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[PATCH 3.12 09/39] ring-buffer: Always run per-cpu ring buffer resize with schedule_work_on()

From Jiri Slaby <jslaby@suse.cz>
Newsgroups linux.kernel
Subject [PATCH 3.12 09/39] ring-buffer: Always run per-cpu ring buffer resize with schedule_work_on()
Date 2016-01-25 13:10 +0100
Message-ID <qUO82-3Gp-31@gated-at.bofh.it> (permalink)
References <qUNYl-3kJ-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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From: Corey Minyard <cminyard@mvista.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 021c5b34452d52e51664f09b98cd50c5495e74b6 upstream.

The code for resizing the trace ring buffers has to run the per-cpu
resize on the CPU itself.  The code was using preempt_off() and
running the code for the current CPU directly, otherwise calling
schedule_work_on().

At least on RT this could result in the following:

|BUG: sleeping function called from invalid context at kernel/rtmutex.c:673
|in_atomic(): 1, irqs_disabled(): 0, pid: 607, name: bash
|3 locks held by bash/607:
|CPU: 0 PID: 607 Comm: bash Not tainted 3.12.15-rt25+ #124
|(rt_spin_lock+0x28/0x68)
|(free_hot_cold_page+0x84/0x3b8)
|(free_buffer_page+0x14/0x20)
|(rb_update_pages+0x280/0x338)
|(ring_buffer_resize+0x32c/0x3dc)
|(free_snapshot+0x18/0x38)
|(tracing_set_tracer+0x27c/0x2ac)

probably via
|cd /sys/kernel/debug/tracing/
|echo 1 > events/enable ; sleep 2
|echo 1024 > buffer_size_kb

If we just always use schedule_work_on(), there's no need for the
preempt_off().  So do that.

Link: http://lkml.kernel.org/p/1405537633-31518-1-git-send-email-cminyard@mvista.com

Reported-by: Stanislav Meduna <stano@meduna.org>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 kernel/trace/ring_buffer.c | 24 ++++--------------------
 1 file changed, 4 insertions(+), 20 deletions(-)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 469af802d14e..d6b35d3a232c 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1700,22 +1700,14 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
 			if (!cpu_buffer->nr_pages_to_update)
 				continue;
 
-			/* The update must run on the CPU that is being updated. */
-			preempt_disable();
-			if (cpu == smp_processor_id() || !cpu_online(cpu)) {
+			/* Can't run something on an offline CPU. */
+			if (!cpu_online(cpu)) {
 				rb_update_pages(cpu_buffer);
 				cpu_buffer->nr_pages_to_update = 0;
 			} else {
-				/*
-				 * Can not disable preemption for schedule_work_on()
-				 * on PREEMPT_RT.
-				 */
-				preempt_enable();
 				schedule_work_on(cpu,
 						&cpu_buffer->update_pages_work);
-				preempt_disable();
 			}
-			preempt_enable();
 		}
 
 		/* wait for all the updates to complete */
@@ -1753,22 +1745,14 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
 
 		get_online_cpus();
 
-		preempt_disable();
-		/* The update must run on the CPU that is being updated. */
-		if (cpu_id == smp_processor_id() || !cpu_online(cpu_id))
+		/* Can't run something on an offline CPU. */
+		if (!cpu_online(cpu_id))
 			rb_update_pages(cpu_buffer);
 		else {
-			/*
-			 * Can not disable preemption for schedule_work_on()
-			 * on PREEMPT_RT.
-			 */
-			preempt_enable();
 			schedule_work_on(cpu_id,
 					 &cpu_buffer->update_pages_work);
 			wait_for_completion(&cpu_buffer->update_done);
-			preempt_disable();
 		}
-		preempt_enable();
 
 		cpu_buffer->nr_pages_to_update = 0;
 		put_online_cpus();
-- 
2.7.0

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[PATCH 3.12 01/39] efi: Disable interrupts around EFI calls, not in the epilog/prolog calls Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 02/39] tools: Add a "make all" rule Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 26/39] udp: properly support MSG_PEEK with truncated buffers Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 24/39] KEYS: Fix race between read and revoke Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 22/39] sctp: Prevent soft lockup when sctp_accept() is called during a timeout event Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 28/39] xen/gntdev: Grant maps should not be subject to NUMA balancing Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 36/39] MAINTAINERS: Add public mailing list for ARC Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 27/39] x86/signal: Fix restart_syscall number for x32 tasks Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 16/39] staging/dgnc: fix info leak in ioctl Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 37/39] ARC: Fix silly typo in MAINTAINERS file commit 30b9dbee895ff0d5cbf155bd1ef3f0f5992bca6f upstream. Signed-off-by: Jiri Slaby <jslaby@suse.cz> Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 25/39] KEYS: Fix keyring ref leak in join_session_keyring() Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 32/39] x86/boot: Double BOOT_HEAP_SIZE to 64KB Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 38/39] isdn_ppp: Add checks for allocation failure in isdn_ppp_open() Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 12/39] block: Always check queue limits for cloned requests Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 20/39] m68k/mm: Check for mm != NULL in do_page_fault() debug code Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 18/39] m32r: fix potential NULL-pointer dereference Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 15/39] module: remove MODULE_GENERIC_TABLE Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 23/39] USB: quirks: Fix another ELAN touchscreen Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 17/39] pm: use GFP_ATOMIC when pm core call this function Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 39/39] ppp, slip: Validate VJ compression slot parameters completely Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 30/39] KVM: PPC: Book3S HV: Prohibit setting illegal transaction state in MSR Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 21/39] m68k/mac: Make SCC reset work more reliably Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 34/39] ALSA: hda - Add Intel Lewisburg device IDs Audio Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 04/39] dlm: make posix locks interruptible Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 35/39] ALSA: hda - Apply pin fixup for HP ProBook 6550b Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 14/39] qla2xxx: Fix hardware lock/unlock issue causing kernel panic. Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 29/39] x86/xen: don't reset vcpu_info on a cancelled suspend Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:00 +0100
  [PATCH 3.12 10/39] drm/i915: Fix SRC_COPY width on 830/845g Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:10 +0100
  [PATCH 3.12 07/39] route: Use ipv4_mtu instead of raw rt_pmtu Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:10 +0100
  [PATCH 3.12 13/39] Input: aiptek - fix crash on detecting device without endpoints Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:10 +0100
  [PATCH 3.12 05/39] PCI: Drop "setting latency timer" messages Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:10 +0100
  [PATCH 3.12 11/39] lpfc: Fix null ndlp dereference in target_reset_handler Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:10 +0100
  [PATCH 3.12 09/39] ring-buffer: Always run per-cpu ring buffer resize with schedule_work_on() Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:10 +0100
  [PATCH 3.12 06/39] ipv4: Don't increase PMTU with Datagram Too Big message. Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:10 +0100
  [PATCH 3.12 03/39] ALSA: hda - Fix noise problems on Thinkpad T440s Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:10 +0100
  [PATCH 3.12 08/39] SUNRPC: Fix oops when trace sunrpc_task events in nfs client Jiri Slaby <jslaby@suse.cz> - 2016-01-25 13:10 +0100

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