Hi Herbert, On 04/26/2017 10:44 PM, Herbert Xu wrote: > On Tue, Apr 25, 2017 at 10:48:22AM -0400, David Miller wrote: >> From: Florian Westphal <f...@strlen.de> >> Date: Tue, 25 Apr 2017 16:17:49 +0200 >> >>> I'd have less of an issue with this if we'd be talking about >>> something computationally expensive, but this is about storing >>> an extra value inside a struct just to avoid one "shr" in insert path... >> >> Agreed, this shift is probably filling an available cpu cycle :-) > > OK, but we need to have an extra field for another reason anyway. > The problem is that we're not capping the total number of elements > in the hashtable when max_size is not set, this means that nelems > can overflow which will cause havoc with the automatic shrinking > when it tries to fit 2^32 entries into a minimum-sized table. > > So I'm taking that hole back for now :) > > ---8<--- > When max_size is not set or if it set to a sufficiently large > value, the nelems counter can overflow. This would cause havoc > with the automatic shrinking as it would then attempt to fit a > huge number of entries into a tiny hash table. > > This patch fixes this by adding max_elems to struct rhashtable > to cap the number of elements. This is set to 2^31 as nelems is > not a precise count. This is sufficiently smaller than UINT_MAX > that it should be safe. > > When max_size is set max_elems will be lowered to at most twice > max_size as is the status quo. > > Signed-off-by: Herbert Xu <herb...@gondor.apana.org.au>
This commit: https://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/commit/?id=6d684e54690caef45cf14051ddeb7c71beeb681b makes my ARMv7 (32-bit) system panic on boot with the log below. I can test net-next (or net) and report back if you want me to test anything. Thanks! [ 0.158619] futex hash table entries: 1024 (order: 4, 65536 bytes) [ 0.166386] NET: Registered protocol family 16 [ 0.179596] Kernel panic - not syncing: rtnetlink_init: cannot initialize rtnetlink [ 0.179596] [ 0.189350] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.11.0-rc8-02028-g6d684e54690c #37 [ 0.197908] Hardware name: Broadcom STB (Flattened Device Tree) [ 0.204254] [<c020fa18>] (unwind_backtrace) from [<c020b294>] (show_stack+0x10/0x14) [ 0.212447] [<c020b294>] (show_stack) from [<c04bc454>] (dump_stack+0x90/0xa4) [ 0.220144] [<c04bc454>] (dump_stack) from [<c02ab684>] (panic+0xf0/0x270) [ 0.227460] [<c02ab684>] (panic) from [<c0c2705c>] (rtnetlink_init+0x24/0x1d4) [ 0.235145] [<c0c2705c>] (rtnetlink_init) from [<c0c27630>] (netlink_proto_init+0x124/0x148) [ 0.244124] [<c0c27630>] (netlink_proto_init) from [<c02017f8>] (do_one_initcall+0x40/0x168) [ 0.253072] [<c02017f8>] (do_one_initcall) from [<c0c00dfc>] (kernel_init_freeable+0x164/0x200) [ 0.262304] [<c0c00dfc>] (kernel_init_freeable) from [<c087bfd8>] (kernel_init+0x8/0x110) [ 0.270970] [<c087bfd8>] (kernel_init) from [<c0207fa8>] (ret_from_fork+0x14/0x2c) [ 0.279014] CPU1: stopping [ 0.281916] CPU: 1 PID: 0 Comm: swapper/1 Not tainted 4.11.0-rc8-02028-g6d684e54690c #37 [ 0.290499] Hardware name: Broadcom STB (Flattened Device Tree) [ 0.296796] [<c020fa18>] (unwind_backtrace) from [<c020b294>] (show_stack+0x10/0x14) [ 0.305018] [<c020b294>] (show_stack) from [<c04bc454>] (dump_stack+0x90/0xa4) [ 0.312684] [<c04bc454>] (dump_stack) from [<c020e984>] (handle_IPI+0x170/0x190) [ 0.320531] [<c020e984>] (handle_IPI) from [<c020144c>] (gic_handle_irq+0x88/0x8c) [ 0.328586] [<c020144c>] (gic_handle_irq) from [<c020bd78>] (__irq_svc+0x58/0x74) [ 0.336543] Exception stack(0xee055f68 to 0xee055fb0) [ 0.341938] 5f60: 00000001 00000000 ee055fc0 c0219b60 ee054000 c1603cc8 [ 0.350661] 5f80: c1603c6c 00000000 00000000 c1486188 ee055fc0 c1603cd4 c1483408 ee055fb8 [ 0.359323] 5fa0: c0208a40 c0208a44 60000013 ffffffff [ 0.364745] [<c020bd78>] (__irq_svc) from [<c0208a44>] (arch_cpu_idle+0x38/0x3c) [ 0.372613] [<c0208a44>] (arch_cpu_idle) from [<c0255e98>] (do_idle+0x168/0x204) [ 0.380479] [<c0255e98>] (do_idle) from [<c02561ac>] (cpu_startup_entry+0x18/0x1c) [ 0.388493] [<c02561ac>] (cpu_startup_entry) from [<002014ec>] (0x2014ec) [ 0.395687] CPU3: stopping [ 0.398606] CPU: 3 PID: 0 Comm: swapper/3 Not tainted 4.11.0-rc8-02028-g6d684e54690c #37 [ 0.407242] Hardware name: Broadcom STB (Flattened Device Tree) [ 0.413564] [<c020fa18>] (unwind_backtrace) from [<c020b294>] (show_stack+0x10/0x14) [ 0.421795] [<c020b294>] (show_stack) from [<c04bc454>] (dump_stack+0x90/0xa4) [ 0.429495] [<c04bc454>] (dump_stack) from [<c020e984>] (handle_IPI+0x170/0x190) [ 0.437394] [<c020e984>] (handle_IPI) from [<c020144c>] (gic_handle_irq+0x88/0x8c) [ 0.445475] [<c020144c>] (gic_handle_irq) from [<c020bd78>] (__irq_svc+0x58/0x74) [ 0.453406] Exception stack(0xee059f68 to 0xee059fb0) [ 0.458792] 9f60: 00000001 00000000 ee059fc0 c0219b60 ee058000 c1603cc8 [ 0.467489] 9f80: c1603c6c 00000000 00000000 c1486188 ee059fc0 c1603cd4 c1483408 ee059fb8 [ 0.476177] 9fa0: c0208a40 c0208a44 60000013 ffffffff [ 0.481581] [<c020bd78>] (__irq_svc) from [<c0208a44>] (arch_cpu_idle+0x38/0x3c) [ 0.489474] [<c0208a44>] (arch_cpu_idle) from [<c0255e98>] (do_idle+0x168/0x204) [ 0.497331] [<c0255e98>] (do_idle) from [<c02561ac>] (cpu_startup_entry+0x18/0x1c) [ 0.505369] [<c02561ac>] (cpu_startup_entry) from [<002014ec>] (0x2014ec) [ 0.512562] CPU2: stopping [ 0.515463] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 4.11.0-rc8-02028-g6d684e54690c #37 [ 0.524047] Hardware name: Broadcom STB (Flattened Device Tree) [ 0.530368] [<c020fa18>] (unwind_backtrace) from [<c020b294>] (show_stack+0x10/0x14) [ 0.538573] [<c020b294>] (show_stack) from [<c04bc454>] (dump_stack+0x90/0xa4) [ 0.546195] [<c04bc454>] (dump_stack) from [<c020e984>] (handle_IPI+0x170/0x190) [ 0.554050] [<c020e984>] (handle_IPI) from [<c020144c>] (gic_handle_irq+0x88/0x8c) [ 0.562096] [<c020144c>] (gic_handle_irq) from [<c020bd78>] (__irq_svc+0x58/0x74) [ 0.570044] Exception stack(0xee057f68 to 0xee057fb0) [ 0.575465] 7f60: 00000001 00000000 ee057fc0 c0219b60 ee056000 c1603cc8 [ 0.584145] 7f80: c1603c6c 00000000 00000000 c1486188 ee057fc0 c1603cd4 c1483408 ee057fb8 [ 0.592806] 7fa0: c0208a40 c0208a44 60000013 ffffffff [ 0.598220] [<c020bd78>] (__irq_svc) from [<c0208a44>] (arch_cpu_idle+0x38/0x3c) [ 0.606103] [<c0208a44>] (arch_cpu_idle) from [<c0255e98>] (do_idle+0x168/0x204) [ 0.613960] [<c0255e98>] (do_idle) from [<c02561ac>] (cpu_startup_entry+0x18/0x1c) [ 0.621990] [<c02561ac>] (cpu_startup_entry) from [<002014ec>] (0x2014ec) [ 0.629201] ---[ end Kernel panic - not syncing: rtnetlink_init: cannot initialize rtnetlink [ 0.629201] -- Florian
