Hi Santosh, On Fri, 17 Feb 2012 13:18:37 +0530, Santosh Shilimkar <santosh.shilimkar@xxxxxx> wrote: > > From 3a16f7a6694c14e201fdf6ad195c821816b2de84 Mon Sep 17 00:00:00 2001 > From: Santosh Shilimkar <santosh.shilimkar@xxxxxx> > Date: Fri, 17 Feb 2012 11:11:28 +0530 > Subject: [PATCH] ARM: smp_twd: Don't register CPUFREQ notifiers if local > timers are not initialised. > > Current ARM local timer code registers CPUFREQ notifiers even in case > the twd_timer_setup() isn't called. That seems to be wrong and > would eventually lead to kernel crash on the CPU frequency transitions > on the SOCs where the local timer doesn't exist or broken because of > hardware BUG. > > Fix it by uisng an initialised variable. Though the twd_timer_setup() > is percpu, the idea here is to avoid the CPUFREQ registration. Hence > percpu initialised variable is not used. > > The issue was observed with v3.3-rc3 and building an OMAP2+ kernel > on OMAP3 SOC which doesn't have TWD. > > Below is the dump for reference : > > Unable to handle kernel paging request at virtual address 007e900 > pgd = cdc20000 > [007e9000] *pgd=00000000 > Internal error: Oops: 5 [#1] SMP > Modules linked in: > CPU: 0 Not tainted (3.3.0-rc3-pm+debug+initramfs #9) > PC is at twd_update_frequency+0x34/0x48 > LR is at twd_update_frequency+0x10/0x48 > pc : [<c001382c>] lr : [<c0013808>] psr: 60000093 > sp : ce311dd8 ip : 00000000 fp : 00000000 > r10: 00000000 r9 : 00000001 r8 : ce310000 > r7 : c0440458 r6 : c00137f8 r5 : 00000000 r4 : c0947a74 > r3 : 00000000 r2 : 007e9000 r1 : 00000000 r0 : 00000000 > Flags: nZCv IRQs off FIQs on Mode SVC_32 ISA ARM Segment usr > Control: 10c5387d Table: 8dc20019 DAC: 00000015 > Process sh (pid: 599, stack limit = 0xce3102f8) > Stack: (0xce311dd8 to 0xce312000) > 1dc0: 6000c > 1de0: 00000001 00000002 00000000 00000000 00000000 00000000 00000 > 1e00: ffffffff c093d8f0 00000000 ce311ebc 00000001 00000001 ce310 > 1e20: c001386c c0437c4c c0e95b60 c0e95ba8 00000001 c0e95bf8 ffff4 > 1e40: 00000000 00000000 c005ef74 ce310000 c0435cf0 ce311ebc 00000 > 1e60: ce352b40 0007a120 c08d5108 c08ba040 c08ba040 c005f030 00000 > 1e80: c08bc554 c032fe2c 0007a120 c08d4b64 ce352b40 c08d8618 ffff8 > 1ea0: c08ba040 c033364c ce311ecc c0433b50 00000002 ffffffea c0330 > 1ec0: 0007a120 0007a120 22222201 00000000 22222222 00000000 ce357 > 1ee0: ce3d6000 cdc2aed8 ce352ba0 c0470164 00000002 c032f47c 00034 > 1f00: c0331cac ce352b40 00000007 c032f6d0 ce352bbc 0003d090 c0930 > 1f20: c093d8bc c03306a4 00000007 ce311f80 00000007 cdc2aec0 ce358 > 1f40: ce8d20c0 00000007 b6fe5000 ce311f80 00000007 ce310000 0000c > 1f60: c000de74 ce987400 ce8d20c0 b6fe5000 00000000 00000000 0000c > 1f80: 00000000 00000000 001fbac8 00000000 00000007 001fbac8 00004 > 1fa0: c000df04 c000dd60 00000007 001fbac8 00000001 b6fe5000 00000 > 1fc0: 00000007 001fbac8 00000007 00000004 b6fe5000 00000000 00202 > 1fe0: 00000000 beb565f8 00101ffc 00008e8c 60000010 00000001 00000 > [<c001382c>] (twd_update_frequency+0x34/0x48) from [<c008ac4c>] ) > [<c008ac4c>] (smp_call_function_single+0x17c/0x1c8) from [<c0013) > [<c0013890>] (twd_cpufreq_transition+0x24/0x30) from [<c0437c4c>) > [<c0437c4c>] (notifier_call_chain+0x44/0x84) from [<c005efe4>] () > [<c005efe4>] (__srcu_notifier_call_chain+0x70/0xa4) from [<c005f) > [<c005f030>] (srcu_notifier_call_chain+0x18/0x20) from [<c032fe2) > [<c032fe2c>] (cpufreq_notify_transition+0xc8/0x1b0) from [<c0333) > [<c033364c>] (omap_target+0x1b4/0x28c) from [<c032f47c>] (__cpuf) > [<c032f47c>] (__cpufreq_driver_target+0x50/0x64) from [<c0331d24) > [<c0331d24>] (cpufreq_set+0x78/0x98) from [<c032f6d0>] (store_sc) > [<c032f6d0>] (store_scaling_setspeed+0x5c/0x74) from [<c03306a4>) > [<c03306a4>] (store+0x58/0x74) from [<c014d868>] (sysfs_write_fi) > [<c014d868>] (sysfs_write_file+0x80/0xb4) from [<c00f2c2c>] (vfs) > [<c00f2c2c>] (vfs_write+0xa8/0x138) from [<c00f2e9c>] (sys_write) > [<c00f2e9c>] (sys_write+0x40/0x6c) from [<c000dd60>] (ret_fast_s) > Code: e594300c e792210c e1a01000 e5840004 (e7930002) > ---[ end trace 5da3b5167c1ecdda ]--- > > Reported-by: Kevin Hilman <khilman@xxxxxx> > Signed-off-by: Santosh Shilimkar <santosh.shilimkar@xxxxxx> > --- > arch/arm/kernel/smp_twd.c | 4 +++- > 1 files changed, 3 insertions(+), 1 deletions(-) > > diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c > index 4285daa..753ae37 100644 > --- a/arch/arm/kernel/smp_twd.c > +++ b/arch/arm/kernel/smp_twd.c > @@ -30,6 +30,7 @@ void __iomem *twd_base; > > static struct clk *twd_clk; > static unsigned long twd_timer_rate; > +static bool twd_initialised; > > static struct clock_event_device __percpu **twd_evt; > > @@ -129,7 +130,7 @@ static struct notifier_block twd_cpufreq_nb = { > > static int twd_cpufreq_init(void) > { > - if (!IS_ERR(twd_clk)) > + if ((!IS_ERR(twd_clk)) && twd_initialised) > return cpufreq_register_notifier(&twd_cpufreq_nb, > CPUFREQ_TRANSITION_NOTIFIER); Testing twd_evt and *__this_cpu_ptr(twd_evt) should have a similar effect, and save the additional variable. M. -- Fast, cheap, reliable. Pick two. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html