This is a note to let you know that I've just added the patch titled clockevents/tcb_clksrc: Prevent disabling an already disabled clock to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: clockevents-tcb_clksrc-prevent-disabling-an-already-disabled-clock.patch and it can be found in the queue-4.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From f02b4b72d12cbae7020a959e2ed0410a464b4cc4 Mon Sep 17 00:00:00 2001 From: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx> Date: Fri, 15 Jan 2016 11:34:21 +0100 Subject: clockevents/tcb_clksrc: Prevent disabling an already disabled clock From: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx> commit f02b4b72d12cbae7020a959e2ed0410a464b4cc4 upstream. clockevents_exchange_device is calling clockevents_shutdown() on the new clockenvents device but it may have never been enabled in the first place. This results in the tcb clock being disabled without being enabled first: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 1 at drivers/clk/clk.c:680 clk_disable+0x28/0x34() Modules linked in: CPU: 0 PID: 1 Comm: swapper Not tainted 4.4.0+ #6 Hardware name: Atmel AT91SAM9 [<c000f2b8>] (unwind_backtrace) from [<c000d01c>] (show_stack+0x10/0x14) [<c000d01c>] (show_stack) from [<c00172f0>] (warn_slowpath_common+0x78/0xa0) [<c00172f0>] (warn_slowpath_common) from [<c00173a8>] (warn_slowpath_null+0x18/0x20) [<c00173a8>] (warn_slowpath_null) from [<c0361528>] (clk_disable+0x28/0x34) [<c0361528>] (clk_disable) from [<c034d560>] (tc_shutdown+0x38/0x4c) [<c034d560>] (tc_shutdown) from [<c0059ad4>] (clockevents_switch_state+0x38/0x6c) [<c0059ad4>] (clockevents_switch_state) from [<c0059b18>] (clockevents_shutdown+0x10/0x24) [<c0059b18>] (clockevents_shutdown) from [<c005a458>] (tick_check_new_device+0x84/0xac) [<c005a458>] (tick_check_new_device) from [<c0059660>] (clockevents_register_device+0x7c/0x108) [<c0059660>] (clockevents_register_device) from [<c06b5a68>] (tcb_clksrc_init+0x390/0x3e8) [<c06b5a68>] (tcb_clksrc_init) from [<c00097cc>] (do_one_initcall+0x114/0x1d4) [<c00097cc>] (do_one_initcall) from [<c069bd54>] (kernel_init_freeable+0xfc/0x1b8) [<c069bd54>] (kernel_init_freeable) from [<c04c3818>] (kernel_init+0x8/0xe0) [<c04c3818>] (kernel_init) from [<c000a410>] (ret_from_fork+0x14/0x24) ---[ end trace 0000000000000001 ]--- Check what state we were in before trying to disable the clock. Fixes: cf4541c101ea ("clockevents/drivers/tcb_clksrc: Migrate to new 'set-state' interface") Signed-off-by: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxxxxxxxxx> Cc: Nicolas Ferre <nicolas.ferre@xxxxxxxxx> Cc: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxxxxxxx> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> Link: http://lkml.kernel.org/r/1452854061-30370-1-git-send-email-alexandre.belloni@xxxxxxxxxxxxxxxxxx Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/clocksource/tcb_clksrc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/drivers/clocksource/tcb_clksrc.c +++ b/drivers/clocksource/tcb_clksrc.c @@ -98,7 +98,8 @@ static int tc_shutdown(struct clock_even __raw_writel(0xff, regs + ATMEL_TC_REG(2, IDR)); __raw_writel(ATMEL_TC_CLKDIS, regs + ATMEL_TC_REG(2, CCR)); - clk_disable(tcd->clk); + if (!clockevent_state_detached(d)) + clk_disable(tcd->clk); return 0; } Patches currently in stable-queue which might be from alexandre.belloni@xxxxxxxxxxxxxxxxxx are queue-4.4/clockevents-tcb_clksrc-prevent-disabling-an-already-disabled-clock.patch -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html