* [PATCH 1/1] rcu: Check for have_rcu_nocb_mask instead of rcu_nocb_mask @ 2014-07-17 21:30 Pranith Kumar 2014-07-17 23:49 ` Paul E. McKenney 0 siblings, 1 reply; 5+ messages in thread From: Pranith Kumar @ 2014-07-17 21:30 UTC (permalink / raw) To: Paul E. McKenney, Josh Triplett, Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, open list:READ-COPY UPDATE... Hi Paul, This is something similar to what you found yesterday with tick_nohz_full mask. -- Pranith If we configure a kernel with CONFIG_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_NONE=y and CONFIG_CPUMASK_OFFSTACK=n and do not pass in a rcu_nocb= boot parameter, the cpumask rcu_nocb_mask can be garbage instead of NULL. Hence this commit replaces checks for rcu_nocb_mask == NULL with a check for have_rcu_nocb_mask. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> --- kernel/rcu/tree_plugin.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index cedb020..15c00b5 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2542,7 +2542,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ struct rcu_data *rdp_prev = NULL; - if (rcu_nocb_mask == NULL) + if (!have_rcu_nocb_mask) return; #ifdef CONFIG_NO_HZ_FULL cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); @@ -2575,7 +2575,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ static bool init_nocb_callback_list(struct rcu_data *rdp) { - if (rcu_nocb_mask == NULL || + if (have_rcu_nocb_mask == false || !cpumask_test_cpu(rdp->cpu, rcu_nocb_mask)) return false; rdp->nxttail[RCU_NEXT_TAIL] = NULL; -- 1.9.1 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] rcu: Check for have_rcu_nocb_mask instead of rcu_nocb_mask 2014-07-17 21:30 [PATCH 1/1] rcu: Check for have_rcu_nocb_mask instead of rcu_nocb_mask Pranith Kumar @ 2014-07-17 23:49 ` Paul E. McKenney 2014-07-18 0:11 ` Pranith Kumar 0 siblings, 1 reply; 5+ messages in thread From: Paul E. McKenney @ 2014-07-17 23:49 UTC (permalink / raw) To: Pranith Kumar Cc: Josh Triplett, Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, open list:READ-COPY UPDATE... On Thu, Jul 17, 2014 at 05:30:11PM -0400, Pranith Kumar wrote: > Hi Paul, > > This is something similar to what you found yesterday with tick_nohz_full mask. > > -- > Pranith > > If we configure a kernel with CONFIG_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_NONE=y and > CONFIG_CPUMASK_OFFSTACK=n and do not pass in a rcu_nocb= boot parameter, the > cpumask rcu_nocb_mask can be garbage instead of NULL. > > Hence this commit replaces checks for rcu_nocb_mask == NULL with a check for > have_rcu_nocb_mask. > > Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> Good catch! Could you please forward-port this to current rcu/dev? This now includes the fix you mentioned above, which generates conflicts. Could you please also fix the use in rcu_is_nocb_cpu()? And please see the comment below. Thanx, Paul > --- > kernel/rcu/tree_plugin.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index cedb020..15c00b5 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -2542,7 +2542,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) > struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ > struct rcu_data *rdp_prev = NULL; > > - if (rcu_nocb_mask == NULL) > + if (!have_rcu_nocb_mask) > return; > #ifdef CONFIG_NO_HZ_FULL > cpumask_or(rcu_nocb_mask, rcu_nocb_mask, tick_nohz_full_mask); > @@ -2575,7 +2575,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) > /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ > static bool init_nocb_callback_list(struct rcu_data *rdp) > { > - if (rcu_nocb_mask == NULL || > + if (have_rcu_nocb_mask == false || This should really be "if (!have_rcu_nocb_mask". Of course, the original should have been "if (!rcu_nocb_mask", but old habits die hard. ;-) > !cpumask_test_cpu(rdp->cpu, rcu_nocb_mask)) > return false; > rdp->nxttail[RCU_NEXT_TAIL] = NULL; > -- > 1.9.1 > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] rcu: Check for have_rcu_nocb_mask instead of rcu_nocb_mask 2014-07-17 23:49 ` Paul E. McKenney @ 2014-07-18 0:11 ` Pranith Kumar 2014-07-19 6:10 ` Paul E. McKenney 0 siblings, 1 reply; 5+ messages in thread From: Pranith Kumar @ 2014-07-18 0:11 UTC (permalink / raw) To: paulmck Cc: Josh Triplett, Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, open list:READ-COPY UPDATE... On 07/17/2014 07:49 PM, Paul E. McKenney wrote: > On Thu, Jul 17, 2014 at 05:30:11PM -0400, Pranith Kumar wrote: >> Hi Paul, >> >> This is something similar to what you found yesterday with tick_nohz_full mask. >> >> -- >> Pranith >> >> If we configure a kernel with CONFIG_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_NONE=y and >> CONFIG_CPUMASK_OFFSTACK=n and do not pass in a rcu_nocb= boot parameter, the >> cpumask rcu_nocb_mask can be garbage instead of NULL. >> >> Hence this commit replaces checks for rcu_nocb_mask == NULL with a check for >> have_rcu_nocb_mask. >> >> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> > > Good catch! Could you please forward-port this to current rcu/dev? > This now includes the fix you mentioned above, which generates conflicts. > > Could you please also fix the use in rcu_is_nocb_cpu()? > > And please see the comment below. > Please find the fixed patch. -- Pranith From: Pranith Kumar <bobby.prani@gmail.com> Date: Thu, 17 Jul 2014 20:02:54 -0400 Subject: [PATCH 1/1] rcu: Feedback comments If we configure a kernel with CONFIG_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_NONE=y and CONFIG_CPUMASK_OFFSTACK=n and do not pass in a rcu_nocb= boot parameter, the cpumask rcu_nocb_mask can be garbage instead of NULL. Hence this commit replaces checks for rcu_nocb_mask == NULL with a check for have_rcu_nocb_mask. Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> --- kernel/rcu/tree_plugin.h | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index ce8c331..8f987c1 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2053,9 +2053,10 @@ static void rcu_init_one_nocb(struct rcu_node *rnp) /* Is the specified CPU a no-CBs CPU? */ bool rcu_is_nocb_cpu(int cpu) { - if (have_rcu_nocb_mask) - return cpumask_test_cpu(cpu, rcu_nocb_mask); - return false; + if (!have_rcu_nocb_mask) + return false; + + return cpumask_test_cpu(cpu, rcu_nocb_mask); } #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ @@ -2540,7 +2541,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ struct rcu_data *rdp_prev = NULL; - if (rcu_nocb_mask == NULL) + if (!have_rcu_nocb_mask) return; #if defined(CONFIG_NO_HZ_FULL) && !defined(CONFIG_NO_HZ_FULL_ALL) if (tick_nohz_full_running) @@ -2574,9 +2575,9 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ static bool init_nocb_callback_list(struct rcu_data *rdp) { - if (rcu_nocb_mask == NULL || - !cpumask_test_cpu(rdp->cpu, rcu_nocb_mask)) + if (!rcu_is_nocb_cpu(rdp->cpu)) return false; + rdp->nxttail[RCU_NEXT_TAIL] = NULL; return true; } -- 1.9.1 ^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] rcu: Check for have_rcu_nocb_mask instead of rcu_nocb_mask 2014-07-18 0:11 ` Pranith Kumar @ 2014-07-19 6:10 ` Paul E. McKenney 2014-07-19 6:32 ` Pranith Kumar 0 siblings, 1 reply; 5+ messages in thread From: Paul E. McKenney @ 2014-07-19 6:10 UTC (permalink / raw) To: Pranith Kumar Cc: Josh Triplett, Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, open list:READ-COPY UPDATE... On Thu, Jul 17, 2014 at 08:11:01PM -0400, Pranith Kumar wrote: > On 07/17/2014 07:49 PM, Paul E. McKenney wrote: > > On Thu, Jul 17, 2014 at 05:30:11PM -0400, Pranith Kumar wrote: > >> Hi Paul, > >> > >> This is something similar to what you found yesterday with tick_nohz_full mask. > >> > >> -- > >> Pranith > >> > >> If we configure a kernel with CONFIG_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_NONE=y and > >> CONFIG_CPUMASK_OFFSTACK=n and do not pass in a rcu_nocb= boot parameter, the > >> cpumask rcu_nocb_mask can be garbage instead of NULL. > >> > >> Hence this commit replaces checks for rcu_nocb_mask == NULL with a check for > >> have_rcu_nocb_mask. > >> > >> Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> > > > > Good catch! Could you please forward-port this to current rcu/dev? > > This now includes the fix you mentioned above, which generates conflicts. > > > > Could you please also fix the use in rcu_is_nocb_cpu()? > > > > And please see the comment below. > > > > Please find the fixed patch. > > -- > Pranith > > > From: Pranith Kumar <bobby.prani@gmail.com> > Date: Thu, 17 Jul 2014 20:02:54 -0400 > Subject: [PATCH 1/1] rcu: Feedback comments > > If we configure a kernel with CONFIG_NOCB_CPU=y, CONFIG_RCU_NOCB_CPU_NONE=y and > CONFIG_CPUMASK_OFFSTACK=n and do not pass in a rcu_nocb= boot parameter, the > cpumask rcu_nocb_mask can be garbage instead of NULL. > > Hence this commit replaces checks for rcu_nocb_mask == NULL with a check for > have_rcu_nocb_mask. > > Signed-off-by: Pranith Kumar <bobby.prani@gmail.com> > --- > kernel/rcu/tree_plugin.h | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > index ce8c331..8f987c1 100644 > --- a/kernel/rcu/tree_plugin.h > +++ b/kernel/rcu/tree_plugin.h > @@ -2053,9 +2053,10 @@ static void rcu_init_one_nocb(struct rcu_node *rnp) > /* Is the specified CPU a no-CBs CPU? */ > bool rcu_is_nocb_cpu(int cpu) > { > - if (have_rcu_nocb_mask) > - return cpumask_test_cpu(cpu, rcu_nocb_mask); > - return false; > + if (!have_rcu_nocb_mask) > + return false; > + > + return cpumask_test_cpu(cpu, rcu_nocb_mask); Hmmm... That was a subtle way to tell me that my feedback was bogus. ;-) I guess I need to stop reviewing patches at 2AM local time. Anyway, you are correct, this was OK to start with, so I am dropping this hunk. I queued the other two for 3.18. Thanx, Paul > } > #endif /* #ifndef CONFIG_RCU_NOCB_CPU_ALL */ > > @@ -2540,7 +2541,7 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) > struct rcu_data *rdp_leader = NULL; /* Suppress misguided gcc warn. */ > struct rcu_data *rdp_prev = NULL; > > - if (rcu_nocb_mask == NULL) > + if (!have_rcu_nocb_mask) > return; > #if defined(CONFIG_NO_HZ_FULL) && !defined(CONFIG_NO_HZ_FULL_ALL) > if (tick_nohz_full_running) > @@ -2574,9 +2575,9 @@ static void __init rcu_organize_nocb_kthreads(struct rcu_state *rsp) > /* Prevent __call_rcu() from enqueuing callbacks on no-CBs CPUs */ > static bool init_nocb_callback_list(struct rcu_data *rdp) > { > - if (rcu_nocb_mask == NULL || > - !cpumask_test_cpu(rdp->cpu, rcu_nocb_mask)) > + if (!rcu_is_nocb_cpu(rdp->cpu)) > return false; > + > rdp->nxttail[RCU_NEXT_TAIL] = NULL; > return true; > } > -- > 1.9.1 > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > ^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH 1/1] rcu: Check for have_rcu_nocb_mask instead of rcu_nocb_mask 2014-07-19 6:10 ` Paul E. McKenney @ 2014-07-19 6:32 ` Pranith Kumar 0 siblings, 0 replies; 5+ messages in thread From: Pranith Kumar @ 2014-07-19 6:32 UTC (permalink / raw) To: paulmck Cc: Josh Triplett, Steven Rostedt, Mathieu Desnoyers, Lai Jiangshan, open list:READ-COPY UPDATE... On 07/19/2014 02:10 AM, Paul E. McKenney wrote: >> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h >> index ce8c331..8f987c1 100644 >> --- a/kernel/rcu/tree_plugin.h >> +++ b/kernel/rcu/tree_plugin.h >> @@ -2053,9 +2053,10 @@ static void rcu_init_one_nocb(struct rcu_node *rnp) >> /* Is the specified CPU a no-CBs CPU? */ >> bool rcu_is_nocb_cpu(int cpu) >> { >> - if (have_rcu_nocb_mask) >> - return cpumask_test_cpu(cpu, rcu_nocb_mask); >> - return false; >> + if (!have_rcu_nocb_mask) >> + return false; >> + >> + return cpumask_test_cpu(cpu, rcu_nocb_mask); > > Hmmm... That was a subtle way to tell me that my feedback was bogus. ;-) > I guess I need to stop reviewing patches at 2AM local time. > > Anyway, you are correct, this was OK to start with, so I am dropping > this hunk. > I thought you wanted me to change the check of the have_rcu_nocb_mask, and I really think the new version is better. But yes, more of a style change :) -- Pranith ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2014-07-19 6:32 UTC | newest] Thread overview: 5+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2014-07-17 21:30 [PATCH 1/1] rcu: Check for have_rcu_nocb_mask instead of rcu_nocb_mask Pranith Kumar 2014-07-17 23:49 ` Paul E. McKenney 2014-07-18 0:11 ` Pranith Kumar 2014-07-19 6:10 ` Paul E. McKenney 2014-07-19 6:32 ` Pranith Kumar
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