fix: removal of [smp_]read_barrier_depends (v5.9)

See upstream commits:

  commit 76ebbe78f7390aee075a7f3768af197ded1bdfbb
  Author: Will Deacon <will@kernel.org>
  Date:   Tue Oct 24 11:22:47 2017 +0100

    locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()

    In preparation for the removal of lockless_dereference(), which is the
    same as READ_ONCE() on all architectures other than Alpha, add an
    implicit smp_read_barrier_depends() to READ_ONCE() so that it can be
    used to head dependency chains on all architectures.

  commit 76ebbe78f7390aee075a7f3768af197ded1bdfbb
  Author: Will Deacon <will.deacon@arm.com>
  Date:   Tue Oct 24 11:22:47 2017 +0100

    locking/barriers: Add implicit smp_read_barrier_depends() to READ_ONCE()

    In preparation for the removal of lockless_dereference(), which is the
    same as READ_ONCE() on all architectures other than Alpha, add an
    implicit smp_read_barrier_depends() to READ_ONCE() so that it can be
    used to head dependency chains on all architectures.

Change-Id: Ife8880bd9378dca2972da8838f40fc35ccdfaaac
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/instrumentation/events/lttng-module/i2c.h b/instrumentation/events/lttng-module/i2c.h
index dcbabf6ffb65be9e45f1d5395e3c57a73e9d9245..131d1344e54dc57190ef017e75892cb389d06429 100644 (file)
--- a/instrumentation/events/lttng-module/i2c.h
+++ b/instrumentation/events/lttng-module/i2c.h
@@ -23,7 +23,7 @@ LTTNG_TRACEPOINT_EVENT_CODE(i2c_write,
 
        TP_code_pre(
                tp_locvar->extract_sensitive_payload =
-                       READ_ONCE(extract_sensitive_payload);
+                       LTTNG_READ_ONCE(extract_sensitive_payload);
        ),
 
        TP_FIELDS(
@@ -78,7 +78,7 @@ LTTNG_TRACEPOINT_EVENT_CODE(i2c_reply,
 
        TP_code_pre(
                tp_locvar->extract_sensitive_payload =
-                       READ_ONCE(extract_sensitive_payload);
+                       LTTNG_READ_ONCE(extract_sensitive_payload);
        ),
 
        TP_FIELDS(

diff --git a/lib/ringbuffer/backend.h b/lib/ringbuffer/backend.h
index da937f29d6f8cc3c8954ca4be7361e9f7e003139..43e1d47542d3140183bf80cc725dfa0d77e29257 100644 (file)
--- a/lib/ringbuffer/backend.h
+++ b/lib/ringbuffer/backend.h
@@ -156,7 +156,7 @@ size_t lib_ring_buffer_do_strcpy(const struct lib_ring_buffer_config *config,
                 * Only read source character once, in case it is
                 * modified concurrently.
                 */
-               c = READ_ONCE(src[count]);
+               c = LTTNG_READ_ONCE(src[count]);
                if (!c)
                        break;
                lib_ring_buffer_do_copy(config, &dest[count], &c, 1);

diff --git a/lib/ringbuffer/backend_internal.h b/lib/ringbuffer/backend_internal.h
index 2d6a3453103af434ed1d94ac66026eddd9cf342f..1226fd8f16acb2cb165b1df542695681899258dd 100644 (file)
--- a/lib/ringbuffer/backend_internal.h
+++ b/lib/ringbuffer/backend_internal.h
@@ -367,7 +367,7 @@ void lib_ring_buffer_clear_noref(const struct lib_ring_buffer_config *config,
         * Performing a volatile access to read the sb_pages, because we want to
         * read a coherent version of the pointer and the associated noref flag.
         */
-       id = READ_ONCE(bufb->buf_wsb[idx].id);
+       id = LTTNG_READ_ONCE(bufb->buf_wsb[idx].id);
        for (;;) {
                /* This check is called on the fast path for each record. */
                if (likely(!subbuffer_id_is_noref(config, id))) {

diff --git a/lib/ringbuffer/frontend.h b/lib/ringbuffer/frontend.h
index 6f516d989d2add911dd186c7ea3e316f1522a883..41382fe816d8a8643052fd28ddf242b4db9beb9a 100644 (file)
--- a/lib/ringbuffer/frontend.h
+++ b/lib/ringbuffer/frontend.h
@@ -79,7 +79,7 @@ void *channel_destroy(struct channel *chan);
 #define for_each_channel_cpu(cpu, chan)                                        \
        for ((cpu) = -1;                                                \
                ({ (cpu) = cpumask_next(cpu, (chan)->backend.cpumask);  \
-                  smp_read_barrier_depends(); (cpu) < nr_cpu_ids; });)
+                  smp_rmb(); (cpu) < nr_cpu_ids; });)
 
 extern struct lib_ring_buffer *channel_get_ring_buffer(
                                const struct lib_ring_buffer_config *config,
@@ -155,7 +155,7 @@ static inline
 int lib_ring_buffer_is_finalized(const struct lib_ring_buffer_config *config,
                                 struct lib_ring_buffer *buf)
 {
-       int finalized = READ_ONCE(buf->finalized);
+       int finalized = LTTNG_READ_ONCE(buf->finalized);
        /*
         * Read finalized before counters.
         */

diff --git a/lib/ringbuffer/ring_buffer_frontend.c b/lib/ringbuffer/ring_buffer_frontend.c
index 3cab365264e87431530c449648b8a9d6314449e4..4980d20ec8be522ee3967e9fa2c95d7968eb8073 100644 (file)
--- a/lib/ringbuffer/ring_buffer_frontend.c
+++ b/lib/ringbuffer/ring_buffer_frontend.c
@@ -1074,7 +1074,7 @@ int lib_ring_buffer_snapshot(struct lib_ring_buffer *buf,
        int finalized;
 
 retry:
-       finalized = READ_ONCE(buf->finalized);
+       finalized = LTTNG_READ_ONCE(buf->finalized);
        /*
         * Read finalized before counters.
         */
@@ -1245,7 +1245,7 @@ int lib_ring_buffer_get_subbuf(struct lib_ring_buffer *buf,
                return -EBUSY;
        }
 retry:
-       finalized = READ_ONCE(buf->finalized);
+       finalized = LTTNG_READ_ONCE(buf->finalized);
        /*
         * Read finalized before counters.
         */

diff --git a/lib/ringbuffer/ring_buffer_iterator.c b/lib/ringbuffer/ring_buffer_iterator.c
index d25db72502756b96a7bc3d65ebb33da635436023..7b4f20a5a2083d01c9ff70734ec9d38655edb33b 100644 (file)
--- a/lib/ringbuffer/ring_buffer_iterator.c
+++ b/lib/ringbuffer/ring_buffer_iterator.c
@@ -46,7 +46,7 @@ restart:
        switch (iter->state) {
        case ITER_GET_SUBBUF:
                ret = lib_ring_buffer_get_next_subbuf(buf);
-               if (ret && !READ_ONCE(buf->finalized)
+               if (ret && !LTTNG_READ_ONCE(buf->finalized)
                    && config->alloc == RING_BUFFER_ALLOC_GLOBAL) {
                        /*
                         * Use "pull" scheme for global buffers. The reader

diff --git a/lttng-events.c b/lttng-events.c
index be7e389702dbfbaccaabc85ed75f779905d8c202..d7192947719e3ee51fb78e630371344f03204b71 100644 (file)
--- a/lttng-events.c
+++ b/lttng-events.c
@@ -1719,7 +1719,7 @@ int lttng_metadata_printf(struct lttng_session *session,
        size_t len;
        va_list ap;
 
-       WARN_ON_ONCE(!READ_ONCE(session->active));
+       WARN_ON_ONCE(!LTTNG_READ_ONCE(session->active));
 
        va_start(ap, fmt);
        str = kvasprintf(GFP_KERNEL, fmt, ap);
@@ -2305,7 +2305,7 @@ int _lttng_event_metadata_statedump(struct lttng_session *session,
 {
        int ret = 0;
 
-       if (event->metadata_dumped || !READ_ONCE(session->active))
+       if (event->metadata_dumped || !LTTNG_READ_ONCE(session->active))
                return 0;
        if (chan->channel_type == METADATA_CHANNEL)
                return 0;
@@ -2377,7 +2377,7 @@ int _lttng_channel_metadata_statedump(struct lttng_session *session,
 {
        int ret = 0;
 
-       if (chan->metadata_dumped || !READ_ONCE(session->active))
+       if (chan->metadata_dumped || !LTTNG_READ_ONCE(session->active))
                return 0;
 
        if (chan->channel_type == METADATA_CHANNEL)
@@ -2604,7 +2604,7 @@ int _lttng_session_metadata_statedump(struct lttng_session *session)
        struct lttng_event *event;
        int ret = 0;
 
-       if (!READ_ONCE(session->active))
+       if (!LTTNG_READ_ONCE(session->active))
                return 0;
 
        lttng_metadata_begin(session);

diff --git a/probes/lttng-kprobes.c b/probes/lttng-kprobes.c
index a44eaa11d7a1d0a4ffcdabd5880d69622c126994..38fb72e89133fa7a4e573736b1a61de126288de8 100644 (file)
--- a/probes/lttng-kprobes.c
+++ b/probes/lttng-kprobes.c
@@ -31,11 +31,11 @@ int lttng_kprobes_handler_pre(struct kprobe *p, struct pt_regs *regs)
        int ret;
        unsigned long data = (unsigned long) p->addr;
 
-       if (unlikely(!READ_ONCE(chan->session->active)))
+       if (unlikely(!LTTNG_READ_ONCE(chan->session->active)))
                return 0;
-       if (unlikely(!READ_ONCE(chan->enabled)))
+       if (unlikely(!LTTNG_READ_ONCE(chan->enabled)))
                return 0;
-       if (unlikely(!READ_ONCE(event->enabled)))
+       if (unlikely(!LTTNG_READ_ONCE(event->enabled)))
                return 0;
 
        lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx, sizeof(data),

diff --git a/probes/lttng-kretprobes.c b/probes/lttng-kretprobes.c
index ab98ff221d85b0f1bd5c7c3242927d747c33f5fb..a6bcd21883468929378d556eac1a14209c95d661 100644 (file)
--- a/probes/lttng-kretprobes.c
+++ b/probes/lttng-kretprobes.c
@@ -51,11 +51,11 @@ int _lttng_kretprobes_handler(struct kretprobe_instance *krpi,
                unsigned long parent_ip;
        } payload;
 
-       if (unlikely(!READ_ONCE(chan->session->active)))
+       if (unlikely(!LTTNG_READ_ONCE(chan->session->active)))
                return 0;
-       if (unlikely(!READ_ONCE(chan->enabled)))
+       if (unlikely(!LTTNG_READ_ONCE(chan->enabled)))
                return 0;
-       if (unlikely(!READ_ONCE(event->enabled)))
+       if (unlikely(!LTTNG_READ_ONCE(event->enabled)))
                return 0;
 
        payload.ip = (unsigned long) krpi->rp->kp.addr;

diff --git a/probes/lttng-tracepoint-event-impl.h b/probes/lttng-tracepoint-event-impl.h
index 77b8638971dfec2d559d49d2f6c81e83bc2a2efe..72a669e929d91f3415f8ae72c0ea492e14958df1 100644 (file)
--- a/probes/lttng-tracepoint-event-impl.h
+++ b/probes/lttng-tracepoint-event-impl.h
@@ -1132,11 +1132,11 @@ static void __event_probe__##_name(void *__data, _proto)                      \
                                                                              \
        if (!_TP_SESSION_CHECK(session, __session))                           \
                return;                                                       \
-       if (unlikely(!READ_ONCE(__session->active)))                          \
+       if (unlikely(!LTTNG_READ_ONCE(__session->active)))                    \
                return;                                                       \
-       if (unlikely(!READ_ONCE(__chan->enabled)))                            \
+       if (unlikely(!LTTNG_READ_ONCE(__chan->enabled)))                      \
                return;                                                       \
-       if (unlikely(!READ_ONCE(__event->enabled)))                           \
+       if (unlikely(!LTTNG_READ_ONCE(__event->enabled)))                     \
                return;                                                       \
        __lf = lttng_rcu_dereference(__session->pid_tracker.p);               \
        if (__lf && likely(!lttng_id_tracker_lookup(__lf, current->tgid)))    \
@@ -1225,11 +1225,11 @@ static void __event_probe__##_name(void *__data)                              \
                                                                              \
        if (!_TP_SESSION_CHECK(session, __session))                           \
                return;                                                       \
-       if (unlikely(!READ_ONCE(__session->active)))                          \
+       if (unlikely(!LTTNG_READ_ONCE(__session->active)))                    \
                return;                                                       \
-       if (unlikely(!READ_ONCE(__chan->enabled)))                            \
+       if (unlikely(!LTTNG_READ_ONCE(__chan->enabled)))                      \
                return;                                                       \
-       if (unlikely(!READ_ONCE(__event->enabled)))                           \
+       if (unlikely(!LTTNG_READ_ONCE(__event->enabled)))                     \
                return;                                                       \
        __lf = lttng_rcu_dereference(__session->pid_tracker.p);               \
        if (__lf && likely(!lttng_id_tracker_lookup(__lf, current->tgid)))    \

diff --git a/probes/lttng-uprobes.c b/probes/lttng-uprobes.c
index bc1012895f958b48a1542443432ed7162b5bbbc7..bda1d9b46cbce41a5e4a06c2c3b3124e634fbfe3 100644 (file)
--- a/probes/lttng-uprobes.c
+++ b/probes/lttng-uprobes.c
@@ -40,11 +40,11 @@ int lttng_uprobes_handler_pre(struct uprobe_consumer *uc, struct pt_regs *regs)
                unsigned long ip;
        } payload;
 
-       if (unlikely(!READ_ONCE(chan->session->active)))
+       if (unlikely(!LTTNG_READ_ONCE(chan->session->active)))
                return 0;
-       if (unlikely(!READ_ONCE(chan->enabled)))
+       if (unlikely(!LTTNG_READ_ONCE(chan->enabled)))
                return 0;
-       if (unlikely(!READ_ONCE(event->enabled)))
+       if (unlikely(!LTTNG_READ_ONCE(event->enabled)))
                return 0;
 
        lib_ring_buffer_ctx_init(&ctx, chan->chan, &lttng_probe_ctx,

diff --git a/wrapper/compiler.h b/wrapper/compiler.h
index 1496f33e3807821fd19ac72e76e7bf35aacacd1f..b9f8c51861e7c20da983777eafde536a3f185312 100644 (file)
--- a/wrapper/compiler.h
+++ b/wrapper/compiler.h
@@ -9,6 +9,7 @@
 #define _LTTNG_WRAPPER_COMPILER_H
 
 #include <linux/compiler.h>
+#include <linux/version.h>
 
 /*
  * Don't allow compiling with buggy compiler.
@@ -39,4 +40,21 @@
 # define WRITE_ONCE(x, val)    ({ ACCESS_ONCE(x) = val; })
 #endif
 
+/*
+ * In v4.15 a smp read barrier was added to READ_ONCE to replace
+ * lockless_dereference(), replicate this behavior on prior kernels
+ * and remove calls to smp_read_barrier_depends which was dropped
+ * in v5.9.
+ */
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(4,15,0))
+#define LTTNG_READ_ONCE(x)     READ_ONCE(x)
+#else
+#define LTTNG_READ_ONCE(x)                     \
+({                                             \
+       typeof(x) __val = READ_ONCE(x);         \
+       smp_read_barrier_depends();             \
+       __val;                                  \
+})
+#endif
+
 #endif /* _LTTNG_WRAPPER_COMPILER_H */

diff --git a/wrapper/trace-clock.h b/wrapper/trace-clock.h
index 9f4e366afbcbeecc89302a2cb205b41b3e9012e5..187fc82b650d01a5d536724f92885c3bf24f9d47 100644 (file)
--- a/wrapper/trace-clock.h
+++ b/wrapper/trace-clock.h
@@ -160,33 +160,30 @@ static inline void put_trace_clock(void)
 
 static inline u64 trace_clock_read64(void)
 {
-       struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
+       struct lttng_trace_clock *ltc = LTTNG_READ_ONCE(lttng_trace_clock);
 
        if (likely(!ltc)) {
                return trace_clock_read64_monotonic();
        } else {
-               read_barrier_depends(); /* load ltc before content */
                return ltc->read64();
        }
 }
 
 static inline u64 trace_clock_freq(void)
 {
-       struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
+       struct lttng_trace_clock *ltc = LTTNG_READ_ONCE(lttng_trace_clock);
 
        if (!ltc) {
                return trace_clock_freq_monotonic();
        } else {
-               read_barrier_depends(); /* load ltc before content */
                return ltc->freq();
        }
 }
 
 static inline int trace_clock_uuid(char *uuid)
 {
-       struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
+       struct lttng_trace_clock *ltc = LTTNG_READ_ONCE(lttng_trace_clock);
 
-       read_barrier_depends(); /* load ltc before content */
        /* Use default UUID cb when NULL */
        if (!ltc || !ltc->uuid) {
                return trace_clock_uuid_monotonic(uuid);
@@ -197,24 +194,22 @@ static inline int trace_clock_uuid(char *uuid)
 
 static inline const char *trace_clock_name(void)
 {
-       struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
+       struct lttng_trace_clock *ltc = LTTNG_READ_ONCE(lttng_trace_clock);
 
        if (!ltc) {
                return trace_clock_name_monotonic();
        } else {
-               read_barrier_depends(); /* load ltc before content */
                return ltc->name();
        }
 }
 
 static inline const char *trace_clock_description(void)
 {
-       struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
+       struct lttng_trace_clock *ltc = LTTNG_READ_ONCE(lttng_trace_clock);
 
        if (!ltc) {
                return trace_clock_description_monotonic();
        } else {
-               read_barrier_depends(); /* load ltc before content */
                return ltc->description();
        }
 }