[patch] Remove needless delay in MCA rendezvous While testing the MCA recovery code, noticed that some machines would have a five second delay rendezvousing cpus. What was happening is that ia64_wait_for_slaves() would check to see if all the slave CPUs had rendezvoused. If any had not, it would wait 1 millisecond then check again. If any CPUs had still not rendezvoused, it would wait 5 seconds before checking again. On some configs the rendezvous takes more than 1 millisecond, causing the code to wait the full 5 seconds, even though the last CPU rendezvoused after only a few milliseconds. The fix is to check every 1 millisecond to see if all the cpus have rendezvoused. After 5 seconds the code concludes the CPUs will never rendezvous (same as before). The MCA code is, by definition, not performance critical, but a needless delay of 5 seconds is senseless. The 5 seconds also adds up quickly when running the error injection code in a loop. This patch both simplifies the code and removes the needless delay. Signed-off-by: Russ Anderson <rja@xxxxxxx> --- arch/ia64/kernel/mca.c | 41 +++++++++++++++++++---------------------- 1 file changed, 19 insertions(+), 22 deletions(-) Index: test/arch/ia64/kernel/mca.c =================================================================== --- test.orig/arch/ia64/kernel/mca.c 2007-09-20 10:23:57.011455209 -0500 +++ test/arch/ia64/kernel/mca.c 2007-09-20 10:24:00.463872304 -0500 @@ -1136,30 +1136,27 @@ no_mod: static void ia64_wait_for_slaves(int monarch, const char *type) { - int c, wait = 0, missing = 0; - for_each_online_cpu(c) { - if (c == monarch) - continue; - if (ia64_mc_info.imi_rendez_checkin[c] == IA64_MCA_RENDEZ_CHECKIN_NOTDONE) { - udelay(1000); /* short wait first */ - wait = 1; - break; + int c, i , wait; + + /* + * wait 5 seconds total for slaves (arbitrary) + */ + for (i = 0; i < 5000; i++) { + wait = 0; + for_each_online_cpu(c) { + if (c == monarch) + continue; + if (ia64_mc_info.imi_rendez_checkin[c] + == IA64_MCA_RENDEZ_CHECKIN_NOTDONE) { + udelay(1000); /* short wait */ + wait = 1; + break; + } } + if (!wait) + goto all_in; } - if (!wait) - goto all_in; - for_each_online_cpu(c) { - if (c == monarch) - continue; - if (ia64_mc_info.imi_rendez_checkin[c] == IA64_MCA_RENDEZ_CHECKIN_NOTDONE) { - udelay(5*1000000); /* wait 5 seconds for slaves (arbitrary) */ - if (ia64_mc_info.imi_rendez_checkin[c] == IA64_MCA_RENDEZ_CHECKIN_NOTDONE) - missing = 1; - break; - } - } - if (!missing) - goto all_in; + /* * Maybe slave(s) dead. Print buffered messages immediately. */ -- Russ Anderson RAS group SGI rja@xxxxxxx - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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