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172 lines
5.8 KiB
172 lines
5.8 KiB
commit ece550d98e1c10017fb91ecfa0d19ae9d2dc45da
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Author: Willy Tarreau <w@1wt.eu>
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Date: Wed Aug 1 19:12:20 2018 +0200
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MINOR: threads: add more consistency between certain variables in no-thread case
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When threads are disabled, some variables such as tid and tid_bit are
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still checked everywhere, the MAX_THREADS_MASK macro is ~0UL while
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MAX_THREADS is 1, and the all_threads_mask variable is replaced with a
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macro forced to zero. The compiler cannot optimize away all this code
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involving checks on tid and tid_bit, and we end up in special cases
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where all_threads_mask has to be specifically tested for being zero or
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not. It is not even certain the code paths are always equivalent when
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testing without threads and with nbthread 1.
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Let's change this to make sure we always present a single thread when
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threads are disabled, and have the relevant values declared as constants
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so that the compiler can optimize all the tests away. Now we have
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MAX_THREADS_MASK set to 1, all_threads_mask set to 1, tid set to zero
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and tid_bit set to 1. Doing just this has removed 4 kB of code in the
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no-thread case.
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A few checks for all_threads_mask==0 have been removed since it never
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happens anymore.
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(cherry picked from commit 0c026f49e7348bce5b3c74be896ae208ae6e26a4)
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[wt: the thread code feels safer with this, especially with the small updates
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needed for the rdv point; missed one occurrence fixed by next patch]
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Signed-off-by: Willy Tarreau <w@1wt.eu>
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diff --git a/include/common/hathreads.h b/include/common/hathreads.h
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index 4e72848e..7eb5d127 100644
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--- a/include/common/hathreads.h
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+++ b/include/common/hathreads.h
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@@ -24,10 +24,6 @@
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#include <common/config.h>
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-#define MAX_THREADS_MASK ((unsigned long)-1)
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-extern THREAD_LOCAL unsigned int tid; /* The thread id */
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-extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the thread id */
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-
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/* Note about all_threads_mask :
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* - with threads support disabled, this symbol is defined as zero (0UL).
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* - with threads enabled, this variable is never zero, it contains the mask
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@@ -37,7 +33,14 @@ extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the threa
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#ifndef USE_THREAD
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#define MAX_THREADS 1
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-#define all_threads_mask 0UL
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+#define MAX_THREADS_MASK 1
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+
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+/* Only way found to replace variables with constants that are optimized away
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+ * at build time.
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+ */
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+enum { all_threads_mask = 1UL };
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+enum { tid_bit = 1UL };
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+enum { tid = 0 };
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#define __decl_hathreads(decl)
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@@ -98,6 +101,9 @@ extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the threa
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#define ha_sigmask(how, set, oldset) sigprocmask(how, set, oldset)
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+static inline void ha_set_tid(unsigned int tid)
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+{
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+}
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static inline void __ha_barrier_load(void)
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{
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@@ -120,6 +126,7 @@ static inline void __ha_barrier_full(void)
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#include <import/plock.h>
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#define MAX_THREADS LONGBITS
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+#define MAX_THREADS_MASK ((unsigned long)-1)
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#define __decl_hathreads(decl) decl
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@@ -223,10 +230,19 @@ void thread_exit_sync(void);
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int thread_no_sync(void);
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int thread_need_sync(void);
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+extern THREAD_LOCAL unsigned int tid; /* The thread id */
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+extern THREAD_LOCAL unsigned long tid_bit; /* The bit corresponding to the thread id */
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extern volatile unsigned long all_threads_mask;
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#define ha_sigmask(how, set, oldset) pthread_sigmask(how, set, oldset)
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+/* sets the thread ID and the TID bit for the current thread */
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+static inline void ha_set_tid(unsigned int data)
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+{
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+ tid = data;
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+ tid_bit = (1UL << tid);
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+}
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+
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#if defined(DEBUG_THREAD) || defined(DEBUG_FULL)
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diff --git a/src/cfgparse.c b/src/cfgparse.c
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index 24349a59..d1474d4b 100644
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--- a/src/cfgparse.c
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+++ b/src/cfgparse.c
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@@ -7652,11 +7652,11 @@ int check_config_validity()
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nbproc = my_ffsl(bind_conf->bind_proc);
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mask = bind_conf->bind_thread[nbproc - 1];
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- if (mask && !(mask & (all_threads_mask ? all_threads_mask : 1UL))) {
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+ if (mask && !(mask & all_threads_mask)) {
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unsigned long new_mask = 0;
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while (mask) {
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- new_mask |= mask & (all_threads_mask ? all_threads_mask : 1UL);
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+ new_mask |= mask & all_threads_mask;
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mask >>= global.nbthread;
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}
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diff --git a/src/haproxy.c b/src/haproxy.c
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index 9ba56623..e0186ff9 100644
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--- a/src/haproxy.c
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+++ b/src/haproxy.c
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@@ -2448,8 +2448,7 @@ static void *run_thread_poll_loop(void *data)
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struct per_thread_deinit_fct *ptdf;
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__decl_hathreads(static HA_SPINLOCK_T start_lock);
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- tid = *((unsigned int *)data);
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- tid_bit = (1UL << tid);
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+ ha_set_tid(*((unsigned int *)data));
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tv_update_date(-1,-1);
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list_for_each_entry(ptif, &per_thread_init_list, list) {
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diff --git a/src/hathreads.c b/src/hathreads.c
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index 0d0a0509..238cbb80 100644
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--- a/src/hathreads.c
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+++ b/src/hathreads.c
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@@ -19,8 +19,6 @@
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#include <common/standard.h>
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#include <proto/fd.h>
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-THREAD_LOCAL unsigned int tid = 0;
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-THREAD_LOCAL unsigned long tid_bit = (1UL << 0);
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/* Dummy I/O handler used by the sync pipe.*/
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void thread_sync_io_handler(int fd)
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@@ -33,6 +31,9 @@ static HA_SPINLOCK_T sync_lock;
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static int threads_sync_pipe[2];
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static unsigned long threads_want_sync = 0;
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volatile unsigned long all_threads_mask = 1; // nbthread 1 assumed by default
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+THREAD_LOCAL unsigned int tid = 0;
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+THREAD_LOCAL unsigned long tid_bit = (1UL << 0);
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+
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#if defined(DEBUG_THREAD) || defined(DEBUG_FULL)
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struct lock_stat lock_stats[LOCK_LABELS];
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@@ -130,7 +131,7 @@ void thread_enter_sync()
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{
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static volatile unsigned long barrier = 0;
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- if (!all_threads_mask)
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+ if (!(all_threads_mask & (all_threads_mask - 1)))
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return;
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thread_sync_barrier(&barrier);
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@@ -146,7 +147,7 @@ void thread_exit_sync()
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{
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static volatile unsigned long barrier = 0;
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- if (!all_threads_mask)
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+ if (!(all_threads_mask & (all_threads_mask - 1)))
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return;
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if (threads_want_sync & tid_bit)
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