| Message ID | 20140205220944.19080.26519.stgit@srivatsabhat.in.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Feb 05, 2014 at 10:09:45PM +0000, Srivatsa S. Bhat wrote: > Subsystems that want to register CPU hotplug callbacks, as well as perform > initialization for the CPUs that are already online, often do it as shown > below: [...] > Fix the hw-breakpoint code in arm64 by using this latter form of callback > registration. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will.deacon@arm.com> > Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com> > Cc: linux-arm-kernel@lists.infradead.org > Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> > --- > > arch/arm64/kernel/hw_breakpoint.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c > index f17f581..24e88d0 100644 > --- a/arch/arm64/kernel/hw_breakpoint.c > +++ b/arch/arm64/kernel/hw_breakpoint.c > @@ -913,6 +913,8 @@ static int __init arch_hw_breakpoint_init(void) > pr_info("found %d breakpoint and %d watchpoint registers.\n", > core_num_brps, core_num_wrps); > > + cpu_maps_update_begin(); > + > /* > * Reset the breakpoint resources. We assume that a halting > * debugger will leave the world in a nice state for us. > @@ -927,7 +929,10 @@ static int __init arch_hw_breakpoint_init(void) > TRAP_HWBKPT, "hw-watchpoint handler"); > > /* Register hotplug notifier. */ > - register_cpu_notifier(&hw_breakpoint_reset_nb); > + __register_cpu_notifier(&hw_breakpoint_reset_nb); > + > + cpu_maps_update_done(); > + > /* Register cpu_suspend hw breakpoint restore hook */ > cpu_suspend_set_dbg_restorer(hw_breakpoint_reset); Acked-by: Will Deacon <will.deacon@arm.com> Will
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c index f17f581..24e88d0 100644 --- a/arch/arm64/kernel/hw_breakpoint.c +++ b/arch/arm64/kernel/hw_breakpoint.c @@ -913,6 +913,8 @@ static int __init arch_hw_breakpoint_init(void) pr_info("found %d breakpoint and %d watchpoint registers.\n", core_num_brps, core_num_wrps); + cpu_maps_update_begin(); + /* * Reset the breakpoint resources. We assume that a halting * debugger will leave the world in a nice state for us. @@ -927,7 +929,10 @@ static int __init arch_hw_breakpoint_init(void) TRAP_HWBKPT, "hw-watchpoint handler"); /* Register hotplug notifier. */ - register_cpu_notifier(&hw_breakpoint_reset_nb); + __register_cpu_notifier(&hw_breakpoint_reset_nb); + + cpu_maps_update_done(); + /* Register cpu_suspend hw breakpoint restore hook */ cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);
Subsystems that want to register CPU hotplug callbacks, as well as perform initialization for the CPUs that are already online, often do it as shown below: get_online_cpus(); for_each_online_cpu(cpu) init_cpu(cpu); register_cpu_notifier(&foobar_cpu_notifier); put_online_cpus(); This is wrong, since it is prone to ABBA deadlocks involving the cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently with CPU hotplug operations). Instead, the correct and race-free way of performing the callback registration is: cpu_maps_update_begin(); for_each_online_cpu(cpu) init_cpu(cpu); /* Note the use of the double underscored version of the API */ __register_cpu_notifier(&foobar_cpu_notifier); cpu_maps_update_done(); Fix the hw-breakpoint code in arm64 by using this latter form of callback registration. Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Lorenzo Pieralisi <Lorenzo.Pieralisi@arm.com> Cc: linux-arm-kernel@lists.infradead.org Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com> --- arch/arm64/kernel/hw_breakpoint.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)