diff options
Diffstat (limited to 'patches/eventfd-Make-signal-recursion-protection-a-task-bit.patch')
| -rw-r--r-- | patches/eventfd-Make-signal-recursion-protection-a-task-bit.patch | 131 |
1 files changed, 0 insertions, 131 deletions
diff --git a/patches/eventfd-Make-signal-recursion-protection-a-task-bit.patch b/patches/eventfd-Make-signal-recursion-protection-a-task-bit.patch deleted file mode 100644 index 9734454fda38..000000000000 --- a/patches/eventfd-Make-signal-recursion-protection-a-task-bit.patch +++ /dev/null @@ -1,131 +0,0 @@ -From: Thomas Gleixner <tglx@linutronix.de> -Date: Thu, 29 Jul 2021 13:01:59 +0200 -Subject: [PATCH] eventfd: Make signal recursion protection a task bit - -The recursion protection for eventfd_signal() is based on a per CPU -variable and relies on the !RT semantics of spin_lock_irqsave() for -protecting this per CPU variable. On RT kernels spin_lock_irqsave() neither -disables preemption nor interrupts which allows the spin lock held section -to be preempted. If the preempting task invokes eventfd_signal() as well, -then the recursion warning triggers. - -Paolo suggested to protect the per CPU variable with a local lock, but -that's heavyweight and actually not necessary. The goal of this protection -is to prevent the task stack from overflowing, which can be achieved with a -per task recursion protection as well. - -Replace the per CPU variable with a per task bit similar to other recursion -protection bits like task_struct::in_page_owner. This works on both !RT and -RT kernels and removes as a side effect the extra per CPU storage. - -No functional change for !RT kernels. - -Reported-by: Daniel Bristot de Oliveira <bristot@redhat.com> -Signed-off-by: Thomas Gleixner <tglx@linutronix.de> -Tested-by: Daniel Bristot de Oliveira <bristot@redhat.com> -Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> ---- - fs/aio.c | 2 +- - fs/eventfd.c | 12 +++++------- - include/linux/eventfd.h | 11 +++++------ - include/linux/sched.h | 4 ++++ - 4 files changed, 15 insertions(+), 14 deletions(-) - ---- a/fs/aio.c -+++ b/fs/aio.c -@@ -1695,7 +1695,7 @@ static int aio_poll_wake(struct wait_que - list_del(&iocb->ki_list); - iocb->ki_res.res = mangle_poll(mask); - req->done = true; -- if (iocb->ki_eventfd && eventfd_signal_count()) { -+ if (iocb->ki_eventfd && eventfd_signal_allowed()) { - iocb = NULL; - INIT_WORK(&req->work, aio_poll_put_work); - schedule_work(&req->work); ---- a/fs/eventfd.c -+++ b/fs/eventfd.c -@@ -25,8 +25,6 @@ - #include <linux/idr.h> - #include <linux/uio.h> - --DEFINE_PER_CPU(int, eventfd_wake_count); -- - static DEFINE_IDA(eventfd_ida); - - struct eventfd_ctx { -@@ -67,21 +65,21 @@ struct eventfd_ctx { - * Deadlock or stack overflow issues can happen if we recurse here - * through waitqueue wakeup handlers. If the caller users potentially - * nested waitqueues with custom wakeup handlers, then it should -- * check eventfd_signal_count() before calling this function. If -- * it returns true, the eventfd_signal() call should be deferred to a -+ * check eventfd_signal_allowed() before calling this function. If -+ * it returns false, the eventfd_signal() call should be deferred to a - * safe context. - */ -- if (WARN_ON_ONCE(this_cpu_read(eventfd_wake_count))) -+ if (WARN_ON_ONCE(current->in_eventfd_signal)) - return 0; - - spin_lock_irqsave(&ctx->wqh.lock, flags); -- this_cpu_inc(eventfd_wake_count); -+ current->in_eventfd_signal = 1; - if (ULLONG_MAX - ctx->count < n) - n = ULLONG_MAX - ctx->count; - ctx->count += n; - if (waitqueue_active(&ctx->wqh)) - wake_up_locked_poll(&ctx->wqh, EPOLLIN); -- this_cpu_dec(eventfd_wake_count); -+ current->in_eventfd_signal = 0; - spin_unlock_irqrestore(&ctx->wqh.lock, flags); - - return n; ---- a/include/linux/eventfd.h -+++ b/include/linux/eventfd.h -@@ -14,6 +14,7 @@ - #include <linux/err.h> - #include <linux/percpu-defs.h> - #include <linux/percpu.h> -+#include <linux/sched.h> - - /* - * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining -@@ -43,11 +44,9 @@ int eventfd_ctx_remove_wait_queue(struct - __u64 *cnt); - void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt); - --DECLARE_PER_CPU(int, eventfd_wake_count); -- --static inline bool eventfd_signal_count(void) -+static inline bool eventfd_signal_allowed(void) - { -- return this_cpu_read(eventfd_wake_count); -+ return !current->in_eventfd_signal; - } - - #else /* CONFIG_EVENTFD */ -@@ -78,9 +77,9 @@ static inline int eventfd_ctx_remove_wai - return -ENOSYS; - } - --static inline bool eventfd_signal_count(void) -+static inline bool eventfd_signal_allowed(void) - { -- return false; -+ return true; - } - - static inline void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt) ---- a/include/linux/sched.h -+++ b/include/linux/sched.h -@@ -863,6 +863,10 @@ struct task_struct { - /* Used by page_owner=on to detect recursion in page tracking. */ - unsigned in_page_owner:1; - #endif -+#ifdef CONFIG_EVENTFD -+ /* Recursion prevention for eventfd_signal() */ -+ unsigned in_eventfd_signal:1; -+#endif - - unsigned long atomic_flags; /* Flags requiring atomic access. */ - |