From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Breno Leitao <leitao@debian.org>,
Thiago Jung Bauermann <bauerman@linux.ibm.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Sasha Levin <sashal@kernel.org>
Subject: [PATCH 4.9 15/39] powerpc/xmon: Fix invocation inside lock region
Date: Thu, 24 Jan 2019 20:20:18 +0100 [thread overview]
Message-ID: <20190124190448.777309021@linuxfoundation.org> (raw)
In-Reply-To: <20190124190448.232316246@linuxfoundation.org>
4.9-stable review patch. If anyone has any objections, please let me know.
------------------
[ Upstream commit 8d4a862276a9c30a269d368d324fb56529e6d5fd ]
Currently xmon needs to get devtree_lock (through rtas_token()) during its
invocation (at crash time). If there is a crash while devtree_lock is being
held, then xmon tries to get the lock but spins forever and never get into
the interactive debugger, as in the following case:
int *ptr = NULL;
raw_spin_lock_irqsave(&devtree_lock, flags);
*ptr = 0xdeadbeef;
This patch avoids calling rtas_token(), thus trying to get the same lock,
at crash time. This new mechanism proposes getting the token at
initialization time (xmon_init()) and just consuming it at crash time.
This would allow xmon to be possible invoked independent of devtree_lock
being held or not.
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
arch/powerpc/xmon/xmon.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 760545519a0b..687e8b8bf5c6 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -73,6 +73,9 @@ static int xmon_gate;
#define xmon_owner 0
#endif /* CONFIG_SMP */
+#ifdef CONFIG_PPC_PSERIES
+static int set_indicator_token = RTAS_UNKNOWN_SERVICE;
+#endif
static unsigned long in_xmon __read_mostly = 0;
static unsigned long adrs;
@@ -340,7 +343,6 @@ static inline void disable_surveillance(void)
#ifdef CONFIG_PPC_PSERIES
/* Since this can't be a module, args should end up below 4GB. */
static struct rtas_args args;
- int token;
/*
* At this point we have got all the cpus we can into
@@ -349,11 +351,11 @@ static inline void disable_surveillance(void)
* If we did try to take rtas.lock there would be a
* real possibility of deadlock.
*/
- token = rtas_token("set-indicator");
- if (token == RTAS_UNKNOWN_SERVICE)
+ if (set_indicator_token == RTAS_UNKNOWN_SERVICE)
return;
- rtas_call_unlocked(&args, token, 3, 1, NULL, SURVEILLANCE_TOKEN, 0, 0);
+ rtas_call_unlocked(&args, set_indicator_token, 3, 1, NULL,
+ SURVEILLANCE_TOKEN, 0, 0);
#endif /* CONFIG_PPC_PSERIES */
}
@@ -3227,6 +3229,14 @@ static void xmon_init(int enable)
__debugger_iabr_match = xmon_iabr_match;
__debugger_break_match = xmon_break_match;
__debugger_fault_handler = xmon_fault_handler;
+
+#ifdef CONFIG_PPC_PSERIES
+ /*
+ * Get the token here to avoid trying to get a lock
+ * during the crash, causing a deadlock.
+ */
+ set_indicator_token = rtas_token("set-indicator");
+#endif
} else {
__debugger = NULL;
__debugger_ipi = NULL;
--
2.19.1
next prev parent reply other threads:[~2019-01-24 19:29 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-24 19:20 [PATCH 4.9 00/39] 4.9.153-stable review Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 01/39] r8169: Add support for new Realtek Ethernet Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 02/39] ipv6: Consider sk_bound_dev_if when binding a socket to a v4 mapped address Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 03/39] ipv6: Take rcu_read_lock in __inet6_bind for mapped addresses Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 04/39] platform/x86: asus-wmi: Tell the EC the OS will handle the display off hotkey Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 05/39] e1000e: allow non-monotonic SYSTIM readings Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 06/39] writeback: dont decrement wb->refcnt if !wb->bdi Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 07/39] serial: set suppress_bind_attrs flag only if builtin Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 08/39] ALSA: oxfw: add support for APOGEE duet FireWire Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 09/39] MIPS: SiByte: Enable swiotlb for SWARM, LittleSur and BigSur Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 10/39] arm64: perf: set suppress_bind_attrs flag to true Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 11/39] selinux: always allow mounting submounts Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 12/39] rxe: IB_WR_REG_MR does not capture MRs iova field Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 13/39] jffs2: Fix use of uninitialized delayed_work, lockdep breakage Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 14/39] pstore/ram: Do not treat empty buffers as valid Greg Kroah-Hartman
2019-01-24 19:20 ` Greg Kroah-Hartman [this message]
2019-01-24 19:20 ` [PATCH 4.9 16/39] powerpc/pseries/cpuidle: Fix preempt warning Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 17/39] media: firewire: Fix app_info parameter type in avc_ca{,_app}_info Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 18/39] net: call sk_dst_reset when set SO_DONTROUTE Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 19/39] scsi: target: use consistent left-aligned ASCII INQUIRY data Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 20/39] clk: imx6q: reset exclusive gates on init Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 21/39] kconfig: fix file name and line number of warn_ignored_character() Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 22/39] kconfig: fix memory leak when EOF is encountered in quotation Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 23/39] mmc: atmel-mci: do not assume idle after atmci_request_end Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 24/39] tty/serial: do not free trasnmit buffer page under port lock Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 25/39] perf intel-pt: Fix error with config term "pt=0" Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 26/39] perf svghelper: Fix unchecked usage of strncpy() Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 27/39] perf parse-events: " Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 28/39] dm kcopyd: Fix bug causing workqueue stalls Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 29/39] tools lib subcmd: Dont add the kernel sources to the include path Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 30/39] dm snapshot: Fix excessive memory usage and workqueue stalls Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 31/39] ALSA: bebob: fix model-id of unit for Apogee Ensemble Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 32/39] sysfs: Disable lockdep for driver bind/unbind files Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 33/39] scsi: smartpqi: correct lun reset issues Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 34/39] scsi: megaraid: fix out-of-bound array accesses Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 35/39] ocfs2: fix panic due to unrecovered local alloc Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 36/39] mm/page-writeback.c: dont break integrity writeback on ->writepage() error Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 37/39] mm, proc: be more verbose about unstable VMA flags in /proc/<pid>/smaps Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 38/39] ipmi:ssif: Fix handling of multi-part return messages Greg Kroah-Hartman
2019-01-24 19:20 ` [PATCH 4.9 39/39] locking/qspinlock: Pull in asm/byteorder.h to ensure correct endianness Greg Kroah-Hartman
2019-01-25 14:43 ` [PATCH 4.9 00/39] 4.9.153-stable review shuah
2019-01-25 16:28 ` Naresh Kamboju
2019-01-25 23:17 ` Guenter Roeck
2019-01-26 12:07 ` Jon Hunter
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