On 19/09/2016 20:06, Emilio G. Cota wrote: > On Mon, Sep 19, 2016 at 16:51:38 +0100, Alex Bennée wrote: >> > ThreadSanitizer detects a possible race between reading/writing the >> > hashes. As ordering semantics are already documented for qht we just >> > need to ensure a race can't tear the hash value so we can use the >> > relaxed atomic_set/read functions. > This was discussed here: > > https://lists.gnu.org/archive/html/qemu-devel/2016-05/msg03658.html > > To reiterate: reading torn hash values is fine, since the retry will > happen regardless (and all pointers[] remain valid through the RCU > read-critical section).
True, but C11 says data races are undefined, not merely unspecified. seqlock-protected data requires a relaxed read and write, because they are read concurrently in the read and write sides. Paolo
