Hi All,
I am crossposting to networking-discuss and tools-compilers because I am not
sure if this is a compiler issue or a bug in the rpc module:
While chasing another issue related to the RPC connection manager, I noticed
that on my x64 development box, tuning rpcmod:clnt_max_conns had no effect.
Irrespective of which value I set it to, the RPC client would only open one
connection. I could not observe this issue on a Solaris8 SPARC machine.
This issue kept me busy for a day (me questioning my understanding of the code),
until I finally inspected the assembler code of the function in question. Here's
an annotated piece of code (from connmgr_get in uts/common/rpc/clnt_cots.c),
disassembled with mdb:
1863 /*
1864 * If we are at the maximum number of connections to
1865 * the server, hand back the least recently used one.
1866 */
1867 if (i == clnt_max_conns) {
connmgr_get+0x2c4: cmpl $0x1,%ebx
connmgr_get+0x2c7: jle +0xbe <connmgr_get+0x38b>
Apparently, the compiler has optimized
463 #define CLNT_MAX_CONNS 1 /* concurrent connections between
clnt/srvr */
464 static int clnt_max_conns = CLNT_MAX_CONNS;
into a constant value of 1 for clnt_max_conns.
When I recompiled rpcmod with clnt_max_conns declared as int (without static),
the issue was fixed, and assembler code looked OK:
connmgr_get+0x2c4: movl +0x47dae5e(%rip),%eax <clnt_max_conns>
connmgr_get+0x2ca: cmpl %eax,%ebx
connmgr_get+0x2cc: jle +0xbe <connmgr_get+0x390>
My question is: Is this a compiler issue or a genuine bug?
Due to various other constraints, I used my antique snv_98 onnv bldenv with spro
11 (cc: Sun C 5.8 Patch 121016-05 2007/01/10).
Any pointers are highly appreciated. If this is not a compiler bug, I'd open a
bug and prepare a webrev with the fix. If this issue is fixed with current
compilers, I apologize for the noise.
Cheers,
Nils
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