[Boost-users] Using boost atomics on data residing in shared memory

Subject: [Boost-users] Using boost atomics on data residing in shared memory
From: Philip Windle (philip.windle_at_[hidden])
Date: 2012-04-03 05:35:39

Is atomicity guaranteed on data residing in shared memory?

E.g. Processes allocate shared memory as follows using either create_only and truncate or open_only:

#define SHARED_MEM_SIZE sizeof(boost::uint32_t)
#define SHARED_MEM_NAME "SHMTest"

boost::shared_ptr<shared_memory_object> shm_obj;
boost::shared_ptr<mapped_region> mapping;
std::string sharedMemoryName(SHARED_MEM_NAME);

shm_obj.reset(new shared_memory_object(create_only, sharedMemoryName.c_str(), read_write));

shm_obj->truncate(SHARED_MEM_SIZE);

mapping.reset(new mapped_region(*shm_obj, read_write, 0, SHARED_MEM_SIZE));

Then, they use the boost atomic functions to read and write to the memory:

volatile boost::uint32_t* temp = static_cast<volatile boost::uint32_t*>(mapping->get_address());

unsigned int value = boost::interprocess::detail::atomic_read32(temp);

boost::interprocess::detail::atomic_write32(temp, value);

Are these memory accesses guaranteed to be atomic? Platform is Linux if that makes a difference.

Thanks

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