* [for-next][PATCH 3/4] srcu: Fix warning to permit SRCU-fast readers in NMI handlers [not found] <20260130154607.755725833@kernel.org> @ 2026-01-30 15:46 ` Steven Rostedt 2026-01-30 15:51 ` Boqun Feng 0 siblings, 1 reply; 4+ messages in thread From: Steven Rostedt @ 2026-01-30 15:46 UTC (permalink / raw) To: linux-kernel Cc: Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Andrew Morton, Paul E. McKenney, Andrii Nakryiko, Boqun Feng, Alexei Starovoitov, Peter Zijlstra, bpf From: "Paul E. McKenney" <paulmck@kernel.org> SRCU-fast is designed to be used in NMI handlers, even going so far as to use atomic operations for architectures supporting NMIs but not providing NMI-safe per-CPU atomic operations. However, the WARN_ON_ONCE() in __srcu_check_read_flavor() complains if SRCU-fast is used in an NMI handler. This commit therefore modifies that WARN_ON_ONCE() to avoid such complaints. Reported-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Tested-by: Steven Rostedt <rostedt@goodmis.org> Cc: Andrii Nakryiko <andrii@kernel.org> Cc: Boqun Feng <boqun@kernel.org> Cc: Alexei Starovoitov <ast@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: bpf@vger.kernel.org Link: https://patch.msgid.link/8232efe8-a7a3-446c-af0b-19f9b523b4f7@paulmck-laptop Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> --- kernel/rcu/srcutree.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index ea3f128de06f..c4a0a93e8da4 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -789,7 +789,8 @@ void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) struct srcu_data *sdp; /* NMI-unsafe use in NMI is a bad sign, as is multi-bit read_flavor values. */ - WARN_ON_ONCE((read_flavor != SRCU_READ_FLAVOR_NMI) && in_nmi()); + WARN_ON_ONCE(read_flavor != SRCU_READ_FLAVOR_NMI && + read_flavor != SRCU_READ_FLAVOR_FAST && in_nmi()); WARN_ON_ONCE(read_flavor & (read_flavor - 1)); sdp = raw_cpu_ptr(ssp->sda); -- 2.51.0 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [for-next][PATCH 3/4] srcu: Fix warning to permit SRCU-fast readers in NMI handlers 2026-01-30 15:46 ` [for-next][PATCH 3/4] srcu: Fix warning to permit SRCU-fast readers in NMI handlers Steven Rostedt @ 2026-01-30 15:51 ` Boqun Feng 2026-01-30 17:17 ` Paul E. McKenney 2026-01-30 17:28 ` Steven Rostedt 0 siblings, 2 replies; 4+ messages in thread From: Boqun Feng @ 2026-01-30 15:51 UTC (permalink / raw) To: Steven Rostedt Cc: linux-kernel, Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Andrew Morton, Paul E. McKenney, Andrii Nakryiko, Alexei Starovoitov, Peter Zijlstra, bpf On Fri, Jan 30, 2026 at 10:46:10AM -0500, Steven Rostedt wrote: > From: "Paul E. McKenney" <paulmck@kernel.org> > > SRCU-fast is designed to be used in NMI handlers, even going so far > as to use atomic operations for architectures supporting NMIs but not > providing NMI-safe per-CPU atomic operations. However, the WARN_ON_ONCE() > in __srcu_check_read_flavor() complains if SRCU-fast is used in an NMI > handler. This commit therefore modifies that WARN_ON_ONCE() to avoid > such complaints. > > Reported-by: Steven Rostedt <rostedt@goodmis.org> > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > Tested-by: Steven Rostedt <rostedt@goodmis.org> > Cc: Andrii Nakryiko <andrii@kernel.org> > Cc: Boqun Feng <boqun@kernel.org> > Cc: Alexei Starovoitov <ast@kernel.org> > Cc: Peter Zijlstra <peterz@infradead.org> > Cc: bpf@vger.kernel.org > Link: https://patch.msgid.link/8232efe8-a7a3-446c-af0b-19f9b523b4f7@paulmck-laptop > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> Thank you, Steven! I will drop this in the RCU PR since you already plan to carry it via tracing. Regards, Boqun > --- > kernel/rcu/srcutree.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > index ea3f128de06f..c4a0a93e8da4 100644 > --- a/kernel/rcu/srcutree.c > +++ b/kernel/rcu/srcutree.c > @@ -789,7 +789,8 @@ void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) > struct srcu_data *sdp; > > /* NMI-unsafe use in NMI is a bad sign, as is multi-bit read_flavor values. */ > - WARN_ON_ONCE((read_flavor != SRCU_READ_FLAVOR_NMI) && in_nmi()); > + WARN_ON_ONCE(read_flavor != SRCU_READ_FLAVOR_NMI && > + read_flavor != SRCU_READ_FLAVOR_FAST && in_nmi()); > WARN_ON_ONCE(read_flavor & (read_flavor - 1)); > > sdp = raw_cpu_ptr(ssp->sda); > -- > 2.51.0 > > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [for-next][PATCH 3/4] srcu: Fix warning to permit SRCU-fast readers in NMI handlers 2026-01-30 15:51 ` Boqun Feng @ 2026-01-30 17:17 ` Paul E. McKenney 2026-01-30 17:28 ` Steven Rostedt 1 sibling, 0 replies; 4+ messages in thread From: Paul E. McKenney @ 2026-01-30 17:17 UTC (permalink / raw) To: Boqun Feng Cc: Steven Rostedt, linux-kernel, Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Andrew Morton, Andrii Nakryiko, Alexei Starovoitov, Peter Zijlstra, bpf On Fri, Jan 30, 2026 at 07:51:16AM -0800, Boqun Feng wrote: > On Fri, Jan 30, 2026 at 10:46:10AM -0500, Steven Rostedt wrote: > > From: "Paul E. McKenney" <paulmck@kernel.org> > > > > SRCU-fast is designed to be used in NMI handlers, even going so far > > as to use atomic operations for architectures supporting NMIs but not > > providing NMI-safe per-CPU atomic operations. However, the WARN_ON_ONCE() > > in __srcu_check_read_flavor() complains if SRCU-fast is used in an NMI > > handler. This commit therefore modifies that WARN_ON_ONCE() to avoid > > such complaints. > > > > Reported-by: Steven Rostedt <rostedt@goodmis.org> > > Signed-off-by: Paul E. McKenney <paulmck@kernel.org> > > Tested-by: Steven Rostedt <rostedt@goodmis.org> > > Cc: Andrii Nakryiko <andrii@kernel.org> > > Cc: Boqun Feng <boqun@kernel.org> > > Cc: Alexei Starovoitov <ast@kernel.org> > > Cc: Peter Zijlstra <peterz@infradead.org> > > Cc: bpf@vger.kernel.org > > Link: https://patch.msgid.link/8232efe8-a7a3-446c-af0b-19f9b523b4f7@paulmck-laptop > > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > > Thank you, Steven! I will drop this in the RCU PR since you already plan > to carry it via tracing. Thank you both! Thanx, Paul > Regards, > Boqun > > > --- > > kernel/rcu/srcutree.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c > > index ea3f128de06f..c4a0a93e8da4 100644 > > --- a/kernel/rcu/srcutree.c > > +++ b/kernel/rcu/srcutree.c > > @@ -789,7 +789,8 @@ void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) > > struct srcu_data *sdp; > > > > /* NMI-unsafe use in NMI is a bad sign, as is multi-bit read_flavor values. */ > > - WARN_ON_ONCE((read_flavor != SRCU_READ_FLAVOR_NMI) && in_nmi()); > > + WARN_ON_ONCE(read_flavor != SRCU_READ_FLAVOR_NMI && > > + read_flavor != SRCU_READ_FLAVOR_FAST && in_nmi()); > > WARN_ON_ONCE(read_flavor & (read_flavor - 1)); > > > > sdp = raw_cpu_ptr(ssp->sda); > > -- > > 2.51.0 > > > > ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [for-next][PATCH 3/4] srcu: Fix warning to permit SRCU-fast readers in NMI handlers 2026-01-30 15:51 ` Boqun Feng 2026-01-30 17:17 ` Paul E. McKenney @ 2026-01-30 17:28 ` Steven Rostedt 1 sibling, 0 replies; 4+ messages in thread From: Steven Rostedt @ 2026-01-30 17:28 UTC (permalink / raw) To: Boqun Feng Cc: linux-kernel, Masami Hiramatsu, Mark Rutland, Mathieu Desnoyers, Andrew Morton, Paul E. McKenney, Andrii Nakryiko, Alexei Starovoitov, Peter Zijlstra, bpf On Fri, 30 Jan 2026 07:51:16 -0800 Boqun Feng <boqun@kernel.org> wrote: > Thank you, Steven! I will drop this in the RCU PR since you already plan > to carry it via tracing. Thanks. It was a needed dependency for the last patch. -- Steve ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-01-30 17:28 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
[not found] <20260130154607.755725833@kernel.org>
2026-01-30 15:46 ` [for-next][PATCH 3/4] srcu: Fix warning to permit SRCU-fast readers in NMI handlers Steven Rostedt
2026-01-30 15:51 ` Boqun Feng
2026-01-30 17:17 ` Paul E. McKenney
2026-01-30 17:28 ` Steven Rostedt
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox