I disagree. The 128-bit support is important because that's the lock-free timer implementation which was the whole idea. The lock-based code is just a work-around. We should rather add support in configure to detect compiler support for the -mcx16 flag which enables 128-bit CAS on x86-64. Now when I have an ARM64 target, I can actually write and test 128-bit CAS support on ARM (A64 ISA in AArch64 mode) and contribute that in another patch. I am not sure whether common compilers (e.g. GCC) properly supports 128-bit CAS on ARM64, might have to use LDXP/STXP (load/store exclusive pair) directly.
-- Ola On 16 May 2016 at 22:43, Bill Fischofer <[email protected]> wrote: > On Mon, May 16, 2016 at 2:15 PM, Maxim Uvarov <[email protected]> > wrote: > > > Remove totally untested branch with 128 bit optimizations > > for timer code. > > This also fixes static assert bug: > > https://bugs.linaro.org/show_bug.cgi?id=2211 > > > > Signed-off-by: Maxim Uvarov <[email protected]> > > > > Reviewed-and-tested-by: Bill Fischofer <[email protected]> > > > > --- > > platform/linux-generic/odp_timer.c | 107 > > ------------------------------------- > > 1 file changed, 107 deletions(-) > > > > diff --git a/platform/linux-generic/odp_timer.c > > b/platform/linux-generic/odp_timer.c > > index 6b84309..be28da3 100644 > > --- a/platform/linux-generic/odp_timer.c > > +++ b/platform/linux-generic/odp_timer.c > > @@ -11,15 +11,7 @@ > > * > > */ > > > > -/* Check if compiler supports 16-byte atomics. GCC needs -mcx16 flag on > > x86 */ > > -/* Using spin lock actually seems faster on Core2 */ > > -#ifdef ODP_ATOMIC_U128 > > -/* TB_NEEDS_PAD defined if sizeof(odp_buffer_t) != 8 */ > > -#define TB_NEEDS_PAD > > -#define TB_SET_PAD(x) ((x).pad = 0) > > -#else > > #define TB_SET_PAD(x) (void)(x) > > -#endif > > > > #include <odp_posix_extensions.h> > > > > @@ -70,11 +62,9 @@ > > * Mutual exclusion in the absence of CAS16 > > > > > *****************************************************************************/ > > > > -#ifndef ODP_ATOMIC_U128 > > #define NUM_LOCKS 1024 > > static _odp_atomic_flag_t locks[NUM_LOCKS]; /* Multiple locks per cache > > line! */ > > #define IDX2LOCK(idx) (&locks[(idx) % NUM_LOCKS]) > > -#endif > > > > > > > /****************************************************************************** > > * Translation between timeout buffer and timeout header > > @@ -98,17 +88,9 @@ static odp_timeout_hdr_t *timeout_hdr(odp_timeout_t > tmo) > > typedef struct tick_buf_s { > > odp_atomic_u64_t exp_tck;/* Expiration tick or TMO_xxx */ > > odp_buffer_t tmo_buf;/* ODP_BUFFER_INVALID if timer not active */ > > -#ifdef TB_NEEDS_PAD > > - uint32_t pad;/* Need to be able to access padding for successful > > CAS */ > > -#endif > > } tick_buf_t > > -#ifdef ODP_ATOMIC_U128 > > -ODP_ALIGNED(16) /* 16-byte atomic operations need properly aligned > > addresses */ > > -#endif > > ; > > > > -ODP_STATIC_ASSERT(sizeof(tick_buf_t) == 16, "sizeof(tick_buf_t) == 16"); > > - > > typedef struct odp_timer_s { > > void *user_ptr; > > odp_queue_t queue;/* Used for free list when timer is free */ > > @@ -378,34 +360,6 @@ static bool timer_reset(uint32_t idx, > > tick_buf_t *tb = &tp->tick_buf[idx]; > > > > if (tmo_buf == NULL || *tmo_buf == ODP_BUFFER_INVALID) { > > -#ifdef ODP_ATOMIC_U128 > > - tick_buf_t new, old; > > - do { > > - /* Relaxed and non-atomic read of current values > */ > > - old.exp_tck.v = tb->exp_tck.v; > > - old.tmo_buf = tb->tmo_buf; > > - TB_SET_PAD(old); > > - /* Check if there actually is a timeout buffer > > - * present */ > > - if (old.tmo_buf == ODP_BUFFER_INVALID) { > > - /* Cannot reset a timer with neither old > > nor > > - * new timeout buffer */ > > - success = false; > > - break; > > - } > > - /* Set up new values */ > > - new.exp_tck.v = abs_tck; > > - new.tmo_buf = old.tmo_buf; > > - TB_SET_PAD(new); > > - /* Atomic CAS will fail if we experienced torn > > reads, > > - * retry update sequence until CAS succeeds */ > > - } while (!_odp_atomic_u128_cmp_xchg_mm( > > - (_odp_atomic_u128_t *)tb, > > - (_uint128_t *)&old, > > - (_uint128_t *)&new, > > - _ODP_MEMMODEL_RLS, > > - _ODP_MEMMODEL_RLX)); > > -#else > > #ifdef __ARM_ARCH > > /* Since barriers are not good for C-A15, we take an > > * alternative approach using relaxed memory model */ > > @@ -453,7 +407,6 @@ static bool timer_reset(uint32_t idx, > > /* Release the lock */ > > _odp_atomic_flag_clear(IDX2LOCK(idx)); > > #endif > > -#endif > > } else { > > /* We have a new timeout buffer which replaces any old > one > > */ > > /* Fill in some (constant) header fields for timeout > > events */ > > @@ -468,19 +421,6 @@ static bool timer_reset(uint32_t idx, > > } > > /* Else ignore buffers of other types */ > > odp_buffer_t old_buf = ODP_BUFFER_INVALID; > > -#ifdef ODP_ATOMIC_U128 > > - tick_buf_t new, old; > > - new.exp_tck.v = abs_tck; > > - new.tmo_buf = *tmo_buf; > > - TB_SET_PAD(new); > > - /* We are releasing the new timeout buffer to some other > > - * thread */ > > - _odp_atomic_u128_xchg_mm((_odp_atomic_u128_t *)tb, > > - (_uint128_t *)&new, > > - (_uint128_t *)&old, > > - _ODP_MEMMODEL_ACQ_RLS); > > - old_buf = old.tmo_buf; > > -#else > > /* Take a related lock */ > > while (_odp_atomic_flag_tas(IDX2LOCK(idx))) > > /* While lock is taken, spin using relaxed loads > */ > > @@ -496,7 +436,6 @@ static bool timer_reset(uint32_t idx, > > > > /* Release the lock */ > > _odp_atomic_flag_clear(IDX2LOCK(idx)); > > -#endif > > /* Return old timeout buffer */ > > *tmo_buf = old_buf; > > } > > @@ -510,18 +449,6 @@ static odp_buffer_t timer_cancel(odp_timer_pool *tp, > > tick_buf_t *tb = &tp->tick_buf[idx]; > > odp_buffer_t old_buf; > > > > -#ifdef ODP_ATOMIC_U128 > > - tick_buf_t new, old; > > - /* Update the timer state (e.g. cancel the current timeout) */ > > - new.exp_tck.v = new_state; > > - /* Swap out the old buffer */ > > - new.tmo_buf = ODP_BUFFER_INVALID; > > - TB_SET_PAD(new); > > - _odp_atomic_u128_xchg_mm((_odp_atomic_u128_t *)tb, > > - (_uint128_t *)&new, (_uint128_t *)&old, > > - _ODP_MEMMODEL_RLX); > > - old_buf = old.tmo_buf; > > -#else > > /* Take a related lock */ > > while (_odp_atomic_flag_tas(IDX2LOCK(idx))) > > /* While lock is taken, spin using relaxed loads */ > > @@ -537,7 +464,6 @@ static odp_buffer_t timer_cancel(odp_timer_pool *tp, > > > > /* Release the lock */ > > _odp_atomic_flag_clear(IDX2LOCK(idx)); > > -#endif > > /* Return the old buffer */ > > return old_buf; > > } > > @@ -548,34 +474,6 @@ static unsigned timer_expire(odp_timer_pool *tp, > > uint32_t idx, uint64_t tick) > > tick_buf_t *tb = &tp->tick_buf[idx]; > > odp_buffer_t tmo_buf = ODP_BUFFER_INVALID; > > uint64_t exp_tck; > > -#ifdef ODP_ATOMIC_U128 > > - /* Atomic re-read for correctness */ > > - exp_tck = _odp_atomic_u64_load_mm(&tb->exp_tck, > _ODP_MEMMODEL_RLX); > > - /* Re-check exp_tck */ > > - if (odp_likely(exp_tck <= tick)) { > > - /* Attempt to grab timeout buffer, replace with inactive > > timer > > - * and invalid buffer */ > > - tick_buf_t new, old; > > - old.exp_tck.v = exp_tck; > > - old.tmo_buf = tb->tmo_buf; > > - TB_SET_PAD(old); > > - /* Set the inactive/expired bit keeping the expiration > > tick so > > - * that we can check against the expiration tick of the > > timeout > > - * when it is received */ > > - new.exp_tck.v = exp_tck | TMO_INACTIVE; > > - new.tmo_buf = ODP_BUFFER_INVALID; > > - TB_SET_PAD(new); > > - int succ = _odp_atomic_u128_cmp_xchg_mm( > > - (_odp_atomic_u128_t *)tb, > > - (_uint128_t *)&old, (_uint128_t *)&new, > > - _ODP_MEMMODEL_RLS, _ODP_MEMMODEL_RLX); > > - if (succ) > > - tmo_buf = old.tmo_buf; > > - /* Else CAS failed, something changed => skip timer > > - * this tick, it will be checked again next tick */ > > - } > > - /* Else false positive, ignore */ > > -#else > > /* Take a related lock */ > > while (_odp_atomic_flag_tas(IDX2LOCK(idx))) > > /* While lock is taken, spin using relaxed loads */ > > @@ -600,7 +498,6 @@ static unsigned timer_expire(odp_timer_pool *tp, > > uint32_t idx, uint64_t tick) > > /* Else false positive, ignore */ > > /* Release the lock */ > > _odp_atomic_flag_clear(IDX2LOCK(idx)); > > -#endif > > if (odp_likely(tmo_buf != ODP_BUFFER_INVALID)) { > > /* Fill in expiration tick for timeout events */ > > if (odp_event_type(odp_buffer_to_event(tmo_buf)) == > > @@ -974,13 +871,9 @@ void odp_timeout_free(odp_timeout_t tmo) > > > > int odp_timer_init_global(void) > > { > > -#ifndef ODP_ATOMIC_U128 > > uint32_t i; > > for (i = 0; i < NUM_LOCKS; i++) > > _odp_atomic_flag_clear(&locks[i]); > > -#else > > - ODP_DBG("Using lock-less timer implementation\n"); > > -#endif > > odp_atomic_init_u32(&num_timer_pools, 0); > > > > block_sigalarm(); > > -- > > 2.7.1.250.gff4ea60 > > > > _______________________________________________ > > lng-odp mailing list > > [email protected] > > https://lists.linaro.org/mailman/listinfo/lng-odp > > > _______________________________________________ > lng-odp mailing list > [email protected] > https://lists.linaro.org/mailman/listinfo/lng-odp > _______________________________________________ lng-odp mailing list [email protected] https://lists.linaro.org/mailman/listinfo/lng-odp
