On Sun, May 13, 2018 at 08:15:37PM -0700, Joel Fernandes (Google) wrote: > The 'c' variable was used previously to store the grace period > that is being requested. However it is not very meaningful for > a code reader, this patch replaces it with gp_seq_start indicating that
Good catch, but how about "gp_seq_req" instead of gp_seq_start? Thanx, Paul > this is the grace period that was requested. Also updating tracing with > the new name. > > Just a clean up patch, no logical change. > > Signed-off-by: Joel Fernandes (Google) <j...@joelfernandes.org> > --- > include/trace/events/rcu.h | 15 ++++++------ > kernel/rcu/tree.c | 47 ++++++++++++++++++++++---------------- > 2 files changed, 35 insertions(+), 27 deletions(-) > > diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h > index ce9d1a1cac78..539900a9f8c7 100644 > --- a/include/trace/events/rcu.h > +++ b/include/trace/events/rcu.h > @@ -103,15 +103,16 @@ TRACE_EVENT(rcu_grace_period, > */ > TRACE_EVENT(rcu_future_grace_period, > > - TP_PROTO(const char *rcuname, unsigned long gp_seq, unsigned long c, > - u8 level, int grplo, int grphi, const char *gpevent), > + TP_PROTO(const char *rcuname, unsigned long gp_seq, > + unsigned long gp_seq_start, u8 level, int grplo, int grphi, > + const char *gpevent), > > - TP_ARGS(rcuname, gp_seq, c, level, grplo, grphi, gpevent), > + TP_ARGS(rcuname, gp_seq, gp_seq_start, level, grplo, grphi, gpevent), > > TP_STRUCT__entry( > __field(const char *, rcuname) > __field(unsigned long, gp_seq) > - __field(unsigned long, c) > + __field(unsigned long, gp_seq_start) > __field(u8, level) > __field(int, grplo) > __field(int, grphi) > @@ -121,7 +122,7 @@ TRACE_EVENT(rcu_future_grace_period, > TP_fast_assign( > __entry->rcuname = rcuname; > __entry->gp_seq = gp_seq; > - __entry->c = c; > + __entry->gp_seq_start = gp_seq_start; > __entry->level = level; > __entry->grplo = grplo; > __entry->grphi = grphi; > @@ -129,7 +130,7 @@ TRACE_EVENT(rcu_future_grace_period, > ), > > TP_printk("%s %lu %lu %u %d %d %s", > - __entry->rcuname, __entry->gp_seq, __entry->c, __entry->level, > + __entry->rcuname, __entry->gp_seq, __entry->gp_seq_start, > __entry->level, > __entry->grplo, __entry->grphi, __entry->gpevent) > ); > > @@ -751,7 +752,7 @@ TRACE_EVENT(rcu_barrier, > #else /* #ifdef CONFIG_RCU_TRACE */ > > #define trace_rcu_grace_period(rcuname, gp_seq, gpevent) do { } while (0) > -#define trace_rcu_future_grace_period(rcuname, gp_seq, c, \ > +#define trace_rcu_future_grace_period(rcuname, gp_seq, gp_seq_start, \ > level, grplo, grphi, event) \ > do { } while (0) > #define trace_rcu_grace_period_init(rcuname, gp_seq, level, grplo, grphi, \ > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index 29ccc60bdbfc..9f5679ba413b 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -1541,13 +1541,18 @@ void rcu_cpu_stall_reset(void) > > /* Trace-event wrapper function for trace_rcu_future_grace_period. */ > static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, > - unsigned long c, const char *s) > + unsigned long gp_seq_start, const char *s) > { > - trace_rcu_future_grace_period(rdp->rsp->name, rnp->gp_seq, c, > + trace_rcu_future_grace_period(rdp->rsp->name, rnp->gp_seq, gp_seq_start, > rnp->level, rnp->grplo, rnp->grphi, s); > } > > /* > + * rcu_start_this_gp - Request the start of a particular grace period > + * @rnp: The leaf node of the CPU from which to start. > + * @rdp: The rcu_data corresponding to the CPU from which to start. > + * @gp_seq_start: The gp_seq of the grace period to start. > + * > * Start the specified grace period, as needed to handle newly arrived > * callbacks. The required future grace periods are recorded in each > * rcu_node structure's ->gp_seq_needed field. Returns true if there > @@ -1555,9 +1560,11 @@ static void trace_rcu_this_gp(struct rcu_node *rnp, > struct rcu_data *rdp, > * > * The caller must hold the specified rcu_node structure's ->lock, which > * is why the caller is responsible for waking the grace-period kthread. > + * > + * Returns true if the GP thread needs to be awakened else false. > */ > static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, > - unsigned long c) > + unsigned long gp_seq_start) > { > bool ret = false; > struct rcu_state *rsp = rdp->rsp; > @@ -1573,18 +1580,19 @@ static bool rcu_start_this_gp(struct rcu_node *rnp, > struct rcu_data *rdp, > * not be released. > */ > raw_lockdep_assert_held_rcu_node(rnp); > - trace_rcu_this_gp(rnp, rdp, c, TPS("Startleaf")); > + trace_rcu_this_gp(rnp, rdp, gp_seq_start, TPS("Startleaf")); > for (rnp_root = rnp; 1; rnp_root = rnp_root->parent) { > if (rnp_root != rnp) > raw_spin_lock_rcu_node(rnp_root); > - if (ULONG_CMP_GE(rnp_root->gp_seq_needed, c) || > - rcu_seq_done(&rnp_root->gp_seq, c) || > + if (ULONG_CMP_GE(rnp_root->gp_seq_needed, gp_seq_start) || > + rcu_seq_done(&rnp_root->gp_seq, gp_seq_start) || > (rnp != rnp_root && > rcu_seq_state(rcu_seq_current(&rnp_root->gp_seq)))) { > - trace_rcu_this_gp(rnp_root, rdp, c, TPS("Prestarted")); > + trace_rcu_this_gp(rnp_root, rdp, gp_seq_start, > + TPS("Prestarted")); > goto unlock_out; > } > - rnp_root->gp_seq_needed = c; > + rnp_root->gp_seq_needed = gp_seq_start; > if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) > goto unlock_out; > if (rnp_root != rnp && rnp_root->parent != NULL) > @@ -1595,14 +1603,14 @@ static bool rcu_start_this_gp(struct rcu_node *rnp, > struct rcu_data *rdp, > > /* If GP already in progress, just leave, otherwise start one. */ > if (rcu_gp_in_progress(rsp)) { > - trace_rcu_this_gp(rnp_root, rdp, c, TPS("Startedleafroot")); > + trace_rcu_this_gp(rnp_root, rdp, gp_seq_start, > TPS("Startedleafroot")); > goto unlock_out; > } > - trace_rcu_this_gp(rnp_root, rdp, c, TPS("Startedroot")); > + trace_rcu_this_gp(rnp_root, rdp, gp_seq_start, TPS("Startedroot")); > WRITE_ONCE(rsp->gp_flags, rsp->gp_flags | RCU_GP_FLAG_INIT); > rsp->gp_req_activity = jiffies; > if (!rsp->gp_kthread) { > - trace_rcu_this_gp(rnp_root, rdp, c, TPS("NoGPkthread")); > + trace_rcu_this_gp(rnp_root, rdp, gp_seq_start, > TPS("NoGPkthread")); > goto unlock_out; > } > trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gp_seq), > TPS("newreq")); > @@ -1611,9 +1619,9 @@ static bool rcu_start_this_gp(struct rcu_node *rnp, > struct rcu_data *rdp, > if (rnp != rnp_root) > raw_spin_unlock_rcu_node(rnp_root); > /* Push furthest requested GP to leaf node and rcu_data structure. */ > - if (ULONG_CMP_GE(rnp_root->gp_seq_needed, c)) { > - rnp->gp_seq_needed = c; > - rdp->gp_seq_needed = c; > + if (ULONG_CMP_GE(rnp_root->gp_seq_needed, gp_seq_start)) { > + rnp->gp_seq_needed = gp_seq_start; > + rdp->gp_seq_needed = gp_seq_start; > } > return ret; > } > @@ -1624,14 +1632,13 @@ static bool rcu_start_this_gp(struct rcu_node *rnp, > struct rcu_data *rdp, > */ > static bool rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node > *rnp) > { > - unsigned long c = rnp->gp_seq; > bool needmore; > struct rcu_data *rdp = this_cpu_ptr(rsp->rda); > > needmore = ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed); > if (!needmore) > rnp->gp_seq_needed = rnp->gp_seq; /* Avoid counter wrap. */ > - trace_rcu_this_gp(rnp, rdp, c, > + trace_rcu_this_gp(rnp, rdp, rnp->gp_seq, > needmore ? TPS("CleanupMore") : TPS("Cleanup")); > return needmore; > } > @@ -1667,7 +1674,7 @@ static void rcu_gp_kthread_wake(struct rcu_state *rsp) > static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, > struct rcu_data *rdp) > { > - unsigned long c; > + unsigned long gp_seq_start; > bool ret = false; > > raw_lockdep_assert_held_rcu_node(rnp); > @@ -1686,9 +1693,9 @@ static bool rcu_accelerate_cbs(struct rcu_state *rsp, > struct rcu_node *rnp, > * accelerating callback invocation to an earlier grace-period > * number. > */ > - c = rcu_seq_snap(&rsp->gp_seq); > - if (rcu_segcblist_accelerate(&rdp->cblist, c)) > - ret = rcu_start_this_gp(rnp, rdp, c); > + gp_seq_start = rcu_seq_snap(&rsp->gp_seq); > + if (rcu_segcblist_accelerate(&rdp->cblist, gp_seq_start)) > + ret = rcu_start_this_gp(rnp, rdp, gp_seq_start); > > /* Trace depending on how much we were able to accelerate. */ > if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL)) > -- > 2.17.0.441.gb46fe60e1d-goog >