Messages in this thread | | | Date | Mon, 25 Sep 2017 16:04:07 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH 2/5] x86/intel_rdt: Add diagnostics when writing the schemata file |
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On Mon, 18 Sep 2017, Luck, Tony wrote: > @@ -208,14 +241,19 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of, > char *tok, *resname; > int closid, ret = 0; > > + seq_buf_clear(&last_cmd_status); > + > /* Valid input requires a trailing newline */ > - if (nbytes == 0 || buf[nbytes - 1] != '\n') > + if (nbytes == 0 || buf[nbytes - 1] != '\n') { > + seq_buf_puts(&last_cmd_status, "no trailing newline\n"); > return -EINVAL; > + } > buf[nbytes - 1] = '\0';
In all other instances you access last_cmd_status within the rdtgroup_kn_lock_live() protected section, which also serializes the show() function via rdtgroup_mutex. Here you do it outside for obvious reasons, but that opens a can of evil worms ...
Can you please provide and use two helpers - last_cmd_buf_clear() and last_cmd_buf_puts() - which both have a lockdep_assert_held(&rdtgroup_mutex) inside to make sure that we don't end up with unprotected access accidentally?
Thanks,
tglx
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