linux-kernel - [RFC PATCH 0/3] chelsio: cxgb: Use threaded irqs

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Message-Id: <20201224131148.300691-1-a.darwish@linutronix.de>
Date:   Thu, 24 Dec 2020 14:11:45 +0100
From:   "Ahmed S. Darwish" <a.darwish@...utronix.de>
To:     Rahul Lakkireddy <rahul.lakkireddy@...lsio.com>,
        Rohit Maheshwari <rohitm@...lsio.com>,
        Vinay Kumar Yadav <vinay.yadav@...lsio.com>,
        Vishal Kulkarni <vishal@...lsio.com>, netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Sebastian A. Siewior" <bigeasy@...utronix.de>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>
Subject: [RFC PATCH 0/3] chelsio: cxgb: Use threaded irqs

Folks,

The t1_interrupt() irq handler calls del_timer_sync() down the chain:

   sge.c: t1_interrupt()
     -> subr.c: t1_slow_intr_handler()
       -> asic_slow_intr() || fpga_slow_intr()
         -> t1_pci_intr_handler()
 	  -> cxgb2.c: t1_fatal_err()		# Cont. at [*]
       -> fpga_slow_intr()
         -> sge.c: t1_sge_intr_error_handler()
 	  -> cxgb2.c: t1_fatal_err()		# Cont. at [*]

[*] cxgb2.c: t1_fatal_err()
      -> sge.c: t1_sge_stop()
        -> timer.c: del_timer_sync()

This is invalid: if an irq handler calls del_timer_sync() on a timer
it has already interrupted, it will just loop forever.  That's why
del_timer_sync() also has a WARN_ON(in_irq()).

Included is an RFC patch series that runs the interrupt handler slow
path, t1_slow_intr_handler(), in a threaded-irq context.

This also leads to nice code savings across the driver, as some
workqueues and spinlocks are no longer needed.

Note: Only compile-tested. I do not have the hardware in question.

Thanks,

8<--------------

Ahmed S. Darwish (3):
  chelsio: cxgb: Remove ndo_poll_controller()
  chelsio: cxgb: Move slow interrupt handling to threaded irqs
  chelsio: cxgb: Do not schedule a workqueue for external interrupts

 drivers/net/ethernet/chelsio/cxgb/common.h |  2 -
 drivers/net/ethernet/chelsio/cxgb/cxgb2.c  | 58 ++--------------------
 drivers/net/ethernet/chelsio/cxgb/sge.c    | 25 +++++++---
 drivers/net/ethernet/chelsio/cxgb/sge.h    |  3 +-
 drivers/net/ethernet/chelsio/cxgb/subr.c   |  2 +-
 5 files changed, 25 insertions(+), 65 deletions(-)

base-commit: 2c85ebc57b3e1817b6ce1a6b703928e113a90442
-- 
2.29.2