From 0bd67bbfbccb7a2a2212276454e60214d637370b Mon Sep 17 00:00:00 2001 From: Jeremy Allison Date: Tue, 3 Jun 2014 10:44:19 -0700 Subject: [PATCH] lib: tevent: make TEVENT_SIG_INCREMENT atomic. On arm platforms incrementing a variable is not an atomic operation, so may be interrupted by signal processing (if a signal interrups another signal handler). Use compiler built-ins to make this atomic. __sync_fetch_and_add() works on gcc, llvm, IBM xlC on AIX, and Intel icc (10.1 and above). atomic_add_32() works on Oracle Solaris. Based on an inital patch from kamei@osstech.co.jp. Bug #10640 - smbd is not responding - tevent_common_signal_handler() increments non-atomic variables https://bugzilla.samba.org/show_bug.cgi?id=10640 Signed-off-by: Jeremy Allison --- lib/replace/replace.h | 5 +++++ lib/replace/wscript | 25 +++++++++++++++++++++++++ lib/tevent/tevent_signal.c | 6 ++++++ 3 files changed, 36 insertions(+) diff --git a/lib/replace/replace.h b/lib/replace/replace.h index f940898..bc40bf0 100644 --- a/lib/replace/replace.h +++ b/lib/replace/replace.h @@ -904,4 +904,9 @@ bool nss_wrapper_hosts_enabled(void); bool socket_wrapper_enabled(void); bool uid_wrapper_enabled(void); +/* Needed for Solaris atomic_add_XX functions. */ +#if defined(HAVE_SYS_ATOMIC_H) +#include +#endif + #endif /* _LIBREPLACE_REPLACE_H */ diff --git a/lib/replace/wscript b/lib/replace/wscript index a26de0f..22dd132 100644 --- a/lib/replace/wscript +++ b/lib/replace/wscript @@ -110,6 +110,7 @@ struct foo bar = { .y = 'X', .x = 1 }; conf.CHECK_HEADERS('sys/extattr.h sys/ea.h sys/proplist.h sys/cdefs.h') conf.CHECK_HEADERS('utmp.h utmpx.h lastlog.h malloc.h') conf.CHECK_HEADERS('syscall.h sys/syscall.h inttypes.h') + conf.CHECK_HEADERS('sys/atomic.h') # Check for process set name support conf.CHECK_CODE(''' @@ -229,6 +230,30 @@ struct foo bar = { .y = 'X', .x = 1 }; msg="Checking whether we have ucontext_t", headers='signal.h sys/ucontext.h') + # Check for atomic builtins. */ + conf.CHECK_CODE(''' + int main(void) { + int i; + (void)__sync_fetch_and_add(&i, 1); + return 0; + } + ''', + 'HAVE___SYNC_FETCH_AND_ADD', + msg='Checking for __sync_fetch_and_add compiler builtin') + + conf.CHECK_CODE(''' + #include + #include + int main(void) { + int32_t i; + atomic_add_32(&i, 1); + return 0; + } + ''', + 'HAVE_ATOMIC_ADD_32', + headers='stdint.h sys/atomic.h', + msg='Checking for atomic_add_32 compiler builtin') + # these may be builtins, so we need the link=False strategy conf.CHECK_FUNCS('strdup memmem printf memset memcpy memmove strcpy strncpy bzero', link=False) diff --git a/lib/tevent/tevent_signal.c b/lib/tevent/tevent_signal.c index 1ff4872..b54da2e 100644 --- a/lib/tevent/tevent_signal.c +++ b/lib/tevent/tevent_signal.c @@ -52,7 +52,13 @@ struct tevent_sigcounter { uint32_t seen; }; +#if defined(HAVE___SYNC_FETCH_AND_ADD) +#define TEVENT_SIG_INCREMENT(s) __sync_fetch_and_add(&((s).count), 1) +#elif defined(HAVE_ATOMIC_ADD_32) +#define TEVENT_SIG_INCREMENT(s) atomic_add_32(&((s).count), 1) +#else #define TEVENT_SIG_INCREMENT(s) (s).count++ +#endif #define TEVENT_SIG_SEEN(s, n) (s).seen += (n) #define TEVENT_SIG_PENDING(s) ((s).seen != (s).count) -- 1.9.1.423.g4596e3a