| Message ID | 4CA0EEF0.70402@austin.ibm.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
In the next patch, you introduce a mutex for adding/removing memory blocks. Is there really a need for this to be atomic? If you reorder the patches so the mutex comes first, would the atomic be needed any longer? Robin On Mon, Sep 27, 2010 at 02:22:24PM -0500, Nathan Fontenot wrote: > Add a section count property to the memory_block struct to track the number > of memory sections that have been added/removed from a memory block. This > allows us to know when the last memory section of a memory block has been > removed so we can remove the memory block. > > Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com> > > --- > drivers/base/memory.c | 16 ++++++++++------ > include/linux/memory.h | 3 +++ > 2 files changed, 13 insertions(+), 6 deletions(-) > > Index: linux-next/drivers/base/memory.c > =================================================================== > --- linux-next.orig/drivers/base/memory.c 2010-09-27 09:17:20.000000000 -0500 > +++ linux-next/drivers/base/memory.c 2010-09-27 09:31:35.000000000 -0500 > @@ -478,6 +478,7 @@ > > mem->phys_index = __section_nr(section); > mem->state = state; > + atomic_inc(&mem->section_count); > mutex_init(&mem->state_mutex); > start_pfn = section_nr_to_pfn(mem->phys_index); > mem->phys_device = arch_get_memory_phys_device(start_pfn); > @@ -505,12 +506,15 @@ > struct memory_block *mem; > > mem = find_memory_block(section); > - unregister_mem_sect_under_nodes(mem); > - mem_remove_simple_file(mem, phys_index); > - mem_remove_simple_file(mem, state); > - mem_remove_simple_file(mem, phys_device); > - mem_remove_simple_file(mem, removable); > - unregister_memory(mem, section); > + > + if (atomic_dec_and_test(&mem->section_count)) { > + unregister_mem_sect_under_nodes(mem); > + mem_remove_simple_file(mem, phys_index); > + mem_remove_simple_file(mem, state); > + mem_remove_simple_file(mem, phys_device); > + mem_remove_simple_file(mem, removable); > + unregister_memory(mem, section); > + } > > return 0; > } > Index: linux-next/include/linux/memory.h > =================================================================== > --- linux-next.orig/include/linux/memory.h 2010-09-27 09:17:20.000000000 -0500 > +++ linux-next/include/linux/memory.h 2010-09-27 09:22:56.000000000 -0500 > @@ -19,10 +19,13 @@ > #include <linux/node.h> > #include <linux/compiler.h> > #include <linux/mutex.h> > +#include <asm/atomic.h> > > struct memory_block { > unsigned long phys_index; > unsigned long state; > + atomic_t section_count; > + > /* > * This serializes all state change requests. It isn't > * held during creation because the control files are > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
On 09/28/2010 04:31 AM, Robin Holt wrote: > In the next patch, you introduce a mutex for adding/removing memory blocks. > Is there really a need for this to be atomic? If you reorder the patches > so the mutex comes first, would the atomic be needed any longer? > I think you're right. Looking at the code with all patches applied I am only updating the atomic when holding the mem_sysfs_mutex. I think the atomic could safely be changed to a regular int. -Nathan > Robin > > On Mon, Sep 27, 2010 at 02:22:24PM -0500, Nathan Fontenot wrote: >> Add a section count property to the memory_block struct to track the number >> of memory sections that have been added/removed from a memory block. This >> allows us to know when the last memory section of a memory block has been >> removed so we can remove the memory block. >> >> Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com> >> >> --- >> drivers/base/memory.c | 16 ++++++++++------ >> include/linux/memory.h | 3 +++ >> 2 files changed, 13 insertions(+), 6 deletions(-) >> >> Index: linux-next/drivers/base/memory.c >> =================================================================== >> --- linux-next.orig/drivers/base/memory.c 2010-09-27 09:17:20.000000000 -0500 >> +++ linux-next/drivers/base/memory.c 2010-09-27 09:31:35.000000000 -0500 >> @@ -478,6 +478,7 @@ >> >> mem->phys_index = __section_nr(section); >> mem->state = state; >> + atomic_inc(&mem->section_count); >> mutex_init(&mem->state_mutex); >> start_pfn = section_nr_to_pfn(mem->phys_index); >> mem->phys_device = arch_get_memory_phys_device(start_pfn); >> @@ -505,12 +506,15 @@ >> struct memory_block *mem; >> >> mem = find_memory_block(section); >> - unregister_mem_sect_under_nodes(mem); >> - mem_remove_simple_file(mem, phys_index); >> - mem_remove_simple_file(mem, state); >> - mem_remove_simple_file(mem, phys_device); >> - mem_remove_simple_file(mem, removable); >> - unregister_memory(mem, section); >> + >> + if (atomic_dec_and_test(&mem->section_count)) { >> + unregister_mem_sect_under_nodes(mem); >> + mem_remove_simple_file(mem, phys_index); >> + mem_remove_simple_file(mem, state); >> + mem_remove_simple_file(mem, phys_device); >> + mem_remove_simple_file(mem, removable); >> + unregister_memory(mem, section); >> + } >> >> return 0; >> } >> Index: linux-next/include/linux/memory.h >> =================================================================== >> --- linux-next.orig/include/linux/memory.h 2010-09-27 09:17:20.000000000 -0500 >> +++ linux-next/include/linux/memory.h 2010-09-27 09:22:56.000000000 -0500 >> @@ -19,10 +19,13 @@ >> #include <linux/node.h> >> #include <linux/compiler.h> >> #include <linux/mutex.h> >> +#include <asm/atomic.h> >> >> struct memory_block { >> unsigned long phys_index; >> unsigned long state; >> + atomic_t section_count; >> + >> /* >> * This serializes all state change requests. It isn't >> * held during creation because the control files are >> >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html >> Please read the FAQ at http://www.tux.org/lkml/
Index: linux-next/drivers/base/memory.c =================================================================== --- linux-next.orig/drivers/base/memory.c 2010-09-27 09:17:20.000000000 -0500 +++ linux-next/drivers/base/memory.c 2010-09-27 09:31:35.000000000 -0500 @@ -478,6 +478,7 @@ mem->phys_index = __section_nr(section); mem->state = state; + atomic_inc(&mem->section_count); mutex_init(&mem->state_mutex); start_pfn = section_nr_to_pfn(mem->phys_index); mem->phys_device = arch_get_memory_phys_device(start_pfn); @@ -505,12 +506,15 @@ struct memory_block *mem; mem = find_memory_block(section); - unregister_mem_sect_under_nodes(mem); - mem_remove_simple_file(mem, phys_index); - mem_remove_simple_file(mem, state); - mem_remove_simple_file(mem, phys_device); - mem_remove_simple_file(mem, removable); - unregister_memory(mem, section); + + if (atomic_dec_and_test(&mem->section_count)) { + unregister_mem_sect_under_nodes(mem); + mem_remove_simple_file(mem, phys_index); + mem_remove_simple_file(mem, state); + mem_remove_simple_file(mem, phys_device); + mem_remove_simple_file(mem, removable); + unregister_memory(mem, section); + } return 0; } Index: linux-next/include/linux/memory.h =================================================================== --- linux-next.orig/include/linux/memory.h 2010-09-27 09:17:20.000000000 -0500 +++ linux-next/include/linux/memory.h 2010-09-27 09:22:56.000000000 -0500 @@ -19,10 +19,13 @@ #include <linux/node.h> #include <linux/compiler.h> #include <linux/mutex.h> +#include <asm/atomic.h> struct memory_block { unsigned long phys_index; unsigned long state; + atomic_t section_count; + /* * This serializes all state change requests. It isn't * held during creation because the control files are
Add a section count property to the memory_block struct to track the number of memory sections that have been added/removed from a memory block. This allows us to know when the last memory section of a memory block has been removed so we can remove the memory block. Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com> --- drivers/base/memory.c | 16 ++++++++++------ include/linux/memory.h | 3 +++ 2 files changed, 13 insertions(+), 6 deletions(-)