Race condition in ofi_get_core_info due to global log_prefix variable in libfabric v1.22.0

[piotrchmiel]

Describe the bug
A race condition occurs in the ofi_get_core_info function in the libfabric library (v1.22.0). Specifically, the global variable log_prefix is modified at line 317 without thread safety, leading to issues when fi_getinfo is called simultaneously from multiple threads.

To Reproduce
Steps to reproduce the behavior:

1. Use libfabric v1.22.0 with the RXD utility provider in conjunction with verbs.
2. Have multiple threads where for example one calls fi_getinfo and another calls fi_fabric.
3. Run the application.
4. Observe race condition warnings or crashes flagged by thread sanitizer.

Expected behavior
Per the documentation, fi_getinfo should be thread-safe and callable simultaneously by multiple threads without serialization. Modifications to the global variable log_prefix should not cause a race condition

Output
Thread sanitizer identifies a race condition when modifying the global variable log_prefix during simultaneous calls to fi_getinfo and other operations.

Code Reference
The problematic function is:

int ofi_get_core_info(uint32_t version, const char *node, const char *service,
                      uint64_t flags, const struct util_prov *util_prov,
                      const struct fi_info *util_hints,
                      const struct fi_info *base_attr,
                      ofi_map_info_t info_to_core, struct fi_info **core_info)
{
    struct fi_info *core_hints = NULL;
    int ret;

    ret = ofi_info_to_core(version, util_prov->prov, util_hints, base_attr,
                           info_to_core, &core_hints);
    if (ret)
        return ret;

    log_prefix = util_prov->prov->name;  // <-- Global variable modified here

    ret = fi_getinfo(version, node, service, flags | OFI_CORE_PROV_ONLY,
                     core_hints, core_info);

    log_prefix = "";  // <-- Global variable reset here

    fi_freeinfo(core_hints);
    return ret;
}

Environment:

• OS: ubuntu22.04
• Provider: RXD utility provider with verbs.
• Libfabric version: 1.22.0

Additional Context
The log_prefix variable is shared across threads, which leads to undefined behavior when multiple threads modify it simultaneously. This violates the thread-safety guarantees of fi_getinfo. A possible fix could involve using thread-local storage for log_prefix to avoid contention between threads.

[dsciebu]

I prepared a patch for this issue: #10568.