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Diffstat (limited to '')
| -rw-r--r-- | debian/patches-rt/0131-futex-Ensure-lock-unlock-symetry-versus-pi_lock-and-.patch | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/debian/patches-rt/0131-futex-Ensure-lock-unlock-symetry-versus-pi_lock-and-.patch b/debian/patches-rt/0131-futex-Ensure-lock-unlock-symetry-versus-pi_lock-and-.patch new file mode 100644 index 000000000..385cbe279 --- /dev/null +++ b/debian/patches-rt/0131-futex-Ensure-lock-unlock-symetry-versus-pi_lock-and-.patch @@ -0,0 +1,50 @@ +From be3ec67dc13250ace8bd04c65a4fb643d683c9c1 Mon Sep 17 00:00:00 2001 +From: Thomas Gleixner <tglx@linutronix.de> +Date: Fri, 1 Mar 2013 11:17:42 +0100 +Subject: [PATCH 131/347] futex: Ensure lock/unlock symetry versus pi_lock and + hash bucket lock +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.246-rt110.tar.xz + +In exit_pi_state_list() we have the following locking construct: + + spin_lock(&hb->lock); + raw_spin_lock_irq(&curr->pi_lock); + + ... + spin_unlock(&hb->lock); + +In !RT this works, but on RT the migrate_enable() function which is +called from spin_unlock() sees atomic context due to the held pi_lock +and just decrements the migrate_disable_atomic counter of the +task. Now the next call to migrate_disable() sees the counter being +negative and issues a warning. That check should be in +migrate_enable() already. + +Fix this by dropping pi_lock before unlocking hb->lock and reaquire +pi_lock after that again. This is safe as the loop code reevaluates +head again under the pi_lock. + +Reported-by: Yong Zhang <yong.zhang@windriver.com> +Signed-off-by: Thomas Gleixner <tglx@linutronix.de> +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + kernel/futex.c | 2 ++ + 1 file changed, 2 insertions(+) + +diff --git a/kernel/futex.c b/kernel/futex.c +index dc2d81d11b17..0e136045a720 100644 +--- a/kernel/futex.c ++++ b/kernel/futex.c +@@ -962,7 +962,9 @@ static void exit_pi_state_list(struct task_struct *curr) + if (head->next != next) { + /* retain curr->pi_lock for the loop invariant */ + raw_spin_unlock(&pi_state->pi_mutex.wait_lock); ++ raw_spin_unlock_irq(&curr->pi_lock); + spin_unlock(&hb->lock); ++ raw_spin_lock_irq(&curr->pi_lock); + put_pi_state(pi_state); + continue; + } +-- +2.36.1 + |