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The added Kconfig dependency is slightly incorrect, which can lead to a link failure when the watchdog is a loadable module: arm-linux-gnueabi-ld: drivers/rtc/rtc-bd70528.o: in function `bd70528_set_rtc_based_timers': rtc-bd70528.c:(.text+0x6cc): undefined reference to `bd70528_wdt_set' arm-linux-gnueabi-ld: drivers/rtc/rtc-bd70528.o: in function `bd70528_set_time': rtc-bd70528.c:(.text+0xaa0): undefined reference to `bd70528_wdt_lock' arm-linux-gnueabi-ld: rtc-bd70528.c:(.text+0xab8): undefined reference to `bd70528_wdt_unlock' arm-linux-gnueabi-ld: drivers/rtc/rtc-bd70528.o: in function `bd70528_alm_enable': rtc-bd70528.c:(.text+0xfc0): undefined reference to `bd70528_wdt_lock' arm-linux-gnueabi-ld: rtc-bd70528.c:(.text+0x1030): undefined reference to `bd70528_wdt_unlock' The problem is that it allows to be built-in if MFD_ROHM_BD71828 is built-in, even when the watchdog is a loadable module. Rework this so that having the watchdog as a loadable module always forces the rtc to be a module as well instead of built-in, regardless of bd71828. Fixes: c56dc06 ("rtc: bd70528: Support RTC on ROHM BD71815") Signed-off-by: Arnd Bergmann <arnd@arndb.de> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Reviewed-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210422151545.2403356-1-arnd@kernel.org
Congatec's QMX6 system on module (SoM) uses a m41t62 as RTC. The modules SQW clock output defaults to 32768 Hz. This behaviour is used to provide the i.MX6 CKIL clock. Once the RTC driver is probed, the clock is disabled and all i.MX6 functionality depending on the 32 KHz clock has undefined behaviour. For example when using the hardware watchdog the system will likely do arbitrary reboots. Referencing the m41t62 directly results in a deadlock. The kernel will see, that i.MX6 system clock needs the RTC clock and do probe deferral. But the i.MX6 I2C module never becomes usable without the i.MX6 CKIL clock and thus the RTC's clock will not be probed. So from the kernel's perspective this is a chicken-and-egg problem. Technically everything is fine by not touching anything, since the RTC clock correctly enables the clock on reset (i.e. on battery backup power loss) and also the bootloader enables it in case an something (e.g. an unpatched kernel) disabled this incorrectly. A workaround for this issue is describing the square wave pin as fixed-clock, which is registered early and basically how this pin is used on the i.MX6. Suggested-by: Saravana Kannan <saravanak@google.com> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com> Reviewed-by: Saravana Kannan <saravanak@google.com> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210428222953.235280-2-sebastian.reichel@collabora.com
This patch adds missing MODULE_DEVICE_TABLE definition which generates correct modalias for automatic loading of this driver when it is built as an external module. Reported-by: Hulk Robot <hulkci@huawei.com> Signed-off-by: Bixuan Cui <cuibixuan@huawei.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210508031509.53735-1-cuibixuan@huawei.com
Converts rtc/faraday,ftrtc01.txt to yaml. This permits to detect some missing properties: reg, resets, interrupts Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Corentin Labbe <clabbe@baylibre.com> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210510182505.3968936-1-clabbe@baylibre.com
The scnprintf() function silently truncates the printf() and returns the number bytes that it was able to copy (not counting the NUL terminator). Thus, the highest value it can return here is "NAME_SIZE - 1" and the overflow check is dead code. Fix this by using the snprintf() function which returns the number of bytes that would have been copied if there was enough space and changing the condition from "> NAME_SIZE" to ">= NAME_SIZE". Fixes: 92589c9 ("rtc-proc: permit the /proc/driver/rtc device to use other devices") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/YJov/pcGmhLi2pEl@mwanda
'MODULE_ALIAS' is declared twice, cleanup one. Cc: Alessandro Zummo <a.zummo@towertech.it> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com> Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/1621848834-20857-1-git-send-email-zhangshaokun@hisilicon.com
The DryIce-based RTC supports alarms that trigger an interrupt. Configure this interrupt as a wakeup source that wakes the system up from standby mode. Signed-off-by: Martin Kaiser <martin@kaiser.cx> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210511161244.16111-1-martin@kaiser.cx
Fix the following make W=1 kernel build warning: drivers/rtc/sysfs.c:115: warning: expecting prototype for rtc_sysfs_show_hctosys(). Prototype was for hctosys_show() instead Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210517045901.3461800-1-yangyingliang@huawei.com
Fix the following make W=1 kernel build warnings: drivers/rtc/rtc-m41t80.c:811: warning: expecting prototype for wdt_close(). Prototype was for wdt_release() instead drivers/rtc/rtc-m41t80.c:830: warning: expecting prototype for notify_sys(). Prototype was for wdt_notify_sys() instead Signed-off-by: Yang Yingliang <yangyingliang@huawei.com> Reviewed-by: Randy Dunlap <rdunlap@infradead.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210517110641.473386-1-yangyingliang@huawei.com
Interrupt line can be configured on different hardware in different way, even inverted. Therefore driver should not enforce specific trigger type - edge falling - but instead rely on Devicetree to configure it. The Maxim 77686 datasheet describes the interrupt line as active low with a requirement of acknowledge from the CPU therefore the edge falling is not correct. The interrupt line is shared between PMIC and RTC driver, so using level sensitive interrupt is here especially important to avoid races. With an edge configuration in case if first PMIC signals interrupt followed shortly after by the RTC, the interrupt might not be yet cleared/acked thus the second one would not be noticed. Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210526172036.183223-6-krzysztof.kozlowski@canonical.com
The only known BD70528 use-cases are such that the PMIC is controlled from separate MCU which is not running Linux. I am not aware of any Linux driver users. Furthermore, it seems there is no demand for this IC. Let's ease the maintenance burden and drop the driver. We can always add it back if there is sudden need for it. Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210527105819.GA3111334@localhost.localdomain
The STM32MP1 RTC may have 2 clocks, the pclk and the rtc_ck. If clk_prepare_enable() fails for the second clock (rtc_ck) we must only call clk_disable_unprepare() for the first clock (pclk) but currently we call it on both leading to a WARN: [ 15.629568] WARNING: CPU: 0 PID: 146 at drivers/clk/clk.c:958 clk_core_disable+0xb0/0xc8 [ 15.637620] ck_rtc already disabled [ 15.663322] CPU: 0 PID: 146 Comm: systemd-udevd Not tainted 5.4.77-pknbsp-svn5759-atag-v5.4.77-204-gea4235203137-dirty #2413 [ 15.674510] Hardware name: STM32 (Device Tree Support) [ 15.679658] [<c0111148>] (unwind_backtrace) from [<c010c0b8>] (show_stack+0x10/0x14) [ 15.687371] [<c010c0b8>] (show_stack) from [<c0ab3d28>] (dump_stack+0xc0/0xe0) [ 15.694574] [<c0ab3d28>] (dump_stack) from [<c012360c>] (__warn+0xc8/0xf0) [ 15.701428] [<c012360c>] (__warn) from [<c0123694>] (warn_slowpath_fmt+0x60/0x94) [ 15.708894] [<c0123694>] (warn_slowpath_fmt) from [<c053b518>] (clk_core_disable+0xb0/0xc8) [ 15.717230] [<c053b518>] (clk_core_disable) from [<c053c190>] (clk_core_disable_lock+0x18/0x24) [ 15.725924] [<c053c190>] (clk_core_disable_lock) from [<bf0adc44>] (stm32_rtc_probe+0x124/0x5e4 [rtc_stm32]) [ 15.735739] [<bf0adc44>] (stm32_rtc_probe [rtc_stm32]) from [<c05f7d4c>] (platform_drv_probe+0x48/0x98) [ 15.745095] [<c05f7d4c>] (platform_drv_probe) from [<c05f5cec>] (really_probe+0x1f0/0x458) [ 15.753338] [<c05f5cec>] (really_probe) from [<c05f61c4>] (driver_probe_device+0x70/0x1c4) [ 15.761584] [<c05f61c4>] (driver_probe_device) from [<c05f6580>] (device_driver_attach+0x58/0x60) [ 15.770439] [<c05f6580>] (device_driver_attach) from [<c05f6654>] (__driver_attach+0xcc/0x170) [ 15.779032] [<c05f6654>] (__driver_attach) from [<c05f40d8>] (bus_for_each_dev+0x58/0x7c) [ 15.787191] [<c05f40d8>] (bus_for_each_dev) from [<c05f4ffc>] (bus_add_driver+0xdc/0x1f8) [ 15.795352] [<c05f4ffc>] (bus_add_driver) from [<c05f6ed8>] (driver_register+0x7c/0x110) [ 15.803425] [<c05f6ed8>] (driver_register) from [<c01027bc>] (do_one_initcall+0x70/0x1b8) [ 15.811588] [<c01027bc>] (do_one_initcall) from [<c01a1094>] (do_init_module+0x58/0x1f8) [ 15.819660] [<c01a1094>] (do_init_module) from [<c01a0074>] (load_module+0x1e58/0x23c8) [ 15.827646] [<c01a0074>] (load_module) from [<c01a0860>] (sys_finit_module+0xa0/0xd4) [ 15.835459] [<c01a0860>] (sys_finit_module) from [<c01011e0>] (__sys_trace_return+0x0/0x20) Signed-off-by: Martin Fuzzey <martin.fuzzey@flowbird.group> Fixes: 4e64350 ("rtc: add STM32 RTC driver") Cc: stable@vger.kernel.org Reviewed-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/1623087421-19722-1-git-send-email-martin.fuzzey@flowbird.group
The variable retval is being initialized with a value that is never read,
it is being updated later on. The assignment is redundant and can be
removed.
Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20210609120050.185746-1-colin.king@canonical.com
Convert the Epson RX8900 DT bindings to YAML schema. Signed-off-by: Marek Vasut <marex@denx.de> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com> Cc: Rob Herring <robh+dt@kernel.org> Cc: kernel@dh-electronics.com Cc: linux-rtc@vger.kernel.org To: devicetree@vger.kernel.org Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210610150044.29792-1-marex@denx.de
Convert the TI BQ32000 I2C Serial Real-Time Clock Device Tree binding documentation to json-schema. Document missing properties. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/42d9c71b4ee1f120e0cdcf6b266547d29d1fb9a4.1623851377.git.geert+renesas@glider.be
The current datasheet URL is no longer valid. Replace with a valid one. Signed-off-by: Fabio Estevam <festevam@gmail.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210603143447.2223353-1-festevam@gmail.com
The current datasheet URL is no longer valid. Replace with a valid one. Signed-off-by: Fabio Estevam <festevam@gmail.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210603143447.2223353-2-festevam@gmail.com
The current datasheet URL is no longer valid. Replace with a valid one. Signed-off-by: Fabio Estevam <festevam@gmail.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210603143447.2223353-3-festevam@gmail.com
Take maintainership of the binding as PAvel said he doesn't have the hardware anymore. Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Acked-by: Pavel Machek <pavel@ucw.cz> Link: https://lore.kernel.org/r/20210620224030.1115356-1-alexandre.belloni@bootlin.com
After updating the datasheet URL, the PCF85063A datasheet revision has changed. Adjust it accordingly. Reported-by: Nobuhiro Iwamatsu <iwamatsu@nigauri.org> Signed-off-by: Fabio Estevam <festevam@gmail.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210624120953.2313378-1-festevam@gmail.com
Use SPDX-License-Identifier instead of a verbose license text. Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210707075804.337458-2-nobuhiro1.iwamatsu@toshiba.co.jp
Use SPDX-License-Identifier instead of a verbose license text. Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210707075804.337458-3-nobuhiro1.iwamatsu@toshiba.co.jp
Use SPDX-License-Identifier instead of a verbose license text. Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210707075804.337458-4-nobuhiro1.iwamatsu@toshiba.co.jp
Use SPDX-License-Identifier instead of a verbose license text. Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210707075804.337458-5-nobuhiro1.iwamatsu@toshiba.co.jp
For C files, use the C99 format (//). Cc: Orson Zhai <orsonzhai@gmail.com> Cc: Baolin Wang <baolin.wang7@gmail.com> Cc: Chunyan Zhang <zhang.lyra@gmail.com> Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210707075804.337458-6-nobuhiro1.iwamatsu@toshiba.co.jp
For C files, use the C99 format (//). Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210707075804.337458-7-nobuhiro1.iwamatsu@toshiba.co.jp
Use SPDX-License-Identifier instead of a verbose license text. Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210707075804.337458-8-nobuhiro1.iwamatsu@toshiba.co.jp
Use SPDX-License-Identifier instead of a verbose license text. Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210707075804.337458-9-nobuhiro1.iwamatsu@toshiba.co.jp
Use SPDX-License-Identifier instead of a verbose license text. Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210707075804.337458-11-nobuhiro1.iwamatsu@toshiba.co.jp
s5m_check_peding_alarm_interrupt() in s5m_rtc_read_alarm() gets the return value, but doesn't use it. This modifies using the s5m_check_peding_alarm_interrupt()"s return value as the s5m_rtc_read_alarm()'s return value. Cc: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com> Cc: linux-samsung-soc@vger.kernel.org Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210708051304.341278-1-nobuhiro1.iwamatsu@toshiba.co.jp
The offset variable is checked by at91_rtc_readalarm(), but this check is unnecessary because the previous check knew that the value of this variable was not 0. This removes that unnecessary offset variable checks. Cc: Nicolas Ferre <nicolas.ferre@microchip.com> Cc: Ludovic Desroches <ludovic.desroches@microchip.com> Signed-off-by: Nobuhiro Iwamatsu <nobuhiro1.iwamatsu@toshiba.co.jp> Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210708051340.341345-1-nobuhiro1.iwamatsu@toshiba.co.jp
commit 03623b4 ("rtc: pcf2127: add tamper detection support") added support for timestamp interrupts. However they are not being handled in the irq handler. If a timestamp interrupt occurs it results in kernel disabling the interrupt and displaying the call trace: [ 121.145580] irq 78: nobody cared (try booting with the "irqpoll" option) ... [ 121.238087] [<00000000c4d69393>] irq_default_primary_handler threaded [<000000000a90d25b>] pcf2127_rtc_irq [rtc_pcf2127] [ 121.248971] Disabling IRQ #78 Handle timestamp interrupts in pcf2127_rtc_irq(). Save time stamp before clearing TSF1 and TSF2 flags so that it can't be overwritten. Set a flag to mark if the timestamp is valid and only report to sysfs if the flag is set. To mimic the hardware behavior, don’t save another timestamp until the first one has been read by the userspace. However, if the alarm irq is not configured, keep the old way of handling timestamp interrupt in the timestamp0 sysfs calls. Signed-off-by: Mian Yousaf Kaukab <ykaukab@suse.de> Reviewed-by: Bruno Thomsen <bruno.thomsen@gmail.com> Tested-by: Bruno Thomsen <bruno.thomsen@gmail.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210629150643.31551-1-ykaukab@suse.de
arch/arm/mach-ixp4xx/include/mach/platform.h now gets included indirectly and defines REG_OFFSET. Rename the register and bit definition to something specific to the driver. Fixes: 7fd70c6 ("ARM: irqstat: Get rid of duplicated declaration") Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com> Link: https://lore.kernel.org/r/20210710211431.1393589-1-alexandre.belloni@bootlin.com
Commit dbbee9d ("mm/page_alloc: convert per-cpu list protection to local_lock") folded in a workaround patch for pahole that was unable to deal with zero-sized percpu structures. A superior workaround is achieved with commit a0b8200 ("kbuild: skip per-CPU BTF generation for pahole v1.18-v1.21"). This patch reverts the dummy field and the pahole version check. Fixes: dbbee9d ("mm/page_alloc: convert per-cpu list protection to local_lock") Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
…/abelloni/linux
Pull RTC updates from Alexandre Belloni:
"Mostly documentation/comment changes and non urgent fixes.
- add or fix SPDX identifiers
- NXP pcf*: fix datasheet URLs
- imxdi: add wakeup support
- pcf2127: handle timestamp interrupts, this fixes a possible
interrupt storm
- bd70528: Drop BD70528 support"
* tag 'rtc-5.14' of git://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux: (33 commits)
rtc: pcf8523: rename register and bit defines
rtc: pcf2127: handle timestamp interrupts
rtc: at91sam9: Remove unnecessary offset variable checks
rtc: s5m: Check return value of s5m_check_peding_alarm_interrupt()
rtc: spear: convert to SPDX identifier
rtc: tps6586x: convert to SPDX identifier
rtc: tps80031: convert to SPDX identifier
rtc: rtd119x: Fix format of SPDX identifier
rtc: sc27xx: Fix format of SPDX identifier
rtc: palmas: convert to SPDX identifier
rtc: max6900: convert to SPDX identifier
rtc: ds1374: convert to SPDX identifier
rtc: au1xxx: convert to SPDX identifier
rtc: pcf85063: Update the PCF85063A datasheet revision
dt-bindings: rtc: ti,bq32k: take maintainership
rtc: pcf8563: Fix the datasheet URL
rtc: pcf85063: Fix the datasheet URL
rtc: pcf2127: Fix the datasheet URL
dt-bindings: rtc: ti,bq32k: Convert to json-schema
dt-bindings: rtc: rx8900: Convert to YAML schema
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May 31, 2025
Running a modified trace-cmd record --nosplice where it does a mmap of the ring buffer when '--nosplice' is set, caused the following lockdep splat: ====================================================== WARNING: possible circular locking dependency detected 6.15.0-rc7-test-00002-gfb7d03d8a82f #551 Not tainted ------------------------------------------------------ trace-cmd/1113 is trying to acquire lock: ffff888100062888 (&buffer->mutex){+.+.}-{4:4}, at: ring_buffer_map+0x11c/0xe70 but task is already holding lock: ffff888100a5f9f8 (&cpu_buffer->mapping_lock){+.+.}-{4:4}, at: ring_buffer_map+0xcf/0xe70 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #5 (&cpu_buffer->mapping_lock){+.+.}-{4:4}: __mutex_lock+0x192/0x18c0 ring_buffer_map+0xcf/0xe70 tracing_buffers_mmap+0x1c4/0x3b0 __mmap_region+0xd8d/0x1f70 do_mmap+0x9d7/0x1010 vm_mmap_pgoff+0x20b/0x390 ksys_mmap_pgoff+0x2e9/0x440 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #4 (&mm->mmap_lock){++++}-{4:4}: __might_fault+0xa5/0x110 _copy_to_user+0x22/0x80 _perf_ioctl+0x61b/0x1b70 perf_ioctl+0x62/0x90 __x64_sys_ioctl+0x134/0x190 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #3 (&cpuctx_mutex){+.+.}-{4:4}: __mutex_lock+0x192/0x18c0 perf_event_init_cpu+0x325/0x7c0 perf_event_init+0x52a/0x5b0 start_kernel+0x263/0x3e0 x86_64_start_reservations+0x24/0x30 x86_64_start_kernel+0x95/0xa0 common_startup_64+0x13e/0x141 -> #2 (pmus_lock){+.+.}-{4:4}: __mutex_lock+0x192/0x18c0 perf_event_init_cpu+0xb7/0x7c0 cpuhp_invoke_callback+0x2c0/0x1030 __cpuhp_invoke_callback_range+0xbf/0x1f0 _cpu_up+0x2e7/0x690 cpu_up+0x117/0x170 cpuhp_bringup_mask+0xd5/0x120 bringup_nonboot_cpus+0x13d/0x170 smp_init+0x2b/0xf0 kernel_init_freeable+0x441/0x6d0 kernel_init+0x1e/0x160 ret_from_fork+0x34/0x70 ret_from_fork_asm+0x1a/0x30 -> #1 (cpu_hotplug_lock){++++}-{0:0}: cpus_read_lock+0x2a/0xd0 ring_buffer_resize+0x610/0x14e0 __tracing_resize_ring_buffer.part.0+0x42/0x120 tracing_set_tracer+0x7bd/0xa80 tracing_set_trace_write+0x132/0x1e0 vfs_write+0x21c/0xe80 ksys_write+0xf9/0x1c0 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e -> #0 (&buffer->mutex){+.+.}-{4:4}: __lock_acquire+0x1405/0x2210 lock_acquire+0x174/0x310 __mutex_lock+0x192/0x18c0 ring_buffer_map+0x11c/0xe70 tracing_buffers_mmap+0x1c4/0x3b0 __mmap_region+0xd8d/0x1f70 do_mmap+0x9d7/0x1010 vm_mmap_pgoff+0x20b/0x390 ksys_mmap_pgoff+0x2e9/0x440 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e other info that might help us debug this: Chain exists of: &buffer->mutex --> &mm->mmap_lock --> &cpu_buffer->mapping_lock Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&cpu_buffer->mapping_lock); lock(&mm->mmap_lock); lock(&cpu_buffer->mapping_lock); lock(&buffer->mutex); *** DEADLOCK *** 2 locks held by trace-cmd/1113: #0: ffff888106b847e0 (&mm->mmap_lock){++++}-{4:4}, at: vm_mmap_pgoff+0x192/0x390 #1: ffff888100a5f9f8 (&cpu_buffer->mapping_lock){+.+.}-{4:4}, at: ring_buffer_map+0xcf/0xe70 stack backtrace: CPU: 5 UID: 0 PID: 1113 Comm: trace-cmd Not tainted 6.15.0-rc7-test-00002-gfb7d03d8a82f #551 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x6e/0xa0 print_circular_bug.cold+0x178/0x1be check_noncircular+0x146/0x160 __lock_acquire+0x1405/0x2210 lock_acquire+0x174/0x310 ? ring_buffer_map+0x11c/0xe70 ? ring_buffer_map+0x11c/0xe70 ? __mutex_lock+0x169/0x18c0 __mutex_lock+0x192/0x18c0 ? ring_buffer_map+0x11c/0xe70 ? ring_buffer_map+0x11c/0xe70 ? function_trace_call+0x296/0x370 ? __pfx___mutex_lock+0x10/0x10 ? __pfx_function_trace_call+0x10/0x10 ? __pfx___mutex_lock+0x10/0x10 ? _raw_spin_unlock+0x2d/0x50 ? ring_buffer_map+0x11c/0xe70 ? ring_buffer_map+0x11c/0xe70 ? __mutex_lock+0x5/0x18c0 ring_buffer_map+0x11c/0xe70 ? do_raw_spin_lock+0x12d/0x270 ? find_held_lock+0x2b/0x80 ? _raw_spin_unlock+0x2d/0x50 ? rcu_is_watching+0x15/0xb0 ? _raw_spin_unlock+0x2d/0x50 ? trace_preempt_on+0xd0/0x110 tracing_buffers_mmap+0x1c4/0x3b0 __mmap_region+0xd8d/0x1f70 ? ring_buffer_lock_reserve+0x99/0xff0 ? __pfx___mmap_region+0x10/0x10 ? ring_buffer_lock_reserve+0x99/0xff0 ? __pfx_ring_buffer_lock_reserve+0x10/0x10 ? __pfx_ring_buffer_lock_reserve+0x10/0x10 ? bpf_lsm_mmap_addr+0x4/0x10 ? security_mmap_addr+0x46/0xd0 ? lock_is_held_type+0xd9/0x130 do_mmap+0x9d7/0x1010 ? 0xffffffffc0370095 ? __pfx_do_mmap+0x10/0x10 vm_mmap_pgoff+0x20b/0x390 ? __pfx_vm_mmap_pgoff+0x10/0x10 ? 0xffffffffc0370095 ksys_mmap_pgoff+0x2e9/0x440 do_syscall_64+0x79/0x1c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7fb0963a7de2 Code: 00 00 00 0f 1f 44 00 00 41 f7 c1 ff 0f 00 00 75 27 55 89 cd 53 48 89 fb 48 85 ff 74 3b 41 89 ea 48 89 df b8 09 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 76 5b 5d c3 0f 1f 00 48 8b 05 e1 9f 0d 00 64 RSP: 002b:00007ffdcc8fb878 EFLAGS: 00000246 ORIG_RAX: 0000000000000009 RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb0963a7de2 RDX: 0000000000000001 RSI: 0000000000001000 RDI: 0000000000000000 RBP: 0000000000000001 R08: 0000000000000006 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000000 R13: 00007ffdcc8fbe68 R14: 00007fb096628000 R15: 00005633e01a5c90 </TASK> The issue is that cpus_read_lock() is taken within buffer->mutex. The memory mapped pages are taken with the mmap_lock held. The buffer->mutex is taken within the cpu_buffer->mapping_lock. There's quite a chain with all these locks, where the deadlock can be fixed by moving the cpus_read_lock() outside the taking of the buffer->mutex. Cc: stable@vger.kernel.org Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Vincent Donnefort <vdonnefort@google.com> Link: https://lore.kernel.org/20250527105820.0f45d045@gandalf.local.home Fixes: 117c392 ("ring-buffer: Introducing ring-buffer mapping functions") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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