well with the rtld compat + * locks above, when the thread signal mask was corrupted (set + * to all signals blocked) if two locks were taken + * simultaneously in the write mode. The caller of the + * _rtld_atfork_pre() must provide the working implementation + * of the locks anyway, and libthr locks are fine. */ wlock_acquire(rtld_phdr_lock, &ls[0]); wlock_acquire(rtld_bind_lock, &ls[1]);
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