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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, pierre.gondois@arm.com,
	"Steven Rostedt (VMware)" <rostedt@goodmis.org>
Subject: [PATCH 4.4 02/35] fgraph: Initialize tracing_graph_pause at task creation
Date: Mon, 22 Feb 2021 13:35:58 +0100
Message-ID: <20210222121017.542227125@linuxfoundation.org> (raw)
In-Reply-To: <20210222121013.581198717@linuxfoundation.org>

From: Steven Rostedt (VMware) <rostedt@goodmis.org>

commit 7e0a9220467dbcfdc5bc62825724f3e52e50ab31 upstream.

On some archs, the idle task can call into cpu_suspend(). The cpu_suspend()
will disable or pause function graph tracing, as there's some paths in
bringing down the CPU that can have issues with its return address being
modified. The task_struct structure has a "tracing_graph_pause" atomic
counter, that when set to something other than zero, the function graph
tracer will not modify the return address.

The problem is that the tracing_graph_pause counter is initialized when the
function graph tracer is enabled. This can corrupt the counter for the idle
task if it is suspended in these architectures.

   CPU 1				CPU 2
   -----				-----
  do_idle()
    cpu_suspend()
      pause_graph_tracing()
          task_struct->tracing_graph_pause++ (0 -> 1)

				start_graph_tracing()
				  for_each_online_cpu(cpu) {
				    ftrace_graph_init_idle_task(cpu)
				      task-struct->tracing_graph_pause = 0 (1 -> 0)

      unpause_graph_tracing()
          task_struct->tracing_graph_pause-- (0 -> -1)

The above should have gone from 1 to zero, and enabled function graph
tracing again. But instead, it is set to -1, which keeps it disabled.

There's no reason that the field tracing_graph_pause on the task_struct can
not be initialized at boot up.

Cc: stable@vger.kernel.org
Fixes: 380c4b1411ccd ("tracing/function-graph-tracer: append the tracing_graph_flag")
Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=211339
Reported-by: pierre.gondois@arm.com
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 include/linux/ftrace.h |    4 +++-
 kernel/trace/ftrace.c  |    2 --
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/include/linux/ftrace.h
+++ b/include/linux/ftrace.h
@@ -747,7 +747,9 @@ typedef int (*trace_func_graph_ent_t)(st
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 
 /* for init task */
-#define INIT_FTRACE_GRAPH		.ret_stack = NULL,
+#define INIT_FTRACE_GRAPH				\
+	.ret_stack		= NULL,			\
+	.tracing_graph_pause	= ATOMIC_INIT(0),
 
 /*
  * Stack of return addresses for functions
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -5708,7 +5708,6 @@ static int alloc_retstack_tasklist(struc
 		}
 
 		if (t->ret_stack == NULL) {
-			atomic_set(&t->tracing_graph_pause, 0);
 			atomic_set(&t->trace_overrun, 0);
 			t->curr_ret_stack = -1;
 			/* Make sure the tasks see the -1 first: */
@@ -5920,7 +5919,6 @@ static DEFINE_PER_CPU(struct ftrace_ret_
 static void
 graph_init_task(struct task_struct *t, struct ftrace_ret_stack *ret_stack)
 {
-	atomic_set(&t->tracing_graph_pause, 0);
 	atomic_set(&t->trace_overrun, 0);
 	t->ftrace_timestamp = 0;
 	/* make curr_ret_stack visible before we add the ret_stack */



  parent reply index

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-22 12:35 [PATCH 4.4 00/35] 4.4.258-rc1 review Greg Kroah-Hartman
2021-02-22 12:35 ` [PATCH 4.4 01/35] tracing: Do not count ftrace events in top level enable output Greg Kroah-Hartman
2021-02-22 12:35 ` Greg Kroah-Hartman [this message]
2021-02-22 12:35 ` [PATCH 4.4 03/35] af_key: relax availability checks for skb size calculation Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 04/35] iwlwifi: pcie: add a NULL check in iwl_pcie_txq_unmap Greg Kroah-Hartman
2021-02-25  6:04   ` Nobuhiro Iwamatsu
2021-02-25  8:14     ` Greg Kroah-Hartman
2021-02-25  8:47       ` Nobuhiro Iwamatsu
2021-02-22 12:36 ` [PATCH 4.4 05/35] iwlwifi: mvm: guard against device removal in reprobe Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 06/35] SUNRPC: Move simple_get_bytes and simple_get_netobj into private header Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 07/35] SUNRPC: Handle 0 length opaque XDR object data properly Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 08/35] lib/string: Add strscpy_pad() function Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 09/35] include/trace/events/writeback.h: fix -Wstringop-truncation warnings Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 10/35] memcg: fix a crash in wb_workfn when a device disappears Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 11/35] squashfs: add more sanity checks in id lookup Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 12/35] squashfs: add more sanity checks in inode lookup Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 13/35] squashfs: add more sanity checks in xattr id lookup Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 14/35] memblock: do not start bottom-up allocations with kernel_end Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 15/35] netfilter: xt_recent: Fix attempt to update deleted entry Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 16/35] h8300: fix PREEMPTION build, TI_PRE_COUNT undefined Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 17/35] usb: dwc3: ulpi: fix checkpatch warning Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 18/35] usb: dwc3: ulpi: Replace CPU-based busyloop with Protocol-based one Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 19/35] net: watchdog: hold device global xmit lock during tx disable Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 20/35] vsock: fix locking in vsock_shutdown() Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 21/35] x86/build: Disable CET instrumentation in the kernel for 32-bit too Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 22/35] trace: Use -mcount-record for dynamic ftrace Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 23/35] tracing: Fix SKIP_STACK_VALIDATION=1 build due to bad merge with -mrecord-mcount Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 24/35] tracing: Avoid calling cc-option -mrecord-mcount for every Makefile Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 25/35] Xen/x86: dont bail early from clear_foreign_p2m_mapping() Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 26/35] Xen/x86: also check kernel mapping in set_foreign_p2m_mapping() Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 27/35] Xen/gntdev: correct dev_bus_addr handling in gntdev_map_grant_pages() Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 28/35] Xen/gntdev: correct error checking " Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 29/35] xen/arm: dont ignore return errors from set_phys_to_machine Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 30/35] xen-blkback: dont "handle" error by BUG() Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 31/35] xen-netback: " Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 32/35] xen-scsiback: " Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 33/35] xen-blkback: fix error handling in xen_blkbk_map() Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 34/35] scsi: qla2xxx: Fix crash during driver load on big endian machines Greg Kroah-Hartman
2021-02-22 12:36 ` [PATCH 4.4 35/35] kvm: check tlbs_dirty directly Greg Kroah-Hartman
2021-02-22 18:37 ` [PATCH 4.4 00/35] 4.4.258-rc1 review Pavel Machek
2021-02-22 21:26 ` Guenter Roeck
2021-02-23 12:13 ` Naresh Kamboju
2021-02-23 21:26 ` Shuah Khan

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