From: Pavan Kondeti <pkondeti@codeaurora.org>
To: Frederic Weisbecker <frederic@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
"David S . Miller" <davem@davemloft.net>,
Linus Torvalds <torvalds@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
"Paul E . McKenney" <paulmck@linux.vnet.ibm.com>,
Ingo Molnar <mingo@kernel.org>,
Mauro Carvalho Chehab <mchehab@s-opensource.com>
Subject: Re: [RFC PATCH 29/30] softirq: Make softirq processing softinterruptible
Date: Tue, 16 Oct 2018 09:45:52 +0530 [thread overview]
Message-ID: <20181016041552.GA27587@codeaurora.org> (raw)
In-Reply-To: <1539213137-13953-30-git-send-email-frederic@kernel.org>
Hi Frederic,
On Thu, Oct 11, 2018 at 01:12:16AM +0200, Frederic Weisbecker wrote:
> From: Frederic Weisbecker <fweisbec@gmail.com>
>
> Make do_softirq() re-entrant and allow a vector, being either processed
> or disabled, to be interrupted by another vector. This way a vector
> won't be able to monopolize the CPU for a long while at the expense of
> the others that may rely on some predictable latency, especially on
> softirq disabled sections that used to disable all vectors.
>
I understand that a long running softirq can be preempted/interrupted by
other softirqs which is not possible today. I have few questions on your
patches.
(1) When softirq processing is pushed to ksoftirqd, then the long running
softirq can still block other softirqs (not in SOFTIRQ_NOW_MASK) for a while.
correct?
(2) When softirqs processing happens asynchronously, a particular softirq
like TASKLET can keep interrupting an already running softirq like TIMER/NET_RX,
correct? In worse case scenario, a long running softirq like NET_RX interrupt
a TIMER softirq. But I guess this is something expected with this. i.e
each softirq is independent and whichever comes recent gets to interrupt the
previously running softirqs.
Thanks,
Pavan
--
Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
next prev parent reply other threads:[~2018-10-16 4:16 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-10 23:11 [RFC PATCH 00/30] softirq: Make softirqs soft-interruptible (+ per vector disablement) Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 01/30] x86: Revert "x86/irq: Demote irq_cpustat_t::__softirq_pending to u16" Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 02/30] arch/softirq: Rename softirq_pending fields to softirq_data Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 03/30] softirq: Implement local_softirq_pending() below softirq vector definition Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 04/30] softirq: Normalize softirq_pending naming scheme Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 05/30] softirq: Convert softirq_pending_set() to softirq_pending_nand() Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 06/30] softirq: Introduce disabled softirq vectors bits Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 07/30] softirq: Rename _local_bh_enable() to local_bh_enable_no_softirq() Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 08/30] softirq: Move vectors bits to bottom_half.h Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 09/30] x86: Init softirq enabled field Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 10/30] softirq: Check enabled bits on the softirq loop Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 11/30] net: Prepare netif_tx_lock_bh/netif_tx_unlock_bh() for handling softirq mask Frederic Weisbecker
2018-10-10 23:11 ` [RFC PATCH 12/30] rcu: Prepare rcu_read_[un]lock_bh() " Frederic Weisbecker
2018-10-16 5:28 ` Joel Fernandes
2018-10-17 0:44 ` Frederic Weisbecker
2018-10-17 0:55 ` Joel Fernandes
2018-10-10 23:12 ` [RFC PATCH 13/30] net: Prepare tcp_get_md5sig_pool() " Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 14/30] softirq: Introduce local_bh_disable_all() Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 15/30] net: Prepare [un]lock_sock_fast() for handling softirq mask Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 16/30] net: Prepare nf_log_buf_open() " Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 17/30] isdn: Prepare isdn_net_get_locked_lp() " Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 18/30] softirq: Prepare local_bh_disable() " Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 19/30] diva: Prepare diva_os_enter_spin_lock() " Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 20/30] tg3: Prepare tg3_full_[un]lock() " Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 21/30] locking: Prepare spin_lock_bh() " Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 22/30] seqlock: Prepare write_seq[un]lock_bh() " Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 23/30] rwlock: Prepare write_[un]lock_bh() " Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 24/30] softirq: Introduce Local_bh_enter/exit() Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 25/30] softirq: Push down softirq mask to __local_bh_disable_ip() Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 26/30] softirq: Increment the softirq offset on top of enabled bits Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 27/30] softirq: Swap softirq serving VS disable on preempt mask layout Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 28/30] softirq: Disable vector on execution Frederic Weisbecker
2018-10-10 23:12 ` [RFC PATCH 29/30] softirq: Make softirq processing softinterruptible Frederic Weisbecker
2018-10-16 4:15 ` Pavan Kondeti [this message]
2018-10-17 0:26 ` Frederic Weisbecker
2018-10-22 8:12 ` Pavan Kondeti
2018-10-10 23:12 ` [RFC PATCH 30/30] softirq: Tasklet/net-rx fixup Frederic Weisbecker
2018-10-16 22:03 ` [RFC PATCH 00/30] softirq: Make softirqs soft-interruptible (+ per vector disablement) Jonathan Corbet
2018-10-16 23:37 ` Richard Cochran
2018-10-17 1:20 ` Frederic Weisbecker
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