6.6-stable review patch. If anyone has any objections, please let me know.
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From: Peter Zijlstra peterz@infradead.org
[ Upstream commit ef1ea98c8fffe227e5319215d84a53fa2a4bcebc ]
__schedule() // disable irqs <NMI> task_work_add(current, work, TWA_NMI_CURRENT); </NMI> // current = next; // enable irqs <IRQ> task_work_set_notify_irq() test_and_set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); // wrong task! </IRQ> // original task skips task work on its next return to user (or exit!)
Fixes: 466e4d801cd4 ("task_work: Add TWA_NMI_CURRENT as an additional notify mode.") Reported-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Steven Rostedt (Google) rostedt@goodmis.org Link: https://patch.msgid.link/20250924080118.425949403@infradead.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/task_work.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/kernel/task_work.c b/kernel/task_work.c index c969f1f26be58..48ab6275e6e7e 100644 --- a/kernel/task_work.c +++ b/kernel/task_work.c @@ -9,7 +9,12 @@ static struct callback_head work_exited; /* all we need is ->next == NULL */ #ifdef CONFIG_IRQ_WORK static void task_work_set_notify_irq(struct irq_work *entry) { - test_and_set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); + /* + * no-op IPI + * + * TWA_NMI_CURRENT will already have set the TIF flag, all + * this interrupt does it tickle the return-to-user path. + */ } static DEFINE_PER_CPU(struct irq_work, irq_work_NMI_resume) = IRQ_WORK_INIT_HARD(task_work_set_notify_irq); @@ -98,6 +103,7 @@ int task_work_add(struct task_struct *task, struct callback_head *work, break; #ifdef CONFIG_IRQ_WORK case TWA_NMI_CURRENT: + set_tsk_thread_flag(current, TIF_NOTIFY_RESUME); irq_work_queue(this_cpu_ptr(&irq_work_NMI_resume)); break; #endif