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-rw-r--r--debian/patches-rt/0235-fs-namespace-Use-cpu_chill-in-trylock-loops.patch44
1 files changed, 44 insertions, 0 deletions
diff --git a/debian/patches-rt/0235-fs-namespace-Use-cpu_chill-in-trylock-loops.patch b/debian/patches-rt/0235-fs-namespace-Use-cpu_chill-in-trylock-loops.patch
new file mode 100644
index 000000000..046c48516
--- /dev/null
+++ b/debian/patches-rt/0235-fs-namespace-Use-cpu_chill-in-trylock-loops.patch
@@ -0,0 +1,44 @@
+From e174bc8c285602601d09d4e7997654e66a18bc87 Mon Sep 17 00:00:00 2001
+From: Thomas Gleixner <tglx@linutronix.de>
+Date: Wed, 7 Mar 2012 21:00:34 +0100
+Subject: [PATCH 235/323] fs: namespace: Use cpu_chill() in trylock loops
+Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.204-rt100.tar.xz
+
+Retry loops on RT might loop forever when the modifying side was
+preempted. Use cpu_chill() instead of cpu_relax() to let the system
+make progress.
+
+Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
+---
+ fs/namespace.c | 8 ++++++--
+ 1 file changed, 6 insertions(+), 2 deletions(-)
+
+diff --git a/fs/namespace.c b/fs/namespace.c
+index 046b084136c5..6a550e342d6b 100644
+--- a/fs/namespace.c
++++ b/fs/namespace.c
+@@ -14,6 +14,7 @@
+ #include <linux/mnt_namespace.h>
+ #include <linux/user_namespace.h>
+ #include <linux/namei.h>
++#include <linux/delay.h>
+ #include <linux/security.h>
+ #include <linux/cred.h>
+ #include <linux/idr.h>
+@@ -321,8 +322,11 @@ int __mnt_want_write(struct vfsmount *m)
+ * incremented count after it has set MNT_WRITE_HOLD.
+ */
+ smp_mb();
+- while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD)
+- cpu_relax();
++ while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) {
++ preempt_enable();
++ cpu_chill();
++ preempt_disable();
++ }
+ /*
+ * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
+ * be set to match its requirements. So we must not load that until
+--
+2.43.0
+