I'll try to test this, but I have one comment inline... On 08/11/2016 10:17 PM, Dave Young wrote: > On 08/10/16 at 05:09pm, Hidehiro Kawai wrote: >> Daniel Walker reported problems which happens when >> crash_kexec_post_notifiers kernel option is enabled >> (https://lkml.org/lkml/2015/6/24/44). >> >> In that case, smp_send_stop() is called before entering kdump routines >> which assume other CPUs are still online. As the result, kdump >> routines fail to save other CPUs' registers. Additionally for MIPS >> OCTEON, it misses to stop the watchdog timer. >> >> To fix this problem, call a new kdump friendly function, >> crash_smp_send_stop(), instead of the smp_send_stop() when >> crash_kexec_post_notifiers is enabled. crash_smp_send_stop() is a >> weak function, and it just call smp_send_stop(). Architecture >> codes should override it so that kdump can work appropriately. >> This patch provides MIPS version. >> >> Reported-by: Daniel Walker <dwalker at fifo99.com> >> Fixes: f06e5153f4ae (kernel/panic.c: add "crash_kexec_post_notifiers" option) >> Signed-off-by: Hidehiro Kawai <hidehiro.kawai.ez at hitachi.com> >> Cc: Ralf Baechle <ralf at linux-mips.org> >> Cc: David Daney <david.daney at cavium.com> >> Cc: Aaro Koskinen <aaro.koskinen at iki.fi> >> Cc: "Steven J. Hill" <steven.hill at cavium.com> >> Cc: Corey Minyard <cminyard at mvista.com> >> >> --- >> I'm not familiar with MIPS, and I don't have a test environment and >> just did build tests only. Please don't apply this patch until >> someone does enough tests, otherwise simply drop this patch. >> --- >> arch/mips/cavium-octeon/setup.c | 14 ++++++++++++++ >> arch/mips/include/asm/kexec.h | 1 + >> arch/mips/kernel/crash.c | 18 +++++++++++++++++- >> arch/mips/kernel/machine_kexec.c | 1 + >> 4 files changed, 33 insertions(+), 1 deletion(-) >> >> diff --git a/arch/mips/cavium-octeon/setup.c b/arch/mips/cavium-octeon/setup.c >> index cb16fcc..5537f95 100644 >> --- a/arch/mips/cavium-octeon/setup.c >> +++ b/arch/mips/cavium-octeon/setup.c >> @@ -267,6 +267,17 @@ static void octeon_crash_shutdown(struct pt_regs *regs) >> default_machine_crash_shutdown(regs); >> } >> >> +#ifdef CONFIG_SMP >> +void octeon_crash_smp_send_stop(void) >> +{ >> + int cpu; >> + >> + /* disable watchdogs */ >> + for_each_online_cpu(cpu) >> + cvmx_write_csr(CVMX_CIU_WDOGX(cpu_logical_map(cpu)), 0); >> +} >> +#endif >> + >> #endif /* CONFIG_KEXEC */ >> >> #ifdef CONFIG_CAVIUM_RESERVE32 >> @@ -911,6 +922,9 @@ void __init prom_init(void) >> _machine_kexec_shutdown = octeon_shutdown; >> _machine_crash_shutdown = octeon_crash_shutdown; >> _machine_kexec_prepare = octeon_kexec_prepare; >> +#ifdef CONFIG_SMP >> + _crash_smp_send_stop = octeon_crash_smp_send_stop; >> +#endif >> #endif >> >> octeon_user_io_init(); >> diff --git a/arch/mips/include/asm/kexec.h b/arch/mips/include/asm/kexec.h >> index ee25ebb..493a3cc 100644 >> --- a/arch/mips/include/asm/kexec.h >> +++ b/arch/mips/include/asm/kexec.h >> @@ -45,6 +45,7 @@ extern const unsigned char kexec_smp_wait[]; >> extern unsigned long secondary_kexec_args[4]; >> extern void (*relocated_kexec_smp_wait) (void *); >> extern atomic_t kexec_ready_to_reboot; >> +extern void (*_crash_smp_send_stop)(void); >> #endif >> #endif >> >> diff --git a/arch/mips/kernel/crash.c b/arch/mips/kernel/crash.c >> index 610f0f3..1723b17 100644 >> --- a/arch/mips/kernel/crash.c >> +++ b/arch/mips/kernel/crash.c >> @@ -47,9 +47,14 @@ static void crash_shutdown_secondary(void *passed_regs) >> >> static void crash_kexec_prepare_cpus(void) >> { >> + static int cpus_stopped; >> unsigned int msecs; >> + unsigned int ncpus; >> >> - unsigned int ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */ >> + if (cpus_stopped) >> + return; Wouldn't you want an atomic operation and some special handling here to ensure that only one CPU does this? So if a CPU comes in here and another CPU is already in the process stopping the CPUs it won't result in a deadlock. -corey >> + >> + ncpus = num_online_cpus() - 1;/* Excluding the panic cpu */ >> >> dump_send_ipi(crash_shutdown_secondary); >> smp_wmb(); >> @@ -64,6 +69,17 @@ static void crash_kexec_prepare_cpus(void) >> cpu_relax(); >> mdelay(1); >> } >> + >> + cpus_stopped = 1; >> +} >> + >> +/* Override the weak function in kernel/panic.c */ >> +void crash_smp_send_stop(void) >> +{ >> + if (_crash_smp_send_stop) >> + _crash_smp_send_stop(); >> + >> + crash_kexec_prepare_cpus(); >> } >> >> #else /* !defined(CONFIG_SMP) */ >> diff --git a/arch/mips/kernel/machine_kexec.c b/arch/mips/kernel/machine_kexec.c >> index 50980bf3..5972520 100644 >> --- a/arch/mips/kernel/machine_kexec.c >> +++ b/arch/mips/kernel/machine_kexec.c >> @@ -25,6 +25,7 @@ void (*_machine_crash_shutdown)(struct pt_regs *regs) = NULL; >> #ifdef CONFIG_SMP >> void (*relocated_kexec_smp_wait) (void *); >> atomic_t kexec_ready_to_reboot = ATOMIC_INIT(0); >> +void (*_crash_smp_send_stop)(void) = NULL; >> #endif >> >> int >> >> > Can any mips people review this patch and have a test? > > Thanks > Dave >
