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Date: Wed, 23 May 2012 13:19:14 +0900 From: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> To: Steven Rostedt <rostedt@...dmis.org> Cc: Ingo Molnar <mingo@...e.hu>, Masami Hiramatsu <mhiramat@...hat.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH] Use test_and_clear_bit() instead atomic_dec_and_test() for stop_machine OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> writes: >> The down side to this is that it adds 4 more bytes on a 64bit >> machine. (sizeof(unsigned log) == 8 and sizeof(atomic_t) == 4) Another patch without additional 4bytes. This simply change atomic_dec_and_test() to atomic_xchg(). Thanks. -- OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> stop_machine_first is just to see if it is first one or not. In this usage, atomic_dec_and_test() makes value less than 0. I think it is not desirable, because it only triggers atomic_dec_and_test() less than 0 debug patch. (the patch tests result of atomic_dec_and_test() is < 0) So, this uses atomic_xchg() instead. Signed-off-by: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp> --- arch/x86/kernel/alternative.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff -puN arch/x86/kernel/alternative.c~stop_machine-use-atomic_xchg arch/x86/kernel/alternative.c --- linux/arch/x86/kernel/alternative.c~stop_machine-use-atomic_xchg 2012-05-23 13:10:03.000000000 +0900 +++ linux-hirofumi/arch/x86/kernel/alternative.c 2012-05-23 13:10:03.000000000 +0900 @@ -664,7 +664,7 @@ static int __kprobes stop_machine_text_p struct text_poke_param *p; int i; - if (atomic_dec_and_test(&stop_machine_first)) { + if (atomic_xchg(&stop_machine_first, 0)) { for (i = 0; i < tpp->nparams; i++) { p = &tpp->params[i]; text_poke(p->addr, p->opcode, p->len); _ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.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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