@@ -80,21 +80,6 @@ static void wakeup_softirqd(void)
wake_up_process(tsk);
}
-/*
- * If ksoftirqd is scheduled, we do not want to process pending softirqs
- * right now. Let ksoftirqd handle this at its own rate, to get fairness,
- * unless we're doing some of the synchronous softirqs.
- */
-#define SOFTIRQ_NOW_MASK ((1 << HI_SOFTIRQ) | (1 << TASKLET_SOFTIRQ))
-static bool ksoftirqd_running(unsigned long pending)
-{
- struct task_struct *tsk = __this_cpu_read(ksoftirqd);
-
- if (pending & SOFTIRQ_NOW_MASK)
- return false;
- return tsk && task_is_running(tsk) && !__kthread_should_park(tsk);
-}
-
#ifdef CONFIG_TRACE_IRQFLAGS
DEFINE_PER_CPU(int, hardirqs_enabled);
DEFINE_PER_CPU(int, hardirq_context);
@@ -236,7 +221,7 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int cnt)
goto out;
pending = local_softirq_pending();
- if (!pending || ksoftirqd_running(pending))
+ if (!pending)
goto out;
/*
@@ -432,9 +417,6 @@ static inline bool should_wake_ksoftirqd(void)
static inline void invoke_softirq(void)
{
- if (ksoftirqd_running(local_softirq_pending()))
- return;
-
if (!force_irqthreads() || !__this_cpu_read(ksoftirqd)) {
#ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
/*
@@ -468,7 +450,7 @@ asmlinkage __visible void do_softirq(void)
pending = local_softirq_pending();
- if (pending && !ksoftirqd_running(pending))
+ if (pending)
do_softirq_own_stack();
local_irq_restore(flags);
The following commit has been merged into the irq/core branch of tip: Commit-ID: d15121be7485655129101f3960ae6add40204463 Gitweb: https://git.kernel.org/tip/d15121be7485655129101f3960ae6add40204463 Author: Paolo Abeni <pabeni@redhat.com> AuthorDate: Mon, 08 May 2023 08:17:44 +02:00 Committer: Thomas Gleixner <tglx@linutronix.de> CommitterDate: Tue, 09 May 2023 21:50:27 +02:00 Revert "softirq: Let ksoftirqd do its job" This reverts the following commits: 4cd13c21b207 ("softirq: Let ksoftirqd do its job") 3c53776e29f8 ("Mark HI and TASKLET softirq synchronous") 1342d8080f61 ("softirq: Don't skip softirq execution when softirq thread is parking") in a single change to avoid known bad intermediate states introduced by a patch series reverting them individually. Due to the mentioned commit, when the ksoftirqd threads take charge of softirq processing, the system can experience high latencies. In the past a few workarounds have been implemented for specific side-effects of the initial ksoftirqd enforcement commit: commit 1ff688209e2e ("watchdog: core: make sure the watchdog_worker is not deferred") commit 8d5755b3f77b ("watchdog: softdog: fire watchdog even if softirqs do not get to run") commit 217f69743681 ("net: busy-poll: allow preemption in sk_busy_loop()") commit 3c53776e29f8 ("Mark HI and TASKLET softirq synchronous") But the latency problem still exists in real-life workloads, see the link below. The reverted commit intended to solve a live-lock scenario that can now be addressed with the NAPI threaded mode, introduced with commit 29863d41bb6e ("net: implement threaded-able napi poll loop support"), which is nowadays in a pretty stable status. While a complete solution to put softirq processing under nice resource control would be preferable, that has proven to be a very hard task. In the short term, remove the main pain point, and also simplify a bit the current softirq implementation. Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Jason Xing <kerneljasonxing@gmail.com> Reviewed-by: Jakub Kicinski <kuba@kernel.org> Reviewed-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Cc: "Paul E. McKenney" <paulmck@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: netdev@vger.kernel.org Link: https://lore.kernel.org/netdev/305d7742212cbe98621b16be782b0562f1012cb6.camel@redhat.com Link: https://lore.kernel.org/r/57e66b364f1b6f09c9bc0316742c3b14f4ce83bd.1683526542.git.pabeni@redhat.com --- kernel/softirq.c | 22 ++-------------------- 1 file changed, 2 insertions(+), 20 deletions(-)