From mboxrd@z Thu Jan 1 00:00:00 1970 From: mkl@pengutronix.de (Marc Kleine-Budde) Date: Thu, 20 Jun 2013 10:43:33 +0200 Subject: BUG: commit "ARM: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW on pre-ARMv6 CPUs" breaks armv5 with CONFIG_PREEMPT Message-ID: <51C2C0B5.8020802@pengutronix.de> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hello Catalin, on current linus/master on armv5 we observed stack trashing[1] on high load. I bisected this problem down to commit: > b9d4d42ad901cc848ac87f1cb8923fded3645568 is the first bad commit > commit b9d4d42ad901cc848ac87f1cb8923fded3645568 > Author: Catalin Marinas > Date: Mon Nov 28 21:57:24 2011 +0000 > > ARM: Remove __ARCH_WANT_INTERRUPTS_ON_CTXSW on pre-ARMv6 CPUs > > This patch removes the __ARCH_WANT_INTERRUPTS_ON_CTXSW definition for > ARMv5 and earlier processors. On such processors, the context switch > requires a full cache flush. To avoid high interrupt latencies, this > patch defers the mm switching to the post-lock switch hook if the > interrupts are disabled. > > Reviewed-by: Will Deacon > Tested-by: Will Deacon > Reviewed-by: Frank Rowand > Tested-by: Marc Zyngier > Signed-off-by: Catalin Marinas > > :040000 040000 034899bdcbc9aa59b5455a85a9d78b646b4cf784 ecc23e33a4ca807d4153f87fbea85a9437ff2928 M arch The problem can be reproduced on several mx28 and an at91sam9263 and only occurs of CONFIG_PREEMPT (Preemptible Kernel (Low-Latency Desktop)) is enabled. I have the gut feeling that the "if (irqs_disabled())" check in the above patch is not correct for CONFIG_PREEMPT. Marc [1] The test program creating 150 threads in a row crashes like this: > [8]+ Segmentation fault ./thread_test_c > [5] Illegal instruction ./thread_test_c > [4] Illegal instruction ./thread_test_c > [2] Segmentation fault ./thread_test_c > [3] Illegal instruction ./thread_test_c > [1] Segmentation fault ./thread_test_c -- Pengutronix e.K. | Marc Kleine-Budde | Industrial Linux Solutions | Phone: +49-231-2826-924 | Vertretung West/Dortmund | Fax: +49-5121-206917-5555 | Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de | -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 259 bytes Desc: OpenPGP digital signature URL: