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On Fri, Feb 06, 2004 at 04:12:24AM -0300, Werner Almesberger wrote: > Section 2.9.7 of the "Austin" draft of IEEE Std. 1003.1-200x, > 28-JUL-2000, says: > > "[...] read( ) [...] shall be atomic with respect to each other > in the effects specified in IEEE Std. 1003.1-200x when they > operate on regular files. If two threads each call one of these > functions, each call shall either see all of the specified > effects of the other call, or none of them." This reads: "all of the specified effects of the other call, or none of them." If I read that correctly, if f_pos is at N, and threads A and B concurrently read M bytes, then each thread's read() must either start at f_pos = N or f_pos = N+M, but never at N < f_pos < N+M. So as long as our code doesn't partially update f_pos, it is valid. Of course, that doesn't change the possible race updating f_pos at the end of each thread's call. Joel -- "In a crisis, don't hide behind anything or anybody. They're going to find you anyway." - Paul "Bear" Bryant Joel Becker Senior Member of Technical Staff Oracle Corporation E-mail: joel.becker@oracle.com Phone: (650) 506-8127 - 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/ | ||||||||||||
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