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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	stable@vger.kernel.org, Juergen Gross <jgross@suse.com>,
	David Woodhouse <dwmw@amazon.co.uk>,
	Salvatore Bonaccorso <carnil@debian.org>,
	Jason Andryuk <jandryuk@gmail.com>
Subject: [PATCH 4.19 15/37] xen: Fix XenStore initialisation for XS_LOCAL
Date: Tue,  2 Feb 2021 14:38:58 +0100	[thread overview]
Message-ID: <20210202132943.534336956@linuxfoundation.org> (raw)
In-Reply-To: <20210202132942.915040339@linuxfoundation.org>

From: David Woodhouse <dwmw@amazon.co.uk>

commit 5f46400f7a6a4fad635d5a79e2aa5a04a30ffea1 upstream.

In commit 3499ba8198ca ("xen: Fix event channel callback via INTX/GSI")
I reworked the triggering of xenbus_probe().

I tried to simplify things by taking out the workqueue based startup
triggered from wake_waiting(); the somewhat poorly named xenbus IRQ
handler.

I missed the fact that in the XS_LOCAL case (Dom0 starting its own
xenstored or xenstore-stubdom, which happens after the kernel is booted
completely), that IRQ-based trigger is still actually needed.

So... put it back, except more cleanly. By just spawning a xenbus_probe
thread which waits on xb_waitq and runs the probe the first time it
gets woken, just as the workqueue-based hack did.

This is actually a nicer approach for *all* the back ends with different
interrupt methods, and we can switch them all over to that without the
complex conditions for when to trigger it. But not in -rc6. This is
the minimal fix for the regression, although it's a step in the right
direction instead of doing a partial revert and actually putting the
workqueue back. It's also simpler than the workqueue.

Fixes: 3499ba8198ca ("xen: Fix event channel callback via INTX/GSI")
Reported-by: Juergen Gross <jgross@suse.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/4c9af052a6e0f6485d1de43f2c38b1461996db99.camel@infradead.org
Signed-off-by: Juergen Gross <jgross@suse.com>
Cc: Salvatore Bonaccorso <carnil@debian.org>
Cc: Jason Andryuk <jandryuk@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/xen/xenbus/xenbus_probe.c |   31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

--- a/drivers/xen/xenbus/xenbus_probe.c
+++ b/drivers/xen/xenbus/xenbus_probe.c
@@ -714,6 +714,23 @@ static bool xs_hvm_defer_init_for_callba
 #endif
 }
 
+static int xenbus_probe_thread(void *unused)
+{
+	DEFINE_WAIT(w);
+
+	/*
+	 * We actually just want to wait for *any* trigger of xb_waitq,
+	 * and run xenbus_probe() the moment it occurs.
+	 */
+	prepare_to_wait(&xb_waitq, &w, TASK_INTERRUPTIBLE);
+	schedule();
+	finish_wait(&xb_waitq, &w);
+
+	DPRINTK("probing");
+	xenbus_probe();
+	return 0;
+}
+
 static int __init xenbus_probe_initcall(void)
 {
 	/*
@@ -725,6 +742,20 @@ static int __init xenbus_probe_initcall(
 	     !xs_hvm_defer_init_for_callback()))
 		xenbus_probe();
 
+	/*
+	 * For XS_LOCAL, spawn a thread which will wait for xenstored
+	 * or a xenstore-stubdom to be started, then probe. It will be
+	 * triggered when communication starts happening, by waiting
+	 * on xb_waitq.
+	 */
+	if (xen_store_domain_type == XS_LOCAL) {
+		struct task_struct *probe_task;
+
+		probe_task = kthread_run(xenbus_probe_thread, NULL,
+					 "xenbus_probe");
+		if (IS_ERR(probe_task))
+			return PTR_ERR(probe_task);
+	}
 	return 0;
 }
 device_initcall(xenbus_probe_initcall);



  parent reply	other threads:[~2021-02-02 15:08 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-02 13:38 [PATCH 4.19 00/37] 4.19.173-rc1 review Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 01/37] nbd: freeze the queue while were adding connections Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 02/37] ACPI: sysfs: Prefer "compatible" modalias Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 03/37] kernel: kexec: remove the lock operation of system_transition_mutex Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 04/37] xen/privcmd: allow fetching resource sizes Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 05/37] ALSA: hda/via: Apply the workaround generically for Clevo machines Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 06/37] media: rc: ensure that uevent can be read directly after rc device register Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 07/37] ARM: dts: imx6qdl-gw52xx: fix duplicate regulator naming Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 08/37] wext: fix NULL-ptr-dereference with cfg80211s lack of commit() Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 09/37] net: usb: qmi_wwan: added support for Thales Cinterion PLSx3 modem family Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 10/37] PM: hibernate: flush swap writer after marking Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 11/37] drivers: soc: atmel: Avoid calling at91_soc_init on non AT91 SoCs Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 12/37] drivers: soc: atmel: add null entry at the end of at91_soc_allowed_list[] Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 13/37] KVM: x86/pmu: Fix HW_REF_CPU_CYCLES event pseudo-encoding in intel_arch_events[] Greg Kroah-Hartman
2021-02-02 13:38 ` [PATCH 4.19 14/37] KVM: x86: get smi pending status correctly Greg Kroah-Hartman
2021-02-02 13:38 ` Greg Kroah-Hartman [this message]
2021-02-02 13:38 ` [PATCH 4.19 16/37] leds: trigger: fix potential deadlock with libata Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 17/37] mt7601u: fix kernel crash unplugging the device Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 18/37] mt7601u: fix rx buffer refcounting Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 19/37] xen-blkfront: allow discard-* nodes to be optional Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 20/37] ARM: imx: build suspend-imx6.S with arm instruction set Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 21/37] netfilter: nft_dynset: add timeout extension to template Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 22/37] xfrm: Fix oops in xfrm_replay_advance_bmp Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 23/37] xfrm: fix disable_xfrm sysctl when used on xfrm interfaces Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 24/37] RDMA/cxgb4: Fix the reported max_recv_sge value Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 25/37] pNFS/NFSv4: Fix a layout segment leak in pnfs_layout_process() Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 26/37] iwlwifi: pcie: use jiffies for memory read spin time limit Greg Kroah-Hartman
2021-02-03 20:42   ` Pavel Machek
2021-02-02 13:39 ` [PATCH 4.19 27/37] iwlwifi: pcie: reschedule in long-running memory reads Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 28/37] mac80211: pause TX while changing interface type Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 29/37] net/mlx5: Fix memory leak on flow table creation error flow Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 30/37] can: dev: prevent potential information leak in can_fill_info() Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 31/37] iommu/vt-d: Gracefully handle DMAR units with no supported address widths Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 32/37] iommu/vt-d: Dont dereference iommu_device if IOMMU_API is not built Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 33/37] rxrpc: Fix memory leak in rxrpc_lookup_local Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 34/37] NFC: fix resource leak when target index is invalid Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 35/37] NFC: fix possible resource leak Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 36/37] team: protect features update by RCU to avoid deadlock Greg Kroah-Hartman
2021-02-02 13:39 ` [PATCH 4.19 37/37] tcp: fix TLP timer not set when CA_STATE changes from DISORDER to OPEN Greg Kroah-Hartman
2021-02-02 17:48 ` [PATCH 4.19 00/37] 4.19.173-rc1 review Pavel Machek
2021-02-02 20:21 ` Jon Hunter
2021-02-03  3:22 ` Naresh Kamboju
2021-02-03 15:42 ` Shuah Khan
2021-02-03 20:42 ` Guenter Roeck

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