[v6] rseq: Optimize exit to user space

[patch V6 21/31] rseq: Make exit debugging static branch based

Posted by Thomas Gleixner 1 month, 3 weeks ago

Disconnect it from the config switch and use the static debug branch. This
is a temporary measure for validating the rework. At the end this check
needs to be hidden behind lockdep as it has nothing to do with the other
debug infrastructure, which mainly aids user space debugging by enabling a
zoo of checks which terminate misbehaving tasks instead of letting them
keep the hard to diagnose pieces.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

---
 include/linux/rseq_entry.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/include/linux/rseq_entry.h
+++ b/include/linux/rseq_entry.h
@@ -285,7 +285,7 @@ static __always_inline void rseq_exit_to
 
 	rseq_stat_inc(rseq_stats.exit);
 
-	if (IS_ENABLED(CONFIG_DEBUG_RSEQ))
+	if (static_branch_unlikely(&rseq_debug_enabled))
 		WARN_ON_ONCE(ev->sched_switch);
 
 	/*

[tip: core/rseq] rseq: Make exit debugging static branch based

Posted by tip-bot2 for Thomas Gleixner 1 month, 1 week ago

The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     c1cbad8f99b5c73c6af6e96acbfa64eaaaeb085f
Gitweb:        https://git.kernel.org/tip/c1cbad8f99b5c73c6af6e96acbfa64eaaaeb085f
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:45:02 +01:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Tue, 04 Nov 2025 08:33:20 +01:00

rseq: Make exit debugging static branch based

Disconnect it from the config switch and use the static debug branch. This
is a temporary measure for validating the rework. At the end this check
needs to be hidden behind lockdep as it has nothing to do with the other
debug infrastructure, which mainly aids user space debugging by enabling a
zoo of checks which terminate misbehaving tasks instead of letting them
keep the hard to diagnose pieces.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251027084307.272660745@linutronix.de
---
 include/linux/rseq_entry.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/rseq_entry.h b/include/linux/rseq_entry.h
index f9510ce..5bdcf5b 100644
--- a/include/linux/rseq_entry.h
+++ b/include/linux/rseq_entry.h
@@ -285,7 +285,7 @@ static __always_inline void rseq_exit_to_user_mode(void)
 
 	rseq_stat_inc(rseq_stats.exit);
 
-	if (IS_ENABLED(CONFIG_DEBUG_RSEQ))
+	if (static_branch_unlikely(&rseq_debug_enabled))
 		WARN_ON_ONCE(ev->sched_switch);
 
 	/*

[tip: core/rseq] rseq: Make exit debugging static branch based

Posted by tip-bot2 for Thomas Gleixner 1 month, 2 weeks ago

The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     10ad7e96d88c286e018c4507add219bbef55bfcf
Gitweb:        https://git.kernel.org/tip/10ad7e96d88c286e018c4507add219bbef55bfcf
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:45:02 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 03 Nov 2025 15:26:19 +01:00

rseq: Make exit debugging static branch based

Disconnect it from the config switch and use the static debug branch. This
is a temporary measure for validating the rework. At the end this check
needs to be hidden behind lockdep as it has nothing to do with the other
debug infrastructure, which mainly aids user space debugging by enabling a
zoo of checks which terminate misbehaving tasks instead of letting them
keep the hard to diagnose pieces.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251027084307.272660745@linutronix.de
---
 include/linux/rseq_entry.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/rseq_entry.h b/include/linux/rseq_entry.h
index f9510ce..5bdcf5b 100644
--- a/include/linux/rseq_entry.h
+++ b/include/linux/rseq_entry.h
@@ -285,7 +285,7 @@ static __always_inline void rseq_exit_to_user_mode(void)
 
 	rseq_stat_inc(rseq_stats.exit);
 
-	if (IS_ENABLED(CONFIG_DEBUG_RSEQ))
+	if (static_branch_unlikely(&rseq_debug_enabled))
 		WARN_ON_ONCE(ev->sched_switch);
 
 	/*

[tip: core/rseq] rseq: Make exit debugging static branch based

Posted by tip-bot2 for Thomas Gleixner 1 month, 2 weeks ago

The following commit has been merged into the core/rseq branch of tip:

Commit-ID:     0042fe6474333f3e29984054fe4b3b56d1611847
Gitweb:        https://git.kernel.org/tip/0042fe6474333f3e29984054fe4b3b56d1611847
Author:        Thomas Gleixner <tglx@linutronix.de>
AuthorDate:    Mon, 27 Oct 2025 09:45:02 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Wed, 29 Oct 2025 11:07:17 +01:00

rseq: Make exit debugging static branch based

Disconnect it from the config switch and use the static debug branch. This
is a temporary measure for validating the rework. At the end this check
needs to be hidden behind lockdep as it has nothing to do with the other
debug infrastructure, which mainly aids user space debugging by enabling a
zoo of checks which terminate misbehaving tasks instead of letting them
keep the hard to diagnose pieces.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://patch.msgid.link/20251027084307.272660745@linutronix.de
---
 include/linux/rseq_entry.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/rseq_entry.h b/include/linux/rseq_entry.h
index f9510ce..5bdcf5b 100644
--- a/include/linux/rseq_entry.h
+++ b/include/linux/rseq_entry.h
@@ -285,7 +285,7 @@ static __always_inline void rseq_exit_to_user_mode(void)
 
 	rseq_stat_inc(rseq_stats.exit);
 
-	if (IS_ENABLED(CONFIG_DEBUG_RSEQ))
+	if (static_branch_unlikely(&rseq_debug_enabled))
 		WARN_ON_ONCE(ev->sched_switch);
 
 	/*